Patent Publication Number: US-2020302821-A1

Title: Welding simulator

Description:
RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 15/795,312, filed on Oct. 27, 2017, which is a continuation of U.S. patent application Ser. No. 14/615,637, filed on Feb. 6, 2015, now U.S. Pat. No. 9,836,987, which claims priority to and any benefit of U.S. Provisional Patent Application No. 61/940,221 filed on Feb. 14, 2014, the entire contents of which are incorporated herein by reference in their entireties. 
     Each of the following commonly-assigned U.S. patents is incorporated by reference herein in its entirety: 
     (1) U.S. Pat. No. 8,747,116, which issued on Jun. 10, 2014 and is titled System And Method Providing Arc Welding Training In A Real-Time Simulated Virtual Reality Environment Using Real-Time Weld Puddle Feedback; 
     (2) U.S. Pat. No. 8,915,740, which issued on Dec. 23, 2014 and is titled Virtual Reality Pipe Welding Simulator; 
     (3) U.S. Pat. No. 9,483,959, which issued on Nov. 1, 2016 and is titled Welding Simulator; 
     (4) U.S. Pat. No. 8,657,605, which issued on Feb. 25, 2014 and is titled Virtual Testing And Inspection Of A Virtual Weldment; 
     (5) U.S. Pat. No. 9,011,154, which issued on Apr. 21, 2015 and is titled Virtual Welding System; and 
     (6) U.S. Pat. No. 8,911,237, which issued on Dec. 16, 2014 and is titled Virtual Reality Pipe Welding Simulator And Setup. 
    
    
     FIELD 
     The present invention pertains to systems for simulating a welding environment, and more particularly to simulated welding environments that emulate the welding of a weld joint in real time and the setup thereof. 
     BACKGROUND 
     For decades companies have been teaching welding skills. Traditionally, welding has been taught in a real-world setting, that is to say that welding has been taught by actually striking an arc with an electrode on a piece of metal. Instructors, skilled in the art, oversee the training process making corrections in some cases as the trainee performs a weld. By instruction and repetition, a new trainee learns how to weld using one or more processes. However, costs are incurred with every weld performed, which varies depending on the welding process being taught. 
     In more recent times, cost saving systems for training welders have been employed. Some systems incorporate a motion analyzer. The analyzer includes a physical model of a weldment, a mock electrode, and sensing means that track movement of the mock electrode. A report is generated that indicates to what extent the electrode tip traveled outside an acceptable range of motion. More advanced systems incorporate the use of virtual reality, which simulates manipulation of a mock electrode in a virtual setting. Similarly, these systems track position and orientation. Such systems teach only muscle memory, but cannot teach the more advanced welding skills required of a skilled welder. 
     SUMMARY 
     The general inventive concepts encompass systems for simulating welding activity within a simulated welding environment. 
     In one exemplary embodiment, a welding simulator comprises: a logic processor based subsystem operable to execute coded instructions for generating an interactive welding environment in which a welding activity is simulated, the welding activity occurring at an interface of a first simulated work piece and a second simulated work piece defining a simulated weld joint; a display operatively connected to the logic processor based subsystem for visually depicting the interactive welding environment; a first hand-held input device for performing a first simulated welding activity on the simulated weld joint in real time; and a second hand-held input device for performing a second simulated welding activity on the simulated weld joint in real time, wherein at least a portion of the first simulated welding activity and at least a portion of the second simulated welding activity are performed simultaneously. 
     In one exemplary embodiment, the first simulated work piece is at least one of a flat plate and a cylindrical body. In one exemplary embodiment, the cylindrical body is a pipe. 
     In one exemplary embodiment, the second simulated work piece is at least one of a flat plate and a cylindrical body. In one exemplary embodiment, the cylindrical body is a pipe. 
     In one exemplary embodiment, at least one of the first simulated welding activity and the second simulated welding activity includes a tie-in operation. 
     In one exemplary embodiment, the display depicts at least a portion of the simulated weld joint. 
     In one exemplary embodiment, the interactive welding environment is a virtual reality environment. 
     In one exemplary embodiment, the display is integrated in a welding helmet. 
     In one exemplary embodiment, a method of simulating a welding activity is provided. The method comprises: generating an interactive welding environment in which the welding activity is simulated, the welding activity occurring at an interface of a first simulated work piece and a second simulated work piece defining a simulated weld joint; displaying the interactive welding environment including at least a portion of the simulated weld joint; displaying and/or tracking movement of a first hand-held input device performing a first simulated welding activity on the simulated weld joint in real time; and displaying and/or tracking movement of a second hand-held input device performing a second simulated welding activity on the simulated weld joint in real time, wherein at least a portion of the first simulated welding activity and at least a portion of the second simulated welding activity are performed simultaneously. 
     In one exemplary embodiment, the first simulated work piece is at least one of a flat plate and a cylindrical body. In one exemplary embodiment, the cylindrical body is a pipe. 
     In one exemplary embodiment, the second simulated work piece is at least one of a flat plate and a cylindrical body. In one exemplary embodiment, the cylindrical body is a pipe. 
     In one exemplary embodiment, at least one of the first simulated welding activity and the second simulated welding activity includes a tie-in operation. 
     In one exemplary embodiment, the interactive welding environment is a virtual reality environment. 
     In one exemplary embodiment, the display is integrated in a welding helmet. 
     In one exemplary embodiment, a welding simulator comprises: a logic processor based subsystem operable to execute coded instructions for generating an interactive welding environment in which a welding activity is simulated, the welding activity occurring at an interface of a first simulated work piece and a second simulated work piece defining a simulated weld joint; a display operatively connected to the logic processor based subsystem for visually depicting the interactive welding environment; and a hand-held input device for performing a simulated welding activity on the simulated weld joint in real time, wherein the simulated welding activity includes traversing a weld path corresponding to the simulated weld joint, and wherein the weld path comprises a non-linear portion. 
     In one exemplary embodiment, the weld path further comprises a linear portion. 
     In one exemplary embodiment, the weld path further comprises a first linear portion and a second linear portion, wherein the first linear portion and the second linear portion connect to form an angle θ, and wherein 0 degrees&lt;θ&lt;180 degrees. 
     In one exemplary embodiment, the weld path comprises a first non-linear portion and a second non-linear portion. 
     In one exemplary embodiment, the first non-linear portion is connected to the second non-linear portion. 
     In one exemplary embodiment, a linear portion is situated between the first non-linear portion and the second non-linear portion. 
     In one exemplary embodiment, a welding simulator comprises: a logic processor based subsystem operable to execute coded instructions for generating an interactive welding environment in which a welding activity is simulated, the welding activity occurring at an interface of a first simulated work piece and a second simulated work piece defining a simulated weld joint; a display operatively connected to the logic processor based subsystem for visually depicting the interactive welding environment; and a hand-held input device for performing a simulated welding activity on the simulated weld joint in real time, wherein the welding simulator is operable to simulate removal of material from at least one of the first simulated work piece and the second simulated work piece. 
     In one exemplary embodiment, the simulated removal of material occurs during the welding activity. In one exemplary embodiment, the simulated removal of material results from simulating burning through at least one of the first simulated work piece and the second simulated work piece. 
     In one exemplary embodiment, the simulated removal of material results from simulating grinding of the simulated weld joint. 
     In one exemplary embodiment, a welding simulator comprises: a logic processor based subsystem operable to execute coded instructions for generating an interactive welding environment in which a welding activity is simulated, the welding activity occurring at an interface of a first simulated work piece and a second simulated work piece defining a simulated weld joint; a display operatively connected to the logic processor based subsystem for visually depicting the interactive welding environment; and a hand-held input device for performing a simulated welding activity on the simulated weld joint in real time, wherein the welding simulator is operable to simulate generation of smoke during the welding activity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an end user operator engaging in virtual welding activity with a simulator, according to an exemplary embodiment; 
         FIG. 2  is a front view of a simulator, according to an exemplary embodiment; 
         FIG. 3A  is a chart showing pipe welding positions; 
         FIG. 3B  is a chart showing plate welding positions; 
         FIG. 4  is a schematic block diagram of a representation of a simulator, according to an exemplary embodiment; 
         FIG. 5  is a side perspective view of a mock welding tool, according to an exemplary embodiment; 
         FIG. 6  is a close-up view of a welding user interface, according to an exemplary embodiment; 
         FIG. 7  is a close-up view of an observer display device, according to an exemplary embodiment; 
         FIG. 8A  is a perspective view of a personalized display device, according to an exemplary embodiment; 
         FIG. 8B  is a perspective view of the personalized display device of  FIG. 8A  worn by an end user; 
         FIG. 8C  is a perspective view of a personalized display device mounted in a welding helmet, according to an exemplary embodiment; 
         FIG. 9  is a perspective view of a spatial tracker, according to an exemplary embodiment; 
         FIG. 10  is a perspective view of a stand for holding welding coupons, according to an exemplary embodiment; 
         FIG. 11  is a perspective view of an exemplary pipe welding coupon; 
         FIG. 12  is a perspective view of a pipe welding coupon mounted into the stand, according to an exemplary embodiment; 
         FIGS. 13A-13C  illustrate an exemplary embodiment of a boss weld joint; 
         FIG. 13D  illustrates another exemplary embodiment of a boss weld joint; 
         FIG. 14  depicts a simulated welding operation on the boss weld joint of  FIGS. 13A-13B  in a virtual environment, according to an exemplary embodiment; 
         FIG. 15  illustrates an exemplary pipe welding coupon; 
         FIGS. 16A-16E  illustrate an exemplary embodiment of a tie-in operation; 
         FIG. 17  is a subsystem block diagram of a logic processor-based subsystem, according to an exemplary embodiment; 
         FIG. 18  is a block diagram of a graphics processing unit (GPU) of the logic processor-based subsystem, according to an exemplary embodiment; 
         FIG. 19  is a functional block diagram of a welding simulator, according to an exemplary embodiment; 
         FIG. 20  is a flow chart of an exemplary method of training using a virtual reality training system; 
         FIGS. 21A-21B  illustrate the concept of a welding pixel (wexel) displacement map; 
         FIG. 22  illustrates an exemplary embodiment of a coupon space and a weld space of a flat welding coupon simulated in the simulator; 
         FIG. 23  illustrates an exemplary embodiment of a coupon space and a weld space of a corner welding coupon simulated in the simulator; 
         FIG. 24  illustrates an exemplary embodiment of a coupon space and a weld space of a pipe welding coupon simulated in the simulator; 
         FIG. 25  illustrates another exemplary pipe welding coupon; 
         FIGS. 26A-26C  illustrate the concept of a dual-displacement puddle model of the simulator, according to an exemplary embodiment; 
         FIG. 27  illustrates an exemplary orbital welding system as used in an orbital welding environment; 
         FIG. 28  illustrates an exemplary welding tractor for use with the orbital welding system of  FIG. 27 ; 
         FIG. 29  illustrates an exemplary power source and controller of the orbital welding system of  FIG. 27 ; and 
         FIG. 30  illustrates an exemplary pendant for use with the orbital welding system of  FIG. 27 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings wherein the showings are for purposes of illustrating embodiments of the invention only and not for purposes of limiting the same,  FIGS. 1 and 2  show a system for simulating welding depicted generally at  10 , termed herein as simulator  10  or system  10 . Simulator  10  is capable of generating a simulated environment  15 , which may depict a welding setting similar to that in the real world. In some exemplary embodiments, the simulated environment  15  may be a virtual reality environment. By way of example only, various embodiments of the simulator  10  will be described herein with respect to a virtual reality environment, such that the simulator  10  implements virtual reality arc welding (VRAW). Within the virtual environment  15 , simulator  10  facilitates interaction with one or more end user(s)  12 . An input device  155  is included that allows an end user  12  to engage in real-world activity, which is tracked by the simulator  10  and translated into virtual activity. The virtual environment  15  thus comprises an interactive virtual welding environment  15 . A display  200  is included that provides visual access into the virtual environment  15  and the end user&#39;s  12  activity. In one embodiment, simulator  10  may include a display  150  viewable by a plurality of end users  12  or other observers. Additionally, simulator  10  may include a personalized display  140  adapted for use by a single end user  12 , which may be a trainee user  12   a  or an instructor user  12   b.  It is expressly noted here that the end user&#39;s  12  activity in the real world is translated into virtual welding activity and viewed on one or more displays  140 ,  150  in real time. As used herein, the term “real time” means perceiving and experiencing, in time, a virtual environment in the same way that an end user  12  would perceive and experience, in time, a real-world setting. 
     In generating the simulated welding environment  15  (e.g., an interactive virtual welding environment), simulator  10  emulates one or more welding processes for a plurality of weld joints in different welding positions, and additionally emulates the effects of different kinds of electrodes for the plurality of joint configurations. In one particular embodiment, simulator  10  generates an interactive virtual welding environment  15  that emulates welding of a boss weld joint such as typically encountered during pipe welding and/or welding of open root joints. 
     As used herein, “boss weld joint” generally refers to the welding interface between a first work piece and a second work piece, wherein at least one of the work pieces will typically have a round, contoured, or angled portion. As a result, at least a portion of the welding interface will typically be non-linear. In some embodiments, one of the work pieces will have a tab, flange, protrusion, or the like (i.e., a “boss”) that forms part of the welding interface. For example, a weld nut may include a boss portion that facilitates welding the weld nut to another work piece or surface. Such a boss, however, is not required to fall within the definition of “boss weld joint” as used herein. For example, the interface between a round pipe abutting a flat plate or the interface between two sections of pipe are also examples of a boss weld joint. For purposes of further describing the general inventive concepts, the boss joint welding process will generally be described herein in the context of welding a pipe to a flat plate. 
     The system is capable of simulating a weld puddle having real-time molten metal fluidity and heat dissipation characteristics. The simulator  10  is also capable of modeling how virtual welding activity affects the weld joint, e.g., the underlying base material. Illustratively, simulator  10  may emulate welding a root pass and a hot pass, as well as subsequent filler and cap passes, each with characteristics paralleling real-world scenarios. Each subsequent pass may weld significantly different from that of the previous pass as a result of changes in the base material made during the previous pass and/or as a result of a differently selected electrode. Real-time feedback of the puddle modeling allows the end user  12  to observe the virtual welding process on the display  200  and adjust or maintain his/her technique as the virtual weld is being performed. Examples of the kinds of virtual indicators observed may include: flow of the weld puddle, shimmer of molten puddle, changes in color during puddle solidification, freeze rate of the puddle, color gradients of heat dissipation, sound, bead formation, weave pattern, formation of slag, undercut, porosity, spatter, slag entrapment, overfill, blowthrough, and occlusions to name a few. It is to be realized that the puddle characteristics are dependent upon, that is to say responsive to, the end user&#39;s  12  movement of the input device  155 . In this manner, the displayed weld puddle is representative of a real-world weld puddle formed in real time based on the selected welding process and on the end user&#39;s  12  welding technique. Furthermore, “wagon tracks” is the visual trail of weld defects and slag left behind in the toes of the root pass made during boss joint (e.g., pipe) welding using the SMAW process. The second pass in the boss joint welding, called the hot pass, must be hot enough to remelt the wagon tracks so they are eliminated in the final weldment. Also, wagon tracks may be removed by a grinding process. Such wagon tracks and elimination of the wagon tracks are properly simulated in the simulator  10  described herein, in accordance with an exemplary embodiment of the invention. 
     With continued reference to  FIGS. 1 and 2  and now also to  FIGS. 3A and 3B , simulator  10  may emulate welding processes in various welding positions and model how the weld puddle reacts in each position. More specifically, simulator  10  may emulate boss joint (e.g., pipe) welding in vertical, horizontal, and/or inclined positions referred to in the art respectively as the 5G, 2G, and 6G positions. Additionally, simulator  10  may emulate welding in a 1G position which relates to the rotating horizontal position of the pipe, or in a 4G position which relates to welding overhead as may be associated with a groove weld in abutting plates. Other welding positions may relate to the welding of open root joints for various configurations of flat plate. It is to be understood that the simulator  10 , including a modeling and analysis engine to be described in detail in subsequent paragraphs, takes into account the effects of gravity on the weld puddle. Accordingly, the weld puddle reacts differently, for example, for a welding pipe in a 5G position from that of a 6G position. The examples above are not to be construed as limiting, but are included for illustrative purposes. Those skilled in the art will readily understand its application to any weld joint, welding position, or type of weldment including different kinds of base material. 
     With reference now to  FIGS. 2 and 4 , simulator  10  includes a logic processor-based subsystem  110 , which may be programmable and operable to execute coded instructions for generating the interactive virtual welding environment  15 . Simulator  10  further includes sensors and/or sensor systems, which may be comprised of a spatial tracker  120 , operatively connected to the logic processor-based subsystem  110 . Simulator  10  also includes a welding user interface  130  in communication with the logic processor-based subsystem  110  for set up and control of the simulator  10 . As referenced above, display device(s)  200  are included, which may comprise a face-mounted display device  140  and an observer display device  150  each connected to the logic processor-based subsystem  110  providing visual access to the interactive virtual welding environment  15  and simulated activity therein. One or more of the display devices  200  may be connected to the spatial tracker  120  for changing the images viewed on the device in response to its position and/or movement thereof, as described below. 
     Input Device 
     With reference now to  FIG. 5 , as mentioned above, simulator  10  includes an input device  155  that facilitates interaction with the end-user  12 . In one embodiment, input device  155  comprises a mock welding tool  160 . The mock welding tool  160  may be, but does not have to be, fashioned to resemble a real-world welding tool such as, for example, a manual welding electrode holder or a weld gun delivering a continuous feed to electrode (e.g., MIG, FCAW, GTAW welding tools). Still, other configurations of the mock welding tool  160  may be implemented without departing from the intended scope of coverage of the embodiments of the subject invention. For discussion purposes, the embodiments of the subject invention will be described in the context of using a mock welding tool  160  that resembles a manual welding electrode holder  156 . The mock welding tool  160  may closely resemble a real-world welding tool. In one particular embodiment, mock welding tool  160  may have the same shape, weight, and feel as a real-world welding tool. In fact, a real welding tool could be used as the mock welding tool  160  to provide the actual feel of the tool in the user&#39;s hands, even though, in the simulator  10 , the real welding tool would not be used to actually create a real arc. In this manner, end-user  12 , which maybe a trainee user  12   a,  becomes accustomed to handling a real-world welding tool thereby enhancing the virtual welding experience. However, the mock welding tool  160  may be constructed in any manner and configuration chosen with sound judgment. 
     Illustratively, mock welding tool  160  simulates a stick welding tool for pipe welding and includes a holder  161  and a simulated stick electrode  162  extending therefrom. The simulated stick electrode  162  may include a tactilely resistive tip  163  to simulate resistive feedback that occurs during welding in a real-world setting. If the end user  12  moves the simulated stick electrode  162  too far back out of the root (described in detail below), the end user  12  will be able to feel or sense the reduced resistance thereby deriving feedback for use in adjusting or maintaining the current welding process. It is contemplated that the stick welding tool may incorporate an actuator, not shown, that withdraws the simulated stick electrode  162  during the virtual welding process. That is to say that as end user  12  engages in virtual welding activity, the distance between holder  161  and the tip of the simulated stick electrode  162  is reduced to simulate consumption of the electrode. The consumption rate, i.e., withdrawal of the stick electrode  162 , may be controlled by the logic processor-based subsystem  110  and more specifically by coded instructions executed by the logic processor-based subsystem  110 . The simulated consumption rate may also depend on the end user&#39;s  12  technique. It is noteworthy to mention here that as simulator  10  facilitates virtual welding with different types of electrodes, the consumption rate or reduction of the stick electrode  162  may change with the welding procedure used and/or setup of the simulator  10 . 
     The actuator of the mock welding tool  160  may be electrically driven. Power for engaging the actuator may come from the simulator  10 , from an external power source, or from internal battery power. In one embodiment, the actuator may be an electromotive device, such as an electric motor. Still, any type of actuator or form of motive force may be used including, but not limited to, electromagnetic actuators, pneumatic actuators, mechanical actuators, or spring-loaded actuators, in any combination thereof. 
     As indicated above, the mock welding tool  160  may work in conjunction with the spatial tracker for interacting with the simulator  10 . In particular, the position and/or orientation of mock welding tool  160  may be monitored and tracked by the spatial tracker  120  in real time. Data representing the position and orientation may therefore be communicated to the logic processor-based subsystem  110  and modified or converted for use as required for interacting with the virtual welding environment  15 . 
     Spatial Tracker 
     Referencing  FIG. 9 , an example of a spatial tracker  120  is illustrated. Spatial tracker  120  may interface with the logic processor-based subsystem  110 . In one embodiment, the spatial tracker  120  may track the mock welding tool  160  magnetically. That is to say that the spatial tracker generates a magnetic envelope, which is used to determine position and orientation, as well as speed and/or changes in speed. Accordingly, in some exemplary embodiments, the spatial tracker  120  includes a magnetic source  121  and source cable, one or more sensors  122 , host software on disk  123 , a power source  124 , USB and RS-232 cables  125 , a processor tracking unit  126 , and other associated cables. The magnetic source  121  is capable of being operatively connected to the processor tracking unit  126  via cables, as are the one or more sensors  122 . The power source  124  is also capable of being operatively connected to the processor tracking unit  126  via a cable. The processor tracking unit  126  is capable of being operatively connected to the logic processor-based subsystem  110  via a USB or RS-232 cable  125 . The host software on disk  123  may be loaded onto the logic processor-based subsystem  110  and allows functional communication between the spatial tracker  120  and the logic processor-based subsystem  110 . 
     The magnetic source  121  creates a magnetic field, or envelope, surrounding the source  121  defining a three-dimensional space within which the end user&#39;s  12  activity may be tracked for interacting with the simulator  10 . The envelope establishes a spatial frame of reference. Objects used within the envelope, e.g., mock welding tool  160  and coupon stand (described below), may be comprised of non-metallic, i.e., non-ferric and non-conductive, material so as not to distort the magnetic field created by the magnetic source  121 . Each sensor  122  may include multiple induction coils aligned in crossing spatial directions, which may be substantially orthogonally aligned. The induction coils measure the strength of the magnetic field in each of the three directions providing information to the processor tracking unit  126 . In one embodiment at least one sensor  122  is attached to the mock welding tool  160  allowing the mock welding tool  160  to be tracked with respect to the spatial frame of reference in both position and orientation. More specifically, the induction coils may be mounted in the tip of the electrode  162 . In this way, simulator  10  is able to determine where within the three-dimensional envelope the mock welding tool  160  is positioned. Additional sensors  122  may be provided and operatively attached to the one or more display devices  200 . Accordingly, simulator  10  may use sensor data to change the view seen by the end user  12  responsive to the end user&#39;s  12  movements. As such, the simulator  10  captures and tracks the end user&#39;s  12  activity in the real world for translation into the simulated welding environment  15 . 
     In accordance with another exemplary embodiment of the invention, the sensor(s)  122  may wirelessly interface to the processor tracking unit  126 , and the processor tracking unit  126  may wirelessly interface to the logic processor-based subsystem  110 . In accordance with yet another exemplary embodiments of the invention, other types of spatial trackers  120  may be used in the simulator  10  including, for example, an accelerometer/gyroscope-based tracker, an optical tracker, an infrared tracker, an acoustic tracker, a laser tracker, a radio frequency tracker, an inertial tracker, an active or passive optical tracker, and augmented reality based tracking. Still, other types of trackers may be used without departing from the intended scope of coverage of the general inventive concepts. 
     Display Device 
     With reference now to  FIG. 8A , an example of the face-mounted display device  140  will now be described. The face-mounted display device  140  may be integrated into a welding helmet  900 , as shown in  FIG. 8C  or alternatively may be separately mounted as shown in  FIG. 8B . The face-mounted display device  140  may include two high-contrast SVGA 3D OLED micro-displays capable of delivering fluid full-motion video in the 2D and frame sequential video modes. Virtual images (e.g., video) from the virtual welding environment  15  are provided and displayed on the face-mounted display device  140 . In one embodiment of the subject invention, the logic processor-based subsystem  110  provides stereoscopic video to the face-mounted display device  140 , enhancing the depth perception of the user. Stereoscopic images may be produced by a logic processing unit, which may be a graphics processing unit described in detail below. A zoom (e.g.,2×) mode may also be provided, allowing a user to simulate a cheater plate. 
     The face-mounted display device  140  operatively connects to the logic processor-based subsystem  110  and the spatial tracker  120  via wired or wireless means. A sensor  122  of the spatial tracker  120  may be attached to the face-mounted display device  140  or to the welding helmet  900  thereby allowing the face-mounted display device  140  to be tracked with respect to the 3D spatial frame of reference created by the spatial tracker  120 . In this way, movement of the welding helmet  900  responsively alters the image seen by the end user  12  in the simulated welding environment  15  (e.g., a three-dimensional virtual reality setting). The face-mounted display device  140  may also function to call up and display menu items similar to that of observer display device  150 , as subsequently described. In this manner, an end user is therefore able to use a control on the mock welding tool  160  (e.g., a button or switch) to activate and select options from the menu. This may allow the user to easily reset a weld if the user makes a mistake, change certain parameters, or back up to re-do a portion of a weld bead trajectory, for example. 
     The face-mounted display device  140  may further include speakers  910 , allowing the user to hear simulated welding-related and environmental sounds produced by the simulator  10 . Sound content functionality and welding sounds provide particular types of welding sounds that change depending on if certain welding parameters are within tolerance or out of tolerance. Sounds are tailored to the various welding processes and parameters. For example, in a MIG spray arc welding process, a crackling sound is provided when the user does not have the mock welding tool  160  positioned correctly, and a hissing sound is provided when the mock welding tool  160  is positioned correctly. In a short arc welding process, a hissing sound is provided when undercutting is occurring. These sounds mimic real-world sounds corresponding to correct and incorrect welding techniques. 
     High fidelity sound content may be taken from real-world recordings of actual welding using a variety of electronic and mechanical means. The perceived volume and direction of the sound is modified depending on the position, orientation, and distance of the end user&#39;s head, i.e., the face-mounted display device  140 , with respect to the simulated arc between the mock welding tool  160  and the welding coupon  175 . Sound may be provided to the user via speakers  910 , which may be earbud speakers or any other type of speakers or sound generating device, mounted in the face-mounted display device  140  or alternatively mounted in the console  135  and/or stand  170 . Still, any manner of presenting sound to the end user  12  while engaging in virtual welding activity may be chosen. It is also noted here that other types of sound information may be communicated through the speakers  910 . Examples include verbal instructions from the instructor user  12   b,  in either real time or via prerecorded messages. Prerecorded messages may be automatically triggered by particular virtual welding activity. Real time instructions may be generated on site or from a remote location. Still, any type of message or instruction may be conveyed to end user  12 . 
     Console 
     With reference now to  FIGS. 2, 6, and 7 , the simulator  10  may include a console  135  housing one or more components of the simulator  10 . In one embodiment, the console  135  may be constructed to resemble a welding power source. That is to say that the shape and size of the console  135  may match that of a real-world device. Operation of the simulator  10  may be facilitated by a welding unit interface  130 , which may be fashioned to resemble welding power source knobs, dials, and/or switches  133 ,  134 . Simulator  10  may further include a display, which may be display device  200 . Coded instructions, i.e., software, installed onto the simulator  10  may direct the end user&#39;s  12  interaction with the simulator  10  by displaying instructions and/or menu options on the display  200 . Interaction with the simulator  10  may include functions relating to administrative activity, simulation set up and activation, and the like. This may further include selection of a particular welding process and electrode type, as well as part set up including welding position. Selections made by way of welding unit interface  130  are reflected on the display  200 . 
       FIG. 6  illustrates an exemplary embodiment of the console  135  and welding user interface  130 . The welding unit interface  130  may include a set of buttons  131  corresponding to the user selections  153  used during set up and operation of the simulator  10 . The buttons  131  may be colored to correspond to colors of the user selections  153  displayed on display  200 . When one of the buttons  131  is pressed, a signal is sent to the logic processor-based subsystem  110  to activate the corresponding function. The welding unit interface  130  may also include a joystick  132  capable of being used by a user to select various parameters and selections displayed on the display  200 . The welding unit interface  130  further includes a dial or knob  133 , which in an exemplary manner, may be used for adjusting wire feed speed/amps, and another dial or knob  134  for adjusting volts/trim. The welding unit interface  130  also includes a dial or knob  136  for selecting an arc welding process. In accordance with an exemplary embodiment of the invention, three arc welding processes are selectable including flux cored arc welding (FCAW), gas metal arc welding (GMAW), and shielded metal arc welding (SMAW). The welding unit interface  130  further includes a dial or knob  137  for selecting a welding polarity. In accordance with an exemplary embodiment of the invention, three arc welding polarities are selectable including alternating current (AC), positive direct current (DC+), and negative direct current (DC−). Still, other welding processes and set up features may be incorporated in the simulator  10  without departing from the intended scope of coverage of the general inventive concepts, including but not limited to TIG welding embodiments. From the aforementioned, it will be readily seen that setup of the simulator  10  parallels set up of a real-world device. 
     The graphical user interface functionality  1213  (see  FIG. 19 ) allows a user, viewable via the observer display device  150  and using the joystick  132  of the physical user interface  130 , to set up a welding scenario. The set up of a welding scenario may include selecting a language, entering an end user name, selecting a practice plate (e.g., a welding coupon, T-plate, flat plate), selecting a welding process (e.g., FCAW, GMAW, SMAW, TIG) and associated axial spray, pulse, or short arc mode of transfer, selecting a gas type and flow rate, selecting a type of stick electrode (e.g., E6010 or E7018), and selecting a type of flux cored wire (e.g., self-shielded, gas-shielded). The set up of a welding scenario may also include setting up a coupon stand  170  to be discussed in detail below. The set up of a welding scenario further includes selecting an environment (e.g., a background environment in virtual reality space), setting a wire feed speed, setting a voltage level, selecting a polarity, and turning particular visual cues on or off. In some embodiments, the setup of a welding scenario may include inputting parameters associated with preheating a work piece (e.g., a thick rod or plate) prior to welding. It is noted here that in one embodiment, limitations may be incorporated into the simulator  10 , which may be software limitations, that prevent operation of a given welding scenario until the appropriate settings for a selected process have been properly entered. In this way, trainee users  12   a  are taught or learn the proper range of real-world welding settings by setting up virtual welding scenarios. 
     Accordingly, display  200  reflects activity corresponding to the end user selections  153  including menu, actions, visual cues, new coupon set up, and scoring. These user selections may be tied to user buttons on the console  135 . As a user makes various selections via display  200 , the displayed characteristics can change to provide selected information and other options to the user. However, the display  200 , which may be an observer display device  150 , may have another function, which is to display virtual images seen by the end user  12  during operation of the simulator  10 , i.e., while engaging in virtual welding activity. Display  200  may be set up to view the same image as seen by the end user  12 . Alternatively, display  200  may also be used to display a different view, or different perspective, of the virtual welding activity. 
     In one embodiment, display devices  150 ,  200  may be used to playback virtual welding activity stored electronically on data storage devices  300 , shown in  FIG. 17 . Data representing the end user&#39;s  12  virtual welding activity may be, for example, stored for playback and review, downloaded for archiving purposes, and/or transmitted to remote locations for viewing and critiquing in real time. In replaying the virtual welding activity, details such as weld puddle fluidity and travel speed, as well as discontinuity states  152  including, for example, improper fillet size, poor bead placement, poor tie-in, concave bead, excessive convexity, undercut, porosity, incomplete fusion, slag entrapment, excess spatter, and burn-through, may be represented. Undercut may also be displayed, which is the result of an out of tolerance angle. Moreover, porosity may be displayed caused by moving the arc too far away from the weldment. In this manner, the simulator  10  is capable of replaying part or all of particular virtual welding activity and modeling all aspects of the virtual welding scenario including occlusions and defects related directly to the end user&#39;s activity. 
     Referencing  FIG. 7 , simulator  10  is also capable of analyzing and displaying the results of virtual welding activity. By analyzing the results, it is meant that simulator  10  is capable of determining when during the welding pass (including any tie-ins) and where along the weld joints the end user  12  deviated from the acceptable limits of the welding process. A score may be attributed to the end user&#39;s  12  performance. In one embodiment, the score may be a function of deviation in position, orientation, and speed of the mock welding tool  160  through ranges of tolerances, which may extend from an ideal welding pass to marginal or unacceptable welding activity. Any gradient of ranges may be incorporated into the simulator  10  as chosen for scoring the end user&#39;s  12  performance. Scoring may be displayed numerically or alpha-numerically. Additionally, the end user&#39;s  12  performance may be displayed graphically showing, in time and/or position along the weld joint, how closely the mock welding tool traversed the weld joint. Parameters such as travel angle, work angle, speed, and distance from the weld joint are examples of what may be measured, although any parameters may be analyzed for scoring purposes. For example, performance of a tie-in procedure, as described herein, can be analyzed and scored. The tolerance ranges of the parameters are taken from real-world welding data, thereby providing accurate feedback as to how the end user will perform in the real world. In another embodiment, analysis of the defects corresponding to the end user&#39;s  12  performance may also be incorporated and displayed on the display devices  150 ,  200 . In this embodiment, a graph may be depicted indicating what type of discontinuity resulted from measuring the various parameters monitored during the virtual welding activity. While occlusions may not be visible on the display  200 , defects may still have occurred as a result of the end user&#39;s  12  performance, the results of which may still be correspondingly displayed, e.g., graphed. 
     Display  200  may also be used to display tutorial information used to train an end user  12 . Examples of tutorial information may include instructions, which may be displayed graphically as depicted by video or pictures. Additionally, instructions may be written or presented in audio format, as mentioned above. Such information may be stored and maintained on the data storage devices  300 . In one embodiment, simulator  10  is capable of displaying virtual welding scenes showing various welding parameters  151  including position, tip to work, weld angle, travel angle, and travel speed, termed herein as visual cues. 
     In one embodiment, remote communications may be used to provide virtual instruction by offsite personnel, i.e., remote users, working from similarly or dissimilarly constructed devices, i.e., simulators. Portraying a virtual welding process may be accomplished via a network connection including but not limited to the internet, LANs, and other means of data transmission. Data representing a particular weld (including performance variables) may be sent to another system capable of displaying the virtual image and/or weld data. It should be noted that the transmitted data is sufficiently detailed for allowing remote user(s) to analyze the welder&#39;s performance. Data sent to a remote system may be used to generate a virtual welding environment thereby recreating a particular welding process. Still, any way of communicating performance data or virtual welding activity to another device may be implemented without departing from the intended scope of coverage of the embodiments of the subject invention. 
     Welding Coupon 
     With reference now to  FIGS. 1, 11, and 12 , simulator  10  may include a welding coupon  175  that resembles pipe sections juxtaposed to form a welding joint  176 . The welding coupon  175  may work in conjunction with the simulator  10 , serving as a guide for the end user  12  while engaging in virtual welding activity (e.g., welding of a boss weld joint). A plurality of welding coupons  175  may be used, that is to say interchanged for use in a given cycle of virtual welding activity. The types of welding coupons may include cylindrical pipe sections, arcuate pipe segments, flat plate, T-plate, and solid rods, just to name a few. In one embodiment, each of the welding coupons may incorporate open root joints or grooves. However, any configurations of weld joints may be incorporated into a welding coupon without departing from the intended scope of coverage of the embodiments of the subject invention. 
     The dimensions of welding coupons  175  may vary. For cylindrical pipe, the range of inside diameters may extend, for example, from 1½ inches (inside diameter) to 18 inches (inside diameter). In one particular embodiment, the range of inside diameters may exceed 18 inches. In another embodiment, arcuate pipe segments may have a characteristic radius in the range extending, for example, from 1½ inches (inside diameter) up to and exceeding 18 inches (inside diameter). Furthermore, it is to be construed that any inside diameter of welding coupon  175  may be utilized, both those smaller than 1½ inches and those exceeding 18 inches. In a practical sense, any size of welding coupon  175  can be used as long as the welding coupon  175 , or a portion of the welding coupon  175 , fits within the envelope generated by the spatial tracker  120 . Flat plate may extend up to and exceed 18 inches in length as well. Still, it is to be understood that the upper dimensional limits of a welding coupon  175  are constrained only by the size and strength of the sensing field generated by the spatial tracker  120  and its ability to be positioned respective of the welding coupon  175 . All such variations are to be construed as falling within the scope of coverage of the embodiments of the subject invention. 
     In one embodiment, the welding coupon  175  includes a pipe  2000  or pipe section interfaced with a plate  2002  that is flat, planar, or the like. In this manner, the welding coupon  175  can emulate a pipe-on-plate weld, as a type of boss weld (see  FIGS. 13A-13B and 15 ). An outer circumference of where the pipe  2000  interfaces with or otherwise contacts the plate  2002  forms a weld path  2004 . A shape of the weld path  2004  will typically correspond to a shape of the pipe  2000 . The weld path  2004  is a path that a mock welding tool  2010  (e.g., the mock welding tool  160 ) is expected to traverse when welding the pipe  2000  and plate  2002  to one another. 
     In one exemplary embodiment, the pipe  2000  and the plate  2002  interface to form a fillet joint (see  FIGS. 13A-13B ).  FIG. 13A  is a side elevational view of the pipe  2000  and the plate  2002 .  FIG. 13B  is a perspective view of the pipe  2000  and the plate  2002 .  FIG. 13C  is a perspective view, according to an alternative exemplary embodiment, of a solid rod  2001  and the plate  2002  with the mock welding tool  2010  in position to weld along the weld path  2004 . 
     In another exemplary embodiment, the solid rod  2001  and the plate  2002  interface to form a fillet joint, wherein a first mock welding tool  2012  and a second mock welding tool  2014  are welding along the weld path  2004  at the same time (see  FIG. 13D ). Thus, the simulator  10  is capable of simulating simultaneous welding activity on a single weld joint in real time. 
       FIG. 14  is an image  2100  showing how the simulated operation of welding the fillet joint at the interface of the pipe  2000  and the plate  2002  might look to a user (e.g., the user  12 ). For example, the image  2100  could be displayed on any suitable display device (e.g., the display  200 ). In this manner, the image  2100  could be displayed on the observer display device  150 . Furthermore, the image  2100  shows what the user might see in his/her face-mounted display device  140 . 
     In one embodiment, a lower section  2020  of the pipe  2000  includes a beveled or grooved section to form a groove joint (see  FIG. 15 ). Thus, the pipe  2000  and the plate  2002  interface to form the grooved joint.  FIG. 15  is a perspective view of the pipe  2000  and the plate  2002 . 
     When welding certain weld joints, such as the fillet joint of  FIGS. 13A-13C , the groove joint of  FIG. 15 , a corner joint, or the like, including straight/linear weld joints, an experienced welder may be able to traverse the entire weld path (e.g., the weld path  2004 ) in a single pass. However environmental obstacles or other constraints (e.g., fatigue, distraction) may require that a user only traverse a portion of the weld path, stop momentarily (e.g., to reposition his/her body relative to the weld), and then resume traversing the weld path. Likewise, an inexperienced welder (e.g., the trainee welder  12   a ) may feel more comfortable or otherwise benefit from breaking up a long weld pass (e.g., a 360 degree weld pass) into two or more smaller weld passes (e.g., a first 180 degrees weld pass and a second 180 degree weld pass). The joining or connecting of two different weld passes is called a tie-in. 
     In one embodiment, a tie-in operation  2300  (e.g., as shown in  FIGS. 16A-16E ) is emulated in the simulator  10 . In this manner, the tie-in operation can be performed and practiced/taught, scored, etc. As shown in  FIG. 16A , the weld path  2004  for the fillet joint at the interface of the pipe  2000  and the plate  2002  (see  FIG. 13B ) is circular. In welding the fillet joint, the user positions the mock welding tool  2010  to begin welding at a first point  2302  on the weld path  2004  (see  FIG. 16B ). The user then moves the mock welding tool  2010  along the weld path  2004  in the direction of the arrow  2304 . The user moves the mock welding tool  2010  along the weld path  2004  until a second point  2306  is reached, at which time welding is temporarily suspended, thereby completing a first weld pass  2308  (see  FIG. 16C ). Typically, the first weld pass will substantially solidify during this period of non-welding. 
     As the user prepares to begin a second weld pass  2326 , it is important that the second weld pass  2326  is tied-in to the first weld pass  2308 . Accordingly, the user positions the mock welding tool  2010  to begin welding at a third point  2320  on the weld path  2004  that at least partially overlaps the second point  2306  on the weld path  2004  where the first weld pass  2308  ended (see  FIG. 16D ). By beginning the second weld pass  2326  at a point that at least partially overlaps or is otherwise merged with the first weld pass  2308 , the second weld pass  2326  will be tied-in with the first weld pass  2308 . The user then moves the mock welding tool  2010  along the weld path  2004  in the direction of the arrow  2322 . The user moves the mock welding tool  2010  along the weld path  2004  until a fourth point  2324  is reached, at which time welding is halted, thereby completing the second weld pass  2326  (see  FIG. 16E ). Again, given the circular nature of this particular weld path  2004 , the fourth point  2324  on the weld path  2004  at least partially overlaps with the first point  2302  on the weld path  2004 . 
     The first weld pass  2308  and the second weld pass  2326 , which are tied-in to one another, form the fillet joint weld between the pipe  2000  and the plate  2002 . 
     As mentioned above, the welding coupon  175  may be constructed from a material that does not interfere with the spatial tracker  120 . For spatial trackers generating a magnetic field, the welding coupon  175  may be constructed from non-ferrous and non-conductive material (e.g., plastic). However, any type of material may be chosen that is suitable for use with the type of spatial tracker  120  or other sensors selected. 
     Referencing  FIGS. 11-12, 13A-13C, and 15 , the welding coupon  175  may be constructed so that it fits into a table or stand  170 , which functions (at least in part) to hold the welding coupon  175  constant with respect to the spatial tracker  120 . Accordingly, the welding coupon  175  may include a connecting portion  177  or connector  177 , as shown in  FIGS. 11-12 . The connecting portion  177  may extend from one side of the welding coupon  175 , which as illustrated may be the bottom side (e.g., a bottom surface of the plate  2002 ), and may be received into a mechanical interlocking device included with the stand  170 . It will be appreciated that the orientation at which the welding coupon  175  is inserted into the stand  170  may need to be constant, i.e., repeatable, for closely matching the virtual weldment, e.g., pipe, created within the virtual welding environment  15 . In this manner, as long as the simulator  10  is aware of how the position of the welding coupon  175  has changed, adjustments to the virtual counterpart may be made accordingly. For example, during set up, the end user  12  may select the size of the part (e.g., pipe) to be welded on. The end user  12  may then insert the appropriate welding coupon  175  into the stand  170 , locking it into position. Subsequently, the end user  12  may choose a desired welding position making the selection via the welding user interface  130 . As will be described below, the stand  170  may then be tilted or adjusted to position the welding coupon  175  in any of the welding positions recognized by the simulator  10 . Of course, it will be appreciated that adjusting the position of the welding coupon  175  also adjusts the position of the spatial tracker  120  thereby preserving the relative position of the welding coupon  175  within the sensory tracking field. 
       FIG. 10  depicts one embodiment of the stand  170 . The stand  170  may include an adjustable table  171 , a stand base  172 , an adjustable arm  173 , and a vertical post  174 . The table  171  and the arm  173  are respectively attached to the vertical post  174 . The table  171  and the arm  173  are each capable of being adjusted along the height of the vertical post  174 , which may include upward, downward, and/or rotational movement with respect to the vertical post  174 . The arm  173  is used to hold the welding coupon  175 , in a manner consistent with that discussed herein. The table  171  may assist the end user  12  by allowing his/her arms to rest on the table  171  during use. In one particular embodiment, the vertical post  174  is indexed with position information such that a user may know exactly where the arm  173  and the table  171  are positioned. This information may also be entered into the simulator  10  by way of the welding user interface  130  and the display device  150  during set up. 
     An alternative embodiment of the subject invention is contemplated wherein the positions of the table  171  and the arm  173  are automatically adjusted responsive to selections made during set up of the simulator  10 . In this embodiment, selections made via the welding user interface  130  may be communicated to the logic processor-based subsystem  110 . Actuators and feedback sensors employed by the stand  170  may be controlled by the logic processor-based subsystem  110  for positioning the welding coupon  175  without physically moving the arm  173  or the table  171 . In one embodiment, the actuators and feedback sensors may comprise electrically driven servomotors. However, any locomotive device may be used to automatically adjust the position of the stand  170  as chosen with sound engineering judgment. In this manner, the process of setting up the welding coupon  175  is automated and does not require manual adjustment by the end user  12 . 
     Another embodiment of the subject invention includes the use of intelligence devices used in conjunction with the welding coupon  175 , termed herein as “smart” coupons  175 . In this embodiment, the welding coupon  175  includes a device having information about that particular welding coupon  175  that may be sensed by the stand  170 . In particular, the arm  173  may include detectors that read data stored on or within the device located on the welding coupon  175 . Examples may include the use of digital data encoded on a sensor, e.g., micro-electronic device, that may be read wirelessly when brought into proximity of the detectors. Other examples may include the use of passive devices like bar coding. Still any manner of intelligently communicating information about the welding coupon  175  to the logic processor-based subsystem  110  may be chosen with sound engineering judgment. 
     The data stored on the welding coupon  175  may automatically indicate, to the simulator  10 , the kind of welding coupon  175  that has been inserted in the stand  170 . For example, a 2-inch pipe coupon may include information related to its diameter. Alternatively, a flat plate coupon may include information that indicates the kind of weld joint included on the coupon, e.g., a groove weld joint or a butt weld joint, as well as its physical dimensions. In this manner, information about the welding coupon  175  may be used to automate that portion of the setup of the simulator  10  related to selecting and installing a welding coupon  175 . 
     Calibration functionality  1208  (see  FIG. 19 ) provides the capability to match up physical components in real-world space (3D frame of reference) with visual components in the virtual welding environment  15 . Each different type of welding coupon  175  is calibrated in the factory by mounting the welding coupon  175  to the arm  173  of the stand  170  and touching the welding coupon  175  at predefined points  179  (indicated by, for example, three dimples  179  on the welding coupon  175 ) with a calibration stylus operatively connected to the stand  170 . The simulator  10  reads the magnetic field intensities at the predefined points  179 , provides position information to the logic processor-based subsystem  110 , and the logic processor-based subsystem  110  uses the position information to perform the calibration (i.e., the translation from real-world space to virtual reality space). 
     Any part of the same type of welding coupon  175 , accordingly, fits into the arm  173  of the stand  170  in the same repeatable way to within very tight tolerances. Therefore, once a particular type of welding coupon  175  is calibrated, repeated calibration of similar coupons is not necessary, i.e., calibration of a particular type of welding coupon  175  is a one-time event. Stated differently, welding coupons  175  of the same type are interchangeable. Calibration ensures that physical feedback perceived by the user during a welding process matches up with what is displayed to the user in virtual reality space, making the simulation seem more real. For example, if the user slides the tip of a mock welding tool  160  around the corner of an actual welding coupon  175 , the user will see the tip sliding around the corner of the virtual welding coupon on the display  200  as the user feels the tip sliding around the actual corner. In accordance with an exemplary embodiment of the invention, the mock welding tool  160  may also be placed in a pre-positioned jig and calibrated in a similar manner, based on the known jig position. 
     In accordance with another embodiment of the subject invention, “smart” coupons may include sensors that allow the simulator  10  to track the pre-defined calibration point, or corners of the “smart” coupon. The sensors may be mounted on the welding coupon  175  at the precise location of the predefined calibration points. However, any manner of communicating calibration data to the simulator  10  may be chosen. Accordingly, the simulator  10  continuously knows where the “smart” coupon is in real-world 3D space. Furthermore, licensing keys may be provided to “unlock” welding coupons  175 . When a particular welding coupon  175  is purchased, a licensing key may be provided that allows the end user  12   a,    12   b  to enter the licensing key into the simulator  10 , unlocking the software associated with that particular welding coupon  175 . In an alternative embodiment, special nonstandard welding coupons may be made or otherwise provided based on real-world CAD drawings of parts. 
     With reference now to  FIGS. 2, 4, and 10 , as mentioned above, simulator  10  includes a logic processor-based subsystem  110 , which may comprise programmable electronic circuitry  202  for executing coded instructions used to generate the simulated welding environment  15 . The programmable electronic circuitry  202  may include one or more logic processors  203  or logic processor-based systems  203 , which may be comprised of one or more microprocessors  204 . In one particular embodiment, the programmable electronic circuitry  202  may be comprised of central processing unit(s) (CPU) and graphics processing unit(s) (GPU), to be discussed further below. Additional circuitry may be included, like for example electronic memory, i.e., RAM, ROM, as well as other peripheral support circuitry. It is noted that electronic memory may be included for both the CPU and the GPU, each of which may be separately programmable for use in rendering aspects of the simulated welding environment  15  as described herein. Moreover, the programmable electronic circuitry  202  may include and utilize data storage devices  300  such as hard disk drives, optical storage devices, flash memory, and the like. Still other types of electronic circuitry may be included that facilitate the transfer of data between devices within the simulator  10  or between different simulators  10 . This may include, for example, receiving data from one or more input devices  155 , e.g., spatial tracker or sensor, or transferring data over one or more networks which may be a local area network (LAN), a wide area network (WAN), and/or the Internet. It is to be understood that the aforementioned devices and processes are exemplary in nature and should not be construed as limiting. In fact, any form of programmable circuitry, support circuitry, communication circuitry, and/or data storage may be incorporated into the embodiments of the subject invention as chosen with sound engineering judgment. 
       FIG. 17  illustrates an exemplary embodiment of a subsystem block diagram of the logic processor-based subsystem  110  of the simulator  10 . The logic processor-based subsystem  110  may include a central processing unit (CPU)  111  and two graphics processing units (GPU)  115 . The two GPUs  115  may be programmed to provide virtual reality simulation of a weld puddle having real-time molten metal fluidity as well as heat absorption and dissipation characteristics. 
     With reference to  FIG. 18 , a block diagram of the graphics processing unit (GPU)  115  is shown. Each GPU  115  supports the implementation of data parallel algorithms. In accordance with an exemplary embodiment of the invention, each GPU  115  provides two video outputs  118  and  119  capable of providing two virtual reality views. Two of the video outputs may be routed to the face-mounted display device  140 , rendering the welder&#39;s point of view, and a third video output may be routed to the observer display device  150 , for example, rendering either the welder&#39;s point of view or some other point of view. The remaining fourth video output may be routed to a projector, for example, or used for any other purpose suitable for simulating a virtual welding environment  15 . Both GPUs  115  may perform the same welding physics computations but may render the virtual welding environment  15  from the same or different points of view. The GPU  115  includes a computed unified device architecture (CUDA)  116  and a shader  117 . The CUDA  116  is the computing engine of the GPU  115  which is accessible to software developers through industry standard programming languages. The CUDA  116  includes parallel cores and is used to run the physics model of the weld puddle simulation described herein. The CPU  111  provides real-time welding input data to the CUDA  116  on the GPU  115 . In one particular embodiment, the shader  117  is responsible for drawing and applying all of the visuals of the simulation. Bead and puddle visuals are driven by the state of a wexel displacement map which is described later herein. In accordance with an exemplary embodiment of the invention, the physics model runs and updates at a rate of about 30 times per second. 
       FIG. 19  illustrates an exemplary embodiment of a functional block diagram of the simulator  10 . The various functional blocks of the simulator  10  may be implemented largely via software instructions and modules running on the logic processor-based subsystem  110 . The various functional blocks of the simulator  10  include a physical interface  1201 , torch and clamp models  1202 , environment models  1203 , sound content functionality  1204 , welding sounds  1205 , stand/table model  1206 , internal architecture functionality  1207 , calibration functionality  1208 , coupon models  1210 , welding physics  1211 , internal physics adjustment tool (tweaker)  1212 , graphical user interface functionality  1213 , graphing functionality  1214 , student reports functionality  1215 , renderer  1216 , bead rendering  1217 , 3D textures  1218 , visual cues functionality  1219 , scoring and tolerance functionality  1220 , tolerance editor  1221 , and special effects  1222 . 
     The internal architecture functionality  1207  provides the higher level software logistics of the processes of the simulator  10  including, for example, loading files, holding information, managing threads, turning the physics model on, and triggering menus. The internal architecture functionality  1207  runs on the CPU  111 , in accordance with an exemplary embodiment of the invention. Certain real-time inputs to the logic processor-based subsystem  110  include arc location, gun position, face-mounted display device or helmet position, gun on/off state, and contact made state (yes/no). 
     During a simulated welding scenario, the graphing functionality  1214  gathers user performance parameters and provides the user performance parameters to the graphical user interface functionality  1213  for display in a graphical format (e.g., on the observer display device  150 ). Tracking information from the spatial tracker  120  feeds into the graphing functionality  1214 . The graphing functionality  1214  includes a simple analysis module (SAM) and a whip/weave analysis module (WWAM). The SAM analyzes user welding parameters including welding travel angle, travel speed, weld angle, position, and tip to work by comparing the welding parameters to data stored in bead tables. The WWAM analyzes user whipping parameters including dime spacing, whip time, and puddle time. The WWAM also analyzes user weaving parameters including width of weave, weave spacing, and weave timing. The SAM and WWAM interpret raw input data (e.g., position and orientation data) into functionally usable data for graphing. In one exemplary embodiment, the SAM, the WWAM, and/or some other module is used to track, graph, or otherwise account for tie-in operations, as described herein. For each parameter analyzed by the SAM, the WWAM, and/or other related module, a tolerance window is defined by parameter limits around an optimum or ideal set point input into bead tables using the tolerance editor  1221 , and scoring and tolerance functionality  1220  is performed. 
     The tolerance editor  1221  includes a weldometer which approximates material usage, electrical usage, and welding time. Furthermore, when certain parameters are out of tolerance, welding discontinuities (i.e., welding defects) may occur. The state of any simulated welding discontinuities are processed by the graphing functionality  1214  and presented via the graphical user interface functionality  1213  in a graphical format. Such welding discontinuities include fillet size, poor bead placement, improper tie-in, concave bead, excessive convexity, undercut, porosity, incomplete fusion, slag entrapment, and excess spatter. In accordance with an exemplary embodiment of the invention, the level or amount of a discontinuity is dependent on how far away a particular user parameter is from the optimum or ideal set point. 
     Different parameter limits may be pre-defined for different types of users such as, for example, welding novices, welding experts, and persons at a trade show. The scoring and tolerance functionality  1220  provide number scores depending on how close to optimum (ideal) a user is for a particular parameter and depending on the level of discontinuities or defects present in the weld. Information from the scoring and tolerance functionality  1220  and from the graphics functionality  1214  may be used by the student reports functionality  1215  to create a performance report for an instructor and/or a student. 
     Visual cues functionality  1219  provide immediate feedback to the user by displaying overlaid colors and indicators on the face-mounted display device  140  and/or the observer display device  150 . Visual cues are provided for each of the welding parameters  151  including position, tip to work, weld angle, travel angle, and travel speed and visually indicate to the user if some aspect of the user&#39;s welding technique should be adjusted based on the predefined limits or tolerances. Visual cues may also be provided for whip/weave technique, weld bead “dime” spacing, and proper tie-in technique, for example. 
     In accordance with an exemplary embodiment of the invention, simulation of a weld puddle or pool in virtual reality space is accomplished where the simulated weld puddle has real-time molten metal fluidity and heat dissipation characteristics. At the heart of the weld puddle simulation is the welding physics functionality  1211  (a.k.a., the physics model) which may be executed on the GPUs  115 , in accordance with an exemplary embodiment of the invention. The welding physics functionality employs a double displacement layer technique to accurately model dynamic fluidity/viscosity, solidity, heat gradient (heat absorption and dissipation), puddle wake, and bead shape, and is described in more detail herein with respect to  FIGS. 21A-21B . 
     The welding physics functionality  1211  communicates with the bead rendering functionality  1217  to render a weld bead in all states from the heated molten state to the cooled solidified state. The bead rendering functionality  1217  uses information from the welding physics functionality  1211  (e.g., heat, fluidity, displacement, dime spacing) to accurately and realistically render a weld bead in virtual reality space in real time. The 3D textures functionality  1218  provides texture maps to the bead rendering functionality  1217  to overlay additional textures (e. g., scorching, slag, grain) onto the simulated weld bead. The renderer functionality  1216  is used to render various non-puddle specific characteristics using information from the special effects module  1222  including sparks, spatter, smoke, arc glow, fumes, and certain discontinuities such as, for example, undercut and porosity. 
     The internal physics adjustment tool  1212  is a tweaking tool that allows various welding physics parameters to be defined, updated, and modified for the various welding processes. In accordance with an exemplary embodiment of the invention, the internal physics adjustment tool  1212  runs on the CPU  111 , and the adjusted or updated parameters are downloaded to the GPUs  115 . The types of parameters that may be adjusted via the internal physics adjustment tool  1212  include parameters related to welding coupons, process parameters that allow a process to be changed without having to reset a welding coupon (allows for doing a second pass), various global parameters that can be changed without resetting the entire simulation, and other various parameters. 
       FIG. 20  is a flow chart of an exemplary embodiment of a method  1300  of training using the simulator  10 . In step  1310 , a mock welding tool is moved with respect to a welding coupon in accordance with a welding technique. In step  1320 , the position and orientation of the mock welding tool is tracked in three-dimensional space using a virtual reality system. In step  1330 , a real-time virtual reality simulation of the mock welding tool and the welding coupon in a virtual reality space is displayed as the simulated mock welding tool deposits a simulated weld bead material onto at least one simulated surface of the simulated welding coupon by forming a simulated weld puddle in the vicinity of a simulated arc emitting from said simulated mock welding tool. In step  1340 , real-time molten metal fluidity and heat dissipation characteristics of the simulated weld puddle are displayed. In step  1350 , at least one aspect of the welding technique is modified in real time in response to viewing the real-time molten metal fluidity and heat dissipation characteristics of the simulated weld puddle. In one exemplary embodiment, the welding technique includes a tie-in operation, as described herein. 
     The method  1300  illustrates how a user is able to view a weld puddle in virtual reality space and modify his/her welding technique in response to viewing various characteristics of the simulated weld puddle, including real-time molten metal fluidity (e.g., viscosity) and heat dissipation. The user may also view and respond to other characteristics including real-time puddle wake and dime spacing. Viewing and responding to characteristics of the weld puddle is how many welding operations are actually performed in the real world. The double displacement layer modeling of the welding physics functionality  1211  running on the GPUs  115  allows for such real-time molten metal fluidity and heat dissipation characteristics to be accurately modeled and represented to the user. For example, heat dissipation determines solidification time (i.e., how much time it takes for a wexel to completely solidify). 
     Furthermore, a user may make a second pass over the weld bead material using the same or a different (e.g., a second) mock welding tool, welding electrode, and/or welding process. In such a second pass scenario, the simulation shows the simulated mock welding tool, the welding coupon, and the original simulated weld bead material in virtual reality space as the simulated mock welding tool deposits a second simulated weld bead material merging with the first simulated weld bead material by forming a second simulated weld puddle in the vicinity of a simulated arc emitting from the simulated mock welding tool. Additional subsequent passes using the same or different welding tools or processes may be made in a similar manner. In any second or subsequent pass, the previous weld bead material is merged (as a form of tie-in) with the new weld bead material being deposited as a new weld puddle is formed in virtual reality space from the combination of any of the previous weld bead material, the new weld bead material, and possibly the underlying coupon material in accordance with certain embodiments of the invention. Such subsequent passes may be performed to repair a weld bead formed by a previous pass, for example, or may include a heat pass and one or more gap closing passes after a root pass as is done in pipe welding. In accordance with various exemplary embodiments of the invention, base and weld bead material may be simulated to include mild steel, stainless steel, and aluminum. 
     As noted above, the merging of multiple weld passes is termed a “tie-in.” The second or subsequent weld pass may be performed parallel to and at least partially on top of a first or prior weld pass. Another type of tie-in is when a weld pass is interrupted or otherwise halted prior to traversing the complete weld path. Thereafter, the user starts a new weld pass on the weld path, wherein the new weld pass overlaps or is otherwise interfaced with the pre-existing weld pass. Thus, a proper tie-in involves correctly merging the two or more weld passes making up the weld along the weld path. 
     In accordance with an exemplary embodiment of the invention, welding with stainless steel materials is simulated in a real-time virtual environment. The base metal appearance is simulated to provide a realistic representation of a stainless steel weldment. Simulation of the visual effect is provided to change the visual spectrum of light to accommodate the coloration of the arc. Realistic sound is also simulated based on proper work distance, ignition, and speed. The arc puddle appearance and deposition appearance are simulated based on the heat affected zone and the torch movement. Simulation of dross or broken particles of aluminum oxide or aluminum nitride films, which can be scattered throughout the weld bead, is provided. Calculations related to the heating and cooling affected zones are tailored for stainless steel welding. Discontinuity operations related to spatter are provided to more closely and accurately simulate the appearance of stainless steel GMAW welding. 
     In accordance with an exemplary embodiment of the invention, welding with aluminum materials is simulated in a real-time virtual environment. The bead wake is simulated to closely match the appearance of the aluminum welding to that seen in the real world. The base metal appearance is simulated to represent a realistic representation of an aluminum weldment. Simulation of the visual effect is provided to change the visual spectrum of light to accommodate the coloration of the arc. A calculation of lighting is provided to create reflectivity. Calculations related to the heating and cooling affected zones are tailored for aluminum welding. Simulation of oxidation is provided to create a realistic “cleaning action.” Realistic sound is also simulated based on proper work distance, ignition, and speed. The arc puddle appearance and deposition appearance are simulated based on the heat affected zone and the torch movement. The appearance of the aluminum wire is simulated in the GMAW torch to provide a realistic and proper appearance. 
     In accordance with an exemplary embodiment of the invention, GTAW welding is simulated in a real-time virtual environment. Simulation of operational parameters for GTAW welding are provided including, but not limited to, flow rate, pulsing frequency, pulse width, arc voltage control, AC balance, and output frequency control. Visual representation of the puddle “splash” or dipping technique and melt off of the welding consumable are also simulated. Furthermore, representations of autogenous (no filler metal) and GTAW with filler metal welding operations in the welding puddle are rendered visually and audibly. Implementation of additional filler metal variations may be simulated including, but not limited to, carbon steel, stainless steel, aluminum, and Chrome Moly. A selectable implementation of an external foot pedal may be provided for operation while welding. 
     Engine for Modeling 
       FIGS. 21A-21B  illustrate the concept of a welding element (wexel) displacement map  1420 , in accordance with an exemplary embodiment of the invention.  FIG. 21A  shows a side view of a flat welding coupon  1400  having a flat top surface  1410 . The welding coupon  1400  exists in the real world as, for example, a plastic part, and also exists in virtual reality space as a simulated welding coupon.  FIG. 21B  shows a representation of the top surface  1410  of the simulated welding coupon  1400  broken up into a grid or array of welding elements, termed “wexels” forming a wexel map  1420 . Each wexel (e.g., wexel  1421 ) defines a small portion of the surface  1410  of the welding coupon. The wexel map defines the surface resolution. Changeable channel parameter values are assigned to each wexel, allowing values of each wexel to dynamically change in real time in virtual reality weld space during a simulated welding process. The changeable channel parameter values correspond to the channels Puddle (molten metal fluidity/viscosity displacement), Heat (heat absorption/dissipation), Displacement (solid displacement), and Extra (various extra states, e.g., slag, grain, scorching, virgin metal). These changeable channels are referred to herein as PHED for Puddle, Heat, Extra, and Displacement, respectively. 
       FIG. 22  illustrates an exemplary embodiment of a coupon space and a weld space of the flat welding coupon  1400  of  FIG. 21A  simulated in the simulator  10  of  FIGS. 1 and 2 . Points  0 , X, Y, and Z define the local 3D coupon space. In general, each coupon type defines the mapping from 3D coupon space to 2D virtual reality weld space. The wexel map  1420  of  FIG. 21B  is a two-dimensional array of values that map to weld space in virtual reality. A user is to weld from point B to point E as shown in  FIG. 22 . A trajectory line from point B to point E is shown in both 3D coupon space and 2D weld space in  FIG. 22 . 
     Each type of coupon defines the direction of displacement for each location in the wexel map. For the flat welding coupon of  FIG. 22 , the direction of displacement is the same at all locations in the wexel map (i.e., in the Z-direction). The texture coordinates of the wexel map are shown as S, T (sometimes called U, V) in both 3D coupon space and 2D weld space, in order to clarify the mapping. The wexel map is mapped to and represents the rectangular surface  1410  of the welding coupon  1400 . 
       FIG. 23  illustrates an exemplary embodiment of a coupon space and a weld space of a corner welding coupon  1600  simulated in the simulator  10 . The corner welding coupon  1600  has two surfaces  1610  and  1620  in 3D coupon space that are mapped to 2D weld space as shown in  FIG. 23 . Again, points  0 , X, Y, and Z define the local 3D coupon space. The texture coordinates of the wexel map are shown as S, T in both 3D coupon space and 2D weld space, in order to clarify the mapping. A user is to weld from point B to point E as shown in  FIG. 23 . A trajectory line from point B to point E is shown in both 3D coupon space and 2D weld space in  FIG. 23 . However, the direction of displacement is towards the line X′- 0 ′ as shown in the 3D coupon space, towards the opposite corner. 
       FIG. 24  illustrates an exemplary embodiment of a coupon space and a weld space of a pipe welding coupon  1700  simulated in the simulator  10 . The pipe welding coupon  1700  has a curved surface  1710  in 3D coupon space that is mapped to 2D weld space. Points  0 , X, Y, and Z once again define the local 3D coupon space. The texture coordinates of the wexel map are shown as S, T in both 3D coupon space and 2D weld space, in order to clarify the mapping. An end user  12  is to weld from point B to point E along a curved trajectory as shown in  FIG. 24 . A trajectory curve and line from point B to point E is shown in 3D coupon space and 2D weld space, respectively. The direction of displacement is away from the line Y- 0  (i.e., away from the center of the pipe).  FIG. 25  illustrates an exemplary embodiment of the pipe welding coupon  1700  of  FIG. 24 . The pipe welding coupon  1700  is made of a non-ferric, non-conductive plastic and simulates two pipe pieces  1701  and  1702  coming together to form a root joint  1703 . An attachment piece  1704  for attaching to the arm  173  of the stand  170  is also shown. 
     In a similar manner that a texture map may be mapped to a rectangular surface area of a geometry, a weldable wexel map may be mapped to a rectangular surface of a welding coupon. Each element of the weldable map is termed a wexel in the same sense that each element of a picture is termed a pixel (a contraction of picture element). A pixel contains channels of information that define a color (e.g., red, green, blue). A wexel contains channels of information (e.g., P, H, E, D) that define a weldable surface in virtual reality space. 
     In accordance with an exemplary embodiment of the invention, the format of a wexel is summarized as channels PHED (Puddle, Heat, Extra, Displacement) which contains four floating point numbers. The Extra channel is treated as a set of bits which store logical information about the wexel such as, for example, whether or not there is any slag at the wexel location. The Puddle channel stores a displacement value for any liquefied metal at the wexel location. The Displacement channel stores a displacement value for the solidified metal at the wexel location. The Heat channel stores a value giving the magnitude of heat at the wexel location. In this way, the weldable part of the coupon can show displacement due to a welded bead, a shimmering surface “puddle” due to liquid metal, color due to heat, etc. All of these effects are achieved by the vertex and pixel shaders applied to the weldable surface. 
     In accordance with an exemplary embodiment of the invention, a displacement map and a particle system are used where the particles can interact with each other and collide with the displacement map. The particles are virtual dynamic fluid particles and provide the liquid behavior of the weld puddle but are not rendered directly (i.e., are not visually seen directly). Instead, only the particle effects on the displacement map are visually seen. Heat input to a wexel affects the movement of nearby particles. There are two types of displacement involved in simulating a welding puddle which include Puddle and Displacement. Puddle displacement is “temporary” and only lasts as long as there are particles and heat present. Displacement is “permanent.” Puddle displacement is the liquid metal of the weld which changes rapidly (e.g., shimmers) and can be thought of as being “on top” of the Displacement. The particles overlay a portion of a virtual surface displacement map (i.e., a wexel map). The Displacement represents the permanent solid metal including both the initial base metal and the weld bead that has solidified. 
     In accordance with an exemplary embodiment of the invention, the simulated welding process in virtual reality space works as follows: Particles stream from the emitter (emitter of the simulated mock welding tool  160 ) in a thin cone. The particles make first contact with the surface of the simulated welding coupon where the surface is defined by a wexel map. The particles interact with each other and the wexel map and build up in real time. More heat is added the nearer a wexel is to the emitter. Heat is modeled in dependence on distance from the arc point and the amount of time that heat is input from the arc. Certain visuals (e.g., color) are driven by the heat. A weld puddle is drawn or rendered in virtual reality space for wexels having enough heat. Wherever it is hot enough, the wexel map liquefies, causing the Puddle displacement to “raise up” for those wexel locations. Puddle displacement is determined by sampling the “highest” particles at each wexel location. As the emitter moves on along the weld trajectory, the wexel locations left behind cool. Heat is removed from a wexel location at a particular rate. When a cooling threshold is reached, the wexel map solidifies. As such, the Puddle displacement is gradually converted to Displacement (i.e., a solidified bead). Displacement added is equivalent to Puddle removed such that the overall height does not change. Particle lifetimes are tweaked or adjusted to persist until solidification is complete. Certain particle properties that are modeled in the simulator  10  include attraction/repulsion, velocity (related to heat), dampening (related to heat dissipation), and direction (related to gravity). 
       FIGS. 26A-26C  illustrate an exemplary embodiment of the concept of a dual-displacement (displacement and particles) puddle model of the simulator  10 . Welding coupons are simulated in virtual reality space having at least one surface. The surfaces of the welding coupon are simulated in virtual reality space as a double displacement layer including a solid displacement layer and a puddle displacement layer. The puddle displacement layer is capable of modifying the solid displacement layer. 
     As described herein, “puddle” is defined by an area of the wexel map where the Puddle value has been raised up by the presence of particles. The sampling process is represented in  FIGS. 26A-26C . A section of a wexel map is shown having seven adjacent wexels. The current Displacement values are represented by un-shaded rectangular bars  1910  of a given height (i.e., a given displacement for each wexel). In  FIG. 26A , the particles  1920  are shown as round un-shaded dots colliding with the current Displacement levels and are piled up. In  FIG. 26B , the “highest” particle heights  1930  are sampled at each wexel location. In  FIG. 26C , the shaded rectangles  1940  show how much Puddle has been added on top of the Displacement as a result of the particles. The weld puddle height is not instantly set to the sampled values since Puddle is added at a particular liquification rate based on Heat. Although not shown in  FIGS. 26A-26C , it is possible to visualize the solidification process as the Puddle (shaded rectangles) gradually shrinks and the Displacement (unshaded rectangles) gradually grows from below to exactly take the place of the Puddle. In this manner, real-time molten metal fluidity characteristics are accurately simulated. As a user practices a particular welding process, the user is able to observe the molten metal fluidity characteristics and the heat dissipation characteristics of the weld puddle in real time in virtual reality space and use this information to adjust or maintain his/her welding technique. 
     The number of wexels representing the surface of a welding coupon is fixed. Furthermore, the puddle particles that are generated by the simulation to model fluidity are temporary, as described herein. Therefore, once an initial puddle is generated in virtual reality space during a simulated welding process using the simulator  10 , the number of wexels plus puddle particles tends to remain relatively constant. This is because the number of wexels that are being processed is fixed and the number of puddle particles that exist and are being processed during the welding process tend to remain relatively constant because puddle particles are being created and “destroyed” at a similar rate (i.e., the puddle particles are temporary). Therefore, the processing load of the logic processor-based subsystem  110  remains relatively constant during a simulated welding session. 
     In accordance with another exemplary embodiment of the invention, puddle particles may be generated within or below the surface of the welding coupon. In such an embodiment, displacement may be modeled as being positive or negative with respect to the original surface displacement of a virgin (i.e., un-welded) coupon. In this manner, puddle particles may not only build up on the surface of a welding coupon, but may also penetrate the welding coupon. However, the number of wexels is still fixed and the puddle particles being created and destroyed is still relatively constant. 
     In accordance with other exemplary embodiments of the invention, instead of modeling particles, a wexel displacement map may be provided having more channels to model the fluidity of the puddle. Or, instead of modeling particles, a dense voxel map may be modeled. Or, instead of a wexel map, only particles may be modeled which are sampled and never go away. Such alternative embodiments may not provide a relatively constant processing load for the system, however. 
     Furthermore, in accordance with an exemplary embodiment of the invention, blowthrough or a keyhole is simulated by taking material away. For example, if a user keeps an arc in the same location for too long, in the real world, the material would burn away causing a hole. Such real-world burnthrough is simulated in the simulator  10  by wexel decimation techniques. If the amount of heat absorbed by a wexel is determined to be too high by the simulator  10 , that wexel may be flagged or designated as being burned away and rendered as such (e.g., rendered as a hole). Subsequently, however, wexel re-constitution may occur for certain welding process (e.g., pipe welding) where material is added back after being initially burned away. In general, the simulator  10  simulates wexel decimation (taking material away) and wexel reconstitution (adding material back). 
     Furthermore, removing material in root-pass welding is properly simulated in the simulator  10 . For example, in the real world, grinding of the root pass may be performed prior to subsequent welding passes. Similarly, simulator  10  may simulate a grinding pass that removes material from the virtual weld joint. It will be appreciated that the material removed is modeled as a negative displacement on the wexel map. That is to say that the grinding pass removes material that is modeled by the simulator  10  resulting in an altered bead contour. Simulation of the grinding pass may be automatic, which is to say that the simulator  10  removes a predetermined thickness of material, which may be respective to the surface of the root pass weld bead. In an alternate embodiment, an actual grinding tool, or grinder, may be simulated that turns on and off by activation of the mock welding tool  160  or another input device. It is noted that the grinding tool may be simulated to resemble a real-world grinder. In this embodiment, the user maneuvers the grinding tool along the root pass to remove material responsive to the movement thereof. It will be understood that the user may be allowed to remove too much material. In a manner similar to that described above, holes or keyholes, or other defects (described above) may result if the user “grinds away” too much material. Still, hard limits or stops may be implemented, i.e. programmed, to prevent the user from removing too much material or indicate when too much material is being removed. 
     In addition to the non-visible “puddle” particles described herein, the simulator  10  also uses three other types of visible particles to represent Arc, Flame, and Spark effects, in accordance with an exemplary embodiment of the invention. These types of particles do not interact with other particles of any type but interact only with the displacement map. While these particles do collide with the simulated weld surface, they do not interact with each other. Only Puddle particles interact with each other, in accordance with an embodiment of the present invention. The physics of the Spark particles is setup such that the Spark particles bounce around and are rendered as glowing dots in virtual reality space. 
     The physics of the Arc particles is setup such that the Arc particles hit the surface of the simulated coupon or weld bead and stay for a while. The Arc particles are rendered as larger dim bluish-white spots in virtual reality space. It takes many such spots superimposed to form any sort of visual image. The end result is a white glowing nimbus with blue edges. 
     The physics of the Flame particles is modeled to slowly raise upward. The Flame particles are rendered as medium sized dim red-yellow spots. It takes many such spots superimposed to form any sort of visual image. The end result is blobs of orange-red flames with red edges raising upward and fading out. Other types of non-puddle particles may be implemented in the simulator  10 , in accordance with other exemplary embodiments of the invention. For example, smoke particles may be modeled and simulated in a similar manner to flame particles. 
     The final steps in the simulated visualization are handled by the vertex and pixel shaders provided by the shaders  117  of the GPUs  115 . The vertex and pixel shaders apply Puddle and Displacement, as well as surface colors and reflectivity altered due to heat, etc. The Extra (E) channel of the PHED wexel format, as discussed earlier herein, contains all of the extra information used per wexel. In accordance with an embodiment of the present invention, the extra information includes a non virgin bit (true=bead, false=virgin steel), a slag bit, an undercut value (amount of undercut at this wexel where zero equals no undercut), a porosity value (amount of porosity at this wexel where zero equals no porosity), and a bead wake value which encodes the time at which the bead solidifies. There are a set of image maps associated with different coupon visuals including virgin steel, slag, bead, and porosity. These image maps are used both for bump mapping and texture mapping. The amount of blending of these image maps is controlled by the various flags and values described herein. 
     A bead wake effect is achieved using a 1D image map and a per wexel bead wake value that encodes the time at which a given bit of bead is solidified. Once a hot puddle wexel location is no longer hot enough to be called “puddle,” a time is saved at that location and is called “bead wake.” The end result is that the shader code is able to use the 1D texture map to draw the “ripples” that give a bead its unique appearance which portrays the direction in which the bead was laid down. In accordance with an alternative embodiment of the present invention, the simulator  10  is capable of simulating, in virtual reality space, and displaying a weld bead having a real-time weld bead wake characteristic resulting from a real-time fluidity-to-solidification transition of the simulated weld puddle, as the simulated weld puddle is moved along a weld trajectory. 
     In accordance with another exemplary embodiment of the invention, the simulator  10  is capable of teaching a user how to troubleshoot a welding machine. For example, a troubleshooting mode of the system may train a user to make sure the user sets up the system correctly (e.g., correct gas flow rate, correct power cord connected). In accordance with another exemplary embodiment of the invention, the simulator  10  is capable of recording and playing back a welding session (or at least a portion of a welding session, for example, N frames). A track ball may be provided to scroll through frames of video, allowing a user or instructor to critique a welding session. Playback may be provided at selectable speeds as well (e.g., full speed, half speed, quarter speed). In accordance with another exemplary embodiment of the invention, a split-screen playback may be provided, allowing two welding sessions to be viewed side-by-side, for example, on the observer display device  150 . For example, a “good” welding session may be viewed next to a “poor” welding session for comparison purposes. 
     Automated welding is also an aspect of the present invention. One illustrative example of automated welding is orbital welding, which is often used for the joining of tubes or pipes of various types of materials. For example, a TIG (GTAW) welding torch may be used to orbit around the pipes to be welded together by an automated mechanical system.  FIG. 27  illustrates an exemplary embodiment of an orbital welding system as used in an orbital welding environment. An orbital welding system includes a welding tractor that travels around the pipes or tubes, a welding power source and controller, and a pendant providing operator control.  FIG. 28  shows the welding tractor  2010  of the orbital welding system of  FIG. 27 , as operably connected to two pipes to be welded.  FIG. 29  shows a power source and controller  2020  of the orbital welding system of  FIG. 27 , and  FIG. 30  shows a pendant  2030  of the orbital welding system of  FIG. 27 . 
     While the above discussion has focused on the virtual reality simulation of various welding processes, including orbital welding, other embodiments of the invention are not limited to that aspect and include teaching and feedback aspects of the actual setup and performance characteristics associated with welds made in accordance with a user-defined setup. As discussed above, GTAW/GMAW welding requires training to ensure that the operator understands the controls which are available for the practice of a welding process, for example, an orbital welding process. There is a misconception that automation associated with orbital welding systems eliminates the need for training, since the machine is doing the welding. Automated orbital welding requires training to ensure the operator understands welding, and all of the unique setup and implementation skills for controlling TIG beads. This includes error correction, larger diameter pipe welding, the utilization of remote cameras, and proper error assessment and correction. 
     Training programs offer inconsistent or insufficient coverage of teaching a good weld situation, a bad weld situation, and the mechanisms to perform, react to, or correct each. Instructors for this type of niche solution are hard to find with sufficient background and/or industry knowledge and experience. Only through quality training taught by certified instructors can operators of welding equipment gain the complex skills needed to meet the strict acceptance criteria in today&#39;s welding environment. Additionally, on large circumference projects with long weld joints (which may include one or more tie-ins), the difficulty of maintaining attention and focus represents a significant problem. 
     In the GTAW process, an electric arc is maintained between the non-consumable tungsten electrode and the work piece. The electrode supports the heat of the arc and the metal of the work piece melts and forms the weld puddle. The molten metal of the work piece and the electrode must be protected against oxygen in the atmosphere, thereby typically employing an inert gas such as argon as the shielding gas. If the addition of a filler metal is used, the filler wire can be fed to the weld puddle, where it melts due to the energy delivered by the electric arc. In accordance with one exemplary embodiment of the invention, a virtual reality welding system is provided that incorporates technology related to viewing a GTAW/GMAW automated welding operation, using a pendant (actual or virtual) or remote control as it relates to automated welding, identifying welding discontinuities based upon chosen welding parameter combinations, and correcting operator selections and combinations of parameters through the use of user screens to understand the interaction of various parameters and their impact on weld quality with proper terminology and visual elements related to automated welding. 
     By implementing welding (e.g., orbital GTAW) training in a simulated environment, a number of issues may be addressed. For example, industry and experience in the welding process may be based on the knowledge of the development company and therefore is consistent and updated to the latest technology and standards available, which is easily done by software upgrade in a virtual environment. The instructor becomes a facilitator to the program and does not need to be an expert in the welding process. Additional training aids, such as path following cues or visual overlays, improve transfer of training in a virtual environment. Welding equipment, that can become outdated, does not need to be purchased. The virtual reality welding system can be used in a one-on-one training environment or a classroom type of setting. 
     The use of a virtual framework allows multiple pendants to be simulated with one training device. In implementing a welding (e.g., orbital GTAW) process in virtual reality, a pendant can be made as a physical device or as a virtual pendant. With the physical device, the student is able to interact with the controls and get the “feel” for the control. With a virtual pendant, where the controls are available and interacted with on a touch screen, the user can easily choose a variety of pendants for control, whether they are customized or company dependent. A virtual pendant also allows for different types of controls or levels to be enabled for use by the student depending on learning levels or controls available based on their industry level (mirroring field work experience). Unlike traditional training, randomized faults (e.g., wire nesting) can be implemented that provide the user a more detailed and complete experience without damage to the equipment or time-consuming setup. 
     Part of the learning interaction is the understanding of proper welding parameters based on the joint, preparation, material type, etc. In accordance with an exemplary embodiment, in virtual reality, theory enabled screens can be enabled to prompt a user with knowledge as to the proper choice to make. Additional screens or tables can be enabled to prompt a user with knowledge of what to input, but can also be enabled when a wrong choice is selected to highlight what was chosen and why it was incorrect, with the proper selections identified. This type of intelligent agent can ensure that the student does not perform incorrectly and become frustrated by the end result, positive reinforcement and learning being the key. An exemplary embodiment of the invention will also allow for the system or instructor to quiz the user&#39;s knowledge and adapt the training curriculum and testing to the individual user&#39;s blind spots. An exemplary embodiment of the invention employs artificial intelligence (AI) and a learning management system (LMS) to help with instruction in needed areas, reinforce knowledge, and provide learning assistance. 
     Setup parameters may include, but are not limited to: inert gas (e.g., Argon, Helium); arc ignition; welding current (e.g., pulsed vs. unpulsed); downslope functionality to avoid crate ring at the end of the weld; torch rotation travel speed; wire feed characteristics (e.g., pulsed waveforms); wire diameter selection; arc voltage; distance between electrode and work piece; welding oscillation control; remote control; cooling characteristics of the generally integrated closed-loop water cooling circuit; and weld cycle programming (often with four axes), etc. 
     Inspection and review of the weld is another aspect to the learning process. The student can view the weld and identify what is correct or wrong and, based on these choices, receive a score to identify whether they were right and further receive input on what is right or wrong based on industry standards. This can be enhanced further to identify how to correct these situations. For instance, with the correct amperage and speed (identified), the weld may be a good weld based on a particular industry standard. 
     As described above, a physical teach pendant or a hand-held control device for input selection in virtual reality welding may be provided. Alternatively, a virtual teach pendant device for control input selection for simulated welding may be provided. Interactions with the handheld or virtual device that are student learning level or industry role dependent can be enabled on the device. Restricting controls or interactions based on the user may be provided to enhance learning objectives or reinforce industry role interactions, in accordance with an exemplary embodiment. 
     Teaching interaction or reactions based on visual, audible, or physical changes may be provided to ensure the user knows the proper set-up or error recovery. Also, teaching interaction or reactions based on visual, audible, or physical changes may be provided to ensure the user knows the proper changes in controls needed based on environmental or weld specific changes being made. Virtual calculators or tables may be enabled that allow input and provide an output based on values entered. Intelligent agent enabled results based on incorrect set-up parameters or choices may be provided to reinforce correct industry standards. Furthermore, intelligent agent enabled input to identify what the proper controls input should have been may be provided, based on the current visual, audio, or physical indicators. In accordance with an exemplary embodiment, the simulation of camera based systems may be provided along with the creation of path following and path determinative systems based upon a fuzzy logic controller based system. For example, multiple renderings may be provided by simulating two camera views such that the camera views may be moved during the simulation. In accordance with an exemplary embodiment, an alarm may sound when the desired path is deviated from, based on the fuzzy logic, for example. Visualization of a simulated TIG weld puddle may be provided via pixel sizes that are small enough to provide proper visualization of the TIG weld puddle. Simulation of the magnification of the simulated TIG weld puddle may also be provided, for better visualization by the user. 
     Multiple levels of experience for the user that adapt to the skill level, learning pace, and learning style of the user (LMS compatible) may be provided. Artificial intelligence (AI) based fault induction may also be provided in order to test the user&#39;s ability to detect, correct, and recover from problems. The simulation of unsafe conditions, machine setup, and materials defects may be provided. Also, a multi-language capable system may be provided, allowing for harmonization of training for a global marketplace, in accordance with an exemplary embodiment. An exemplary embodiment of the invention may provide a virtual reality environment allowing two or more users (multi-man) to create a virtual weld at the same time. In some exemplary embodiments of the invention, the welds of the separate users may be joined by one or more tie-in operations. 
     In summary, disclosed is a real-time welding simulator including a programmable processor-based subsystem, a spatial tracker operatively connected to the programmable processor-based subsystem, at least one mock welding tool capable of being spatially tracked by the spatial tracker, and at least one display device operatively connected to the programmable processor-based subsystem. The simulator is capable of simulating, in virtual reality space, a weld puddle having real-time molten metal fluidity and heat dissipation characteristics. The simulator is further capable of displaying the simulated weld puddle on the display device in real time. 
     The invention has been described herein with reference to various disclosed exemplary embodiments. Obviously, modifications and alterations will occur to others upon a reading and understanding of this specification. It is, therefore, intended to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalence thereof.