Patent Publication Number: US-9836994-B2

Title: Virtual welding system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 13/364,489, filed on Feb. 2, 2012 which application is a continuation-in-part of U.S. patent application Ser. No. 12/501,257 (U.S. Pat. No. 8,747,116), filed on Jul. 10, 2009. 
    
    
     BACKGROUND 
     Technical Field 
     The present disclosure is related to virtual reality simulation and, more particularly, to systems and methods for providing arc welding training in a simulated virtual reality environment or augmented reality environment. 
     Discussion of Art 
     Learning how to arc weld traditionally takes many hours of instruction, training, and practice. There are many different types of arc welding and arc welding processes that can be learned. Typically, welding is learned by a student using a real welding system and performing welding operations on real metal pieces. Such real-world training can tie up scarce welding resources and use up limited welding materials. Recently, however, the idea of training using welding simulations has become more popular. Some welding simulations are implemented via personal computers and/or on-line via the Internet. Current known welding simulations, however, tend to be limited in their training focus. 
     For example, some welding simulations focus on training only for “muscle memory”, which simply trains a welding student how to hold and position a welding tool. Other welding simulations focus on showing visual and audio effects of the welding process, but only in a limited and often unrealistic manner which does not provide the student with the desired feedback that is highly representative of real world welding. It is this actual feedback that directs the student to make necessary adjustments to make a good weld. Welding is learned by watching the arc and/or puddle, not solely by muscle memory. 
     Further limitations and disadvantages of conventional, traditional, and previously proposed approaches will become apparent to one of skill in the art, through comparison of such approaches with embodiments of the present invention as set forth in the remainder of the present application with reference to the drawings. 
     BRIEF DESCRIPTION 
     In one aspect of the invention, a virtual welding system includes a programmable processor based subsystem and a spatial tracker operatively connected to the programmable processor based subsystem. A mock welding tool is employed, which is capable of being spatially tracked by the spatial tracker. The mock welding tool includes one or more adapters, wherein each adapter emulates the real-world appearance of a particular weld type. A base is removably coupled to each of the one or more adapters. 
     In another aspect of the invention, a mock welding tool is used within a virtual welding system. One or more adapters are employed, wherein each adapter emulates the physical characteristics of a particular weld type. A base is removably coupled to each of the one or more adapters, the base identifies a real time spatial location of the mock welding tool relative to a datum location. 
     Further, a method is employed to use a mock welding tool within a virtual welding system. A first adapter is removably connected to a base, the first adapter being associated with a first weld type. The first adapter is removed from the base wherein a second adapter is removably connected to the base, the second adapter being associated with a second weld type. The use of a plurality of adapter types with a common base facilitates use of a portable virtual welding system that can be employed in substantially any mobile location. 
     This brief description is provided to introduce a selection of concepts in a simplified form that are further described herein. This brief description is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference is made to the accompanying drawings in which particular embodiments and further benefits of the invention are illustrated as described in more detail in the description below, in which: 
         FIG. 1  is a block diagram of a virtual welding system that includes an interchangeable mock welding tool with a base that can connect to each of a plurality of adapters; 
         FIG. 2  is one implementation of the system set forth in  FIG. 1 ; 
         FIG. 3  is an exemplary side plan view of a GMAW adapter that removably couples to a base; 
         FIG. 4  is an exemplary perspective view of a stick tool adapter that removably couples to a base; 
         FIG. 5  is an exemplary perspective view of an oxyfuel adapter that removably couples to a base; 
         FIG. 6  is a perspective view of a base that can interface with the adapters set forth in  FIGS. 3, 4 and 5 ; 
         FIG. 7  is a cut-away perspective view of the base depicted in  FIG. 6 ; 
         FIG. 8A  is a perspective view of an assembled mock welding tool that includes the base and a stick tool adapter; 
         FIG. 8B  is a perspective view of an exploded mock welding tool that includes the base and a stick tool adapter; 
         FIG. 9  is a perspective view of a stand utilized to hold a welding coupon and magnet in known spatial locations; 
         FIG. 10  is a perspective view illustrating the stand of  FIG. 9  in an alternate, compactable position to hold the welding coupon and magnet in known spatial locations; 
         FIG. 11  is an assembly view illustrating a kit that includes components to transport and operate a mobile virtual welding system; 
         FIG. 12  is a front elevational view illustrating a user interface to communicate with a virtual welding system; 
         FIG. 13  is a front elevational view illustrating an alternate user interface to communicate with a virtual welding system; 
         FIG. 14  is a perspective view of a helmet that can be used by a user within a virtual welding system; 
         FIG. 15  is a rear perspective view of an FMDD mounted within a welding helmet that is used within a virtual welding system; 
         FIG. 16  is a flow diagram of an example embodiment of a subsystem block diagram of a programmable processor-based subsystem (PPS) shown in  FIG. 1 ; 
         FIG. 17  is a flow diagram of an example embodiment of a block diagram of a graphics processing unit of the PPS of  FIG. 16 ; 
         FIG. 18  is a flow diagram of an example embodiment of a functional block diagram of the system of  FIG. 1 ; 
         FIG. 19  is a flowchart of an embodiment of a method of training using the virtual reality training system of  FIG. 1 ; 
         FIG. 20  is an elevation view showing a welding pixel (wexel) displacement map, in accordance with an embodiment of the present invention; 
         FIG. 21  is a perspective view of a coupon space and corresponding x-y weld space plot of a flat welding coupon simulated in the system of  FIG. 1 ; 
         FIG. 22  is a perspective view of a corner and corresponding T-S weld space plot of a corner (tee joint) welding coupon simulated in the system of  FIG. 1 ; 
         FIG. 23  is a perspective view of a pipe coupon and corresponding T-S weld space plot of a pipe welding coupon simulated in the system of  FIG. 1 ; and 
         FIGS. 24A-24C  are elevation views illustrating the concept of a dual displacement puddle of the system of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the figures, several embodiments or implementations of the present invention are hereinafter described in conjunction with the drawings, wherein like reference numerals are used to refer to like elements throughout. The present embodiments are directed to a virtual welding system that employs a mock welding tool that has a base to accommodate a plurality of adapters, wherein each adapter simulates a different weld type. The adapters can be have a common size to allow seamless removable coupling with the base when desired. Although illustrated and described hereinafter in the context of various exemplary virtual welding systems, the invention is not limited to the illustrated examples. 
     More particularly, the subject embodiments relate to a virtual reality welding system that includes 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. To provide additional flexibility, the mock welding tool includes a base and a plurality of adapters, wherein each adapter is used to simulate a different welding type. For example, a first adapter can simulate GMAW welding, a second adapter can simulate SMAW welding, a third adapter can simulate oxyfuel welding, and so on. Alternatively or in addition, the tools can be used to simulate a cutting device, such as an oxyfuel or other cutting torch. The adapters can all have a standardized size to allow seamless switching as they are removed and connected to a common base. In order to accommodate portable use, a compactable stand is employed to hold a welding coupon in space for use with the mock welding tool. In this manner, the system is capable of simulating a plurality of weld types in virtual reality space, wherein a weld puddle has real-time molten metal fluidity and heat dissipation characteristics that are commensurate with each weld type. 
     The real-time molten metal fluidity and heat dissipation characteristics of the simulated weld puddle provide real-time visual feedback to a user of the mock welding tool when displayed, allowing the user to adjust or maintain a welding technique in real-time in response to the real-time visual feedback. The displayed weld puddle is representative of a weld puddle that would be formed in the real-world based on the user&#39;s welding technique and the selected welding process and parameters. By viewing a puddle (e.g., shape, color, slag, size), a user can modify his technique to make a good weld and determine the type of welding being done. The shape of the puddle is responsive to the movement of the mock welding tool. As used herein, the term “real-time” means perceiving and experiencing in time in a simulated environment in the same way that a user would perceive and experience in a real-world welding scenario. Furthermore, the weld puddle is responsive to the effects of the physical environment including gravity, allowing a user to realistically practice welding in various positions including horizontal, vertical, and overhead welding and various pipe welding angles. 
     Referring now to the drawings wherein the showings are for the purpose of illustrating the exemplary embodiments,  FIG. 1  is a block diagram of a virtual welding system  100  that provides arc welding training in a real-time virtual reality environment. The virtual welding system  100  includes a programmable processor-based subsystem (PPS)  110 . The virtual welding system  100  further includes a spatial tracker (ST)  120  operatively connected to the PPS  110 . The virtual welding system  100  also includes a physical welding user interface (WUI)  130  operatively connected to the PPS  110  and a face-mounted display device (FMDD)  140  operatively connected to the PPS  110  and the ST  120 . The virtual welding system  100  further includes an observer display device (ODD)  150  operatively connected to the PPS  110 . The virtual welding system  100  also includes at least one mock welding tool (MWT)  160  operatively connected to the ST  120  and the PPS  110 . The virtual welding system  100  further includes a stand  170  and at least one welding coupon (WC)  180  capable of being attached to the stand  170 . The MWT  160  can include a base (not shown) that couples to one or more adapters (not shown) to simulate a plurality of different weld types. 
       FIG. 2  illustrates a system  200  that illustrates one implementation of the system set forth in  FIG. 1 . The FMDD  140  is used to display a simulated virtual environment for a user to visually experience welding. In order to provide an accurate rendering of this simulated environment, the FMDD  140  is communication with the PPS  110  to receive and transmit data relative to the spatial location of the FMDD  140  in the system  200 . Communication can be facilitated utilizing known hardwire and/or wireless technologies including Bluetooth, wireless Ethernet and the like. To acquire spatial location data, one or more sensors  142  are disposed within and/or proximate to FMDD  140 . The sensors  142 , in turn, evaluate spatial location relative to a particular datum within the system  200 , such as a magnet  172 . The magnet  172  can be located at a known datum point and disposed a predetermined distance  178  relative to the welding coupon  180 . This predetermined distance  178  can be maintained by utilizing a form factor, template, or preconfigured structure in association with the stand  170 . Thus, movement of the sensors  142  relative to the magnet  172  can inherently provide location data of the FMDD  140  relative to the welding coupon  180  within the stand  170 . The sensors  142  can communicate wirelessly to identify location relative to the magnet utilizing known communication protocols to update the FMDD  140  in real-time to coincide with the user&#39;s motion. 
     The system  200  also includes the MWT  160 , which includes an adapter  162  that is coupled to a base  166 . It is to be appreciated that the adapter  162  is merely representative of one of a plurality of adapters that each simulate a particular weld type. The adapter  162  is removably coupled to the base  166  to allow removal and replacement of one adapter as a substitute for another. Removable coupling can be accomplished utilizing tabs, dimples, sliders, push buttons, etc. to allow a user to depress, twist, or otherwise mechanically modify the adapter  162  and/or the base  166 . In order to accurately simulate the particular weld type, each adapter  162  is sized to represent a real world equivalent that would be used to perform actual weld operations. Once a particular adapter is coupled to the base, the user can input the type of adapter in use, to allow the PPS to load and execute an appropriate instruction set associated therewith. In this manner, an accurate rendering is displayed on the FMDD  140  that is commensurate with each adapter type. 
     One or more sensors  168  can be disposed within or proximate to the base  166 . As with the FMDD  140 , the sensors  168  can wirelessly determine spatial location relative to the magnet  172  on the stand  170 . In this manner, the adapter  162  and base  166 , in combination, inherently have a known location and space relative to the magnet  172  as the dimensions of both the adapter  162  and the base  166  are predetermined. In order to insure that the system  200  is calibrated properly to accommodate each adapter  162 , a user may interface with the PPS  110  (e.g. via the WUI  130 ) to indicate that a particular adapter is currently in use. Once such an indication is made, the PPS  110  can retrieve a lookup table from the memory  112 , which contains a rule set to properly render a simulated environment as experienced by the user through the FMDD  140 . 
     In an embodiment, the PPS  110  is a computer operable to execute the disclosed architecture. In order to provide additional context for various aspects of the present invention, the following discussion is intended to provide a brief, general description of a suitable computing environment in which the various aspects of the present invention may be implemented. The PPS  110  can employ computer-executable instructions that may run on one or more computers, implemented in combination with other program modules, and/or as a combination of hardware and software. Generally, program modules include routines, programs, components, data structures, etc., that perform particular tasks or implement particular abstract data types. For example, such programs and computer-executable instructions can be processed via a robot using various machine control paradigms. 
     Moreover, those skilled in the art will appreciate that the inventive methods may be practiced with other computer system configurations, including single-processor or multiprocessor computer systems, minicomputers, mainframe computers, as well as personal computers, hand-held computing devices, microprocessor-based or programmable consumer electronics, and the like, each of which may be operatively coupled to one or more associated devices. The illustrated aspects of the invention may also be practiced in distributed computing environments where certain tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote memory storage devices. 
     The PPS  110  can utilize an exemplary environment for implementing various aspects of the invention including a computer, wherein the computer includes a processor  114 , a memory  112  and a system bus for communication purposes. The system bus couples system components including, but not limited to the memory  112  to the processor  114 . The processor  114  may be any of various commercially available processors. Dual microprocessors and other multi-processor architectures also can be employed as the processor  114 . 
     The system bus can be any of several types of bus structure including a memory bus or memory controller, a peripheral bus and a local bus using any of a variety of commercially available bus architectures. The memory  112  can include read only memory (ROM) and random access memory (RAM). A basic input/output system (BIOS), containing the basic routines that help to transfer information between elements within the PPS  110 , such as during start-up, is stored in the ROM. 
     The PPS  110  can further include a hard disk drive, a magnetic disk drive, e.g., to read from or write to a removable disk, and an optical disk drive, e.g., for reading a CD-ROM disk or to read from or write to other optical media. The PPS  110  can include at least some form of computer readable media. Computer readable media can be any available media that can be accessed by the computer. By way of example, and not limitation, computer readable media may comprise computer storage media and communication media. Computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by the PPS  110 . 
     Communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared and other wireless media. Combinations of any of the above should also be included within the scope of computer readable media. 
     A number of program modules may be stored in the drives and RAM, including an operating system, one or more application programs, other program modules, and program data. The operating system in the PPS  110  can be any of a number of commercially available operating systems. 
     In addition, a user may enter commands and information into the computer through a keyboard and a pointing device, such as a mouse. Other input devices may include a microphone, an IR remote control, a track ball, a pen input device, a joystick, a game pad, a digitizing tablet, a satellite dish, a scanner, or the like. These and other input devices are often connected to the processor through a serial port interface that is coupled to the system bus, but may be connected by other interfaces, such as a parallel port, a game port, a universal serial bus (“USB”), an IR interface, and/or various wireless technologies. A monitor (not shown) or other type of display device, may also be connected to the system bus via an interface, such as a video adapter. Visual output may also be accomplished through a remote display network protocol such as Remote Desktop Protocol, VNC, X-Window System, etc. In addition to visual output, a computer typically includes other peripheral output devices, such as speakers, printers, etc. 
     A display, such as the ODD  150  and the WUI  130 , can be employed with the PPS  110  to present data that is electronically received from the processor. For example, the display can be an LCD, plasma, CRT, etc. monitor that presents data electronically. Alternatively or in addition, the display can present received data in a hard copy format such as a printer, facsimile, plotter etc. The display can present data in any color and can receive data from the PPS  110  via any wireless or hard wire protocol and/or standard. In an embodiment, the WUI  130  is a touch-screen that allows a user to interface with the PPS  110  such as reviewing weld data from one or more previous simulations. A user can also navigate through various data paradigms to identify information relevant to a particular analysis (e.g., weld quality), wherein such data is evaluated against one or more benchmarks for scoring or other comparison. 
     The computer can operate in a networked environment using logical and/or physical connections to one or more remote computers, such as a remote computer(s). The remote computer(s) can be a workstation, a server computer, a router, a personal computer, microprocessor based entertainment appliance, a peer device or other common network node, and typically includes many or all of the elements described relative to the computer. The logical connections depicted include a local area network (LAN) and a wide area network (WAN). Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets and the Internet. 
     When used in a LAN networking environment, the computer is connected to the local network through a network interface or adapter. When used in a WAN networking environment, the computer typically includes a modem, or is connected to a communications server on the LAN, or has other means for establishing communications over the WAN, such as the Internet. In a networked environment, program modules depicted relative to the computer, or portions thereof, may be stored in the remote memory storage device. It will be appreciated that network connections described herein are exemplary and other means of establishing a communications link between the computers may be used. 
       FIGS. 3-5  illustrate non-limiting example embodiments of the adapter  162 , wherein  FIG. 3  shows the adapter  162  as a GMAW welding gun  300 ;  FIG. 4  shows the adapter  162  as a stick welding tool  400 ; and  FIG. 5  shows the adapter  162  as an oxyfuel torch  500 . Although, the adapters are described herein as having a plurality of different components, it is to be appreciated that both unitary and multi-component embodiments of the adapter are contemplated within the scope of this invention. Turning first to  FIG. 3 , the GMAW welding gun  300  includes a nozzle  310  connected to an interface  318  via a tube  312 . The welding gun  300  can have substantially the same weight and dimension as a GMAW gun as used in real-world applications. The dimension of each component within the gun  300  can be a known value, which can be used to calibrate the gun in view of the welding coupon  180  and magnet  172 . The interface  318  can include one or more mechanical features to allow removable coupling of the adapter  300  to a base. 
       FIG. 4  illustrates the stick welding tool  400  for plate and pipe welding and includes a holder  422  and a simulated stick electrode  410 . In an embodiment, the simulated stick electrode  410  can include a tactilely resistive tip to simulate resistive feedback that occurs during, for example, a root pass welding procedure in real-world pipe welding or when welding a plate. If the user moves the simulated stick electrode  162  too far back out of the root, the user will be able to feel or sense the lower resistance, thereby deriving feedback for use in adjusting or maintaining the current welding process. An interface  418  allows removable coupling of the stick welding tool  400  to a base. 
       FIG. 5  illustrates the oxyfuel adapter  500  that includes a nozzle  510  and an interface  518  that allows removable coupling of the oxyfuel adapter  500  to a base. In this embodiment, the interface  518  includes a collar  522  that can be secured around the diameter of the base. A push button  520  can include a protrusion or other feature to mechanically interface with a complimentary feature (e.g., dimple) on the base. In this manner, the adapter  500  can “lock” to the base dependent upon whether the push button is depressed or otherwise manipulated. In other embodiments, the oxyfuel adapter can be used to represent and cutting torch that is used to cut metal objects. In this embodiment, the cutting torch is displayed within the virtual weld system as it would operate in a real-world application. For example, the PPS  110  can load and execute code that is representative of a cutting torch application instead of a welding torch. 
     Other mock welding tools are possible as well, in accordance with other embodiments of the present invention, including a MWT that simulates a hand-held semi-automatic welding gun having a wire electrode fed through the gun, for example. Furthermore, in accordance with other certain embodiments of the present invention, a real welding tool could be used as the MWT  160  to better simulate the actual feel of the tool in the user&#39;s hands, even though, in the virtual welding system  100 , the tool would not be used to actually create a real arc. Also, a simulated grinding tool may be provided, for use in a simulated grinding mode of the virtual welding system  100 . Similarly, a simulated cutting tool may be provided, for use in a simulated cutting mode of the virtual welding system  100 . Furthermore, a simulated gas tungsten arc welding (GTAW) torch or filler material may be provided for use in the virtual welding system  100 . 
       FIG. 6  illustrates a base  600  that is employed to interface to one or more adapters such as the GMAW gun  300 , the stick-welding tool  400 , and the oxyfuel adapter  500 . The base  600  includes a body  620 , which can house one or more electronic components, such as the sensors  168  described herein. In an embodiment, the body  620  is comprised of two halves that are held together via fasteners  640  such as, for example, screws, bolts, rivets, etc. A hard-wire cable  630  extends from the body  620  to facilitate communication of the base  600  with the PPS  110 . 
     The interface  610  includes a landing  614  and a dimple  616  disposed therein on opposite sides of the interface  610 . The landing and dimple combination can serve as a removable interlock for a complimentary component within the interface of the exemplary adapters  300 ,  400 ,  500 . Substantially any mechanical interface, however, is contemplated to facilitate efficient removal and replacement of an adapter to the base  600 . A push button  618  disposed within a protrusion  636  can be employed to indicate that a user is in an active welding mode when the push button  618  is depressed. With at least reference to the adapter  400 , a complimentary form factor can be included in the adapter to fit as a sleeve over the push button  618  wherein the user can depress the push button via a form factor feature on the adapter. For this purpose, the adapter form factor can simulate a real world trigger or a similar device to give the user a real world look and feel for weld operation. 
       FIG. 7  is a cut-away perspective view of the base  600  to reveal a sensor  652  disposed therein. The sensor  652  communicates with one or more different components (e.g., PPS  110 ) via a cable  654  and is disposed within the base  600  in a pre-determined location and held in place via fasteners  658 . Vanes  672  provides structural support for the base  600  throughout the body  620 . In an embodiment, the sensor  652  utilizes known non-contact technology such as capacitance sensors, piezoelectric, eddy current, inductive, ultrasonic, Hall effect, and/or infrared proximity sensor technologies. Such technologies can be used with other sensors described herein including sensors  142  and  168  used in the helmet  146  and base  166  respectively.  FIG. 8  illustrates a mock welding tool  800  wherein the adapter  400  is removably coupled to the base  600  for use within the virtual welding system  100 . 
       FIG. 9  illustrates a stand  700  that is utilized to locate a welding coupon  758  in space at a known location relative to a magnet  710 . The stand  700  includes an arm  714  and a base  724  which are coupled together via an upright  722 . In an embodiment, the upright  722  is removably engaged to the base  724  to allow the stand  700  to be broken down into individual components for packaging and shipping. In addition, the base  724  and upright  722  can have one or more structural features (e.g., vanes) that add structural support to such components that at the same time maintain a relatively low weight. A plunger  732  can be drawn away from the arm  714  to allow the removal and replacement of coupons onto the stand  700  in a repeatable spatial location. 
     The dimensions of the arm  714  and the location of the welding coupon  758  relative to a magnet  710  disposed on a landing  738  are all known, a mock welding tool proximate to the welding coupon  758  will have a known and repeatable output thereby providing an appropriate real-time virtual welding environment to the user. Pins  762 ,  764  can be removed from the stand  700  to allow the arm  714  to pivot around the pin  764  as depicted in  FIG. 10 . In this embodiment, the pin  762  is removed from hole  766 ,  768  thereby allowing the arm  714  to rotate around the pin  764  to a second location. In this manner, a user can simulate welds in a multiple number of planes (e.g., horizontal and vertical) to learn the nuances associated with each. It is worth noting that the design of the stand  700  insures that the spatial location of the magnet  710  relative to the welding coupon  758  is maintained in either position to provide accurate and repeatable results for creation and display of the real-time welding environment simulation. 
       FIG. 11  illustrates a portable welding kit that can be easily transported from location to location. The kit can be set up in substantially any location proximate to a power source, which may include a battery, A/C, or other power. A container  810  can be substantially shaped as a welding machine housing wherein the interior includes a plurality of shells, platforms and other storage areas to accommodate the WUI  130 , the stand  700 , the mock welding tool  800 , and a helmet  900 . The container can further include wheels to facilitate efficient transport of the container  810 . 
       FIG. 12  illustrates an exemplary user interface  830  that displays a plurality of metrics associated with a typical weld system. The interface  830  includes a selector  832  to identify the type of adapter utilized with the simulated weld system. A temperature gauge  836 , a current gauge  838 , and a voltage gauge  842  can provide real-time feedback to a user during weld operation. Similarly,  854  and  856  display additional information and allow user input to modify the same.  FIG. 13  shows an alternate user interface  860  that simulates a real world hardware weld system interface. In an embodiment, a user is able to provide input to the display  860  using a touch screen or other peripheral input method as described herein. 
       FIGS. 14 and 15  illustrate a helmet  900  that is worn by the user when operating the virtual welding system.  FIG. 14  shows a front perspective view of the helmet  900 , which can be an actual welding helmet used in real-world application and retrofitted to include the FMDD, as described above. In this manner, a user can wear a welding helmet just as they would in a real world scenario wherein the virtual environment is displayed to the user in real-time via the FMDD  140 .  FIG. 15  illustrates an example embodiment of the FMDD  140  of integrated into a welding helmet  900 . The FMDD  140  operatively connects to the PPS  110  and the ST  120  either via wired means or wirelessly. A sensor  142  of the ST  120  may be attached to the FMDD  140  or to the welding helmet  900 , in accordance with various embodiments of the present invention, allowing the FMDD  140  and/or welding helmet  900  to be tracked with respect to the 3D spatial frame of reference created by the ST  120 . 
       FIG. 16  illustrates an example embodiment of a subsystem block diagram of the programmable processor-based subsystem (PPS)  110  of the virtual welding system  100  of  FIG. 1 . The PPS  110  includes a central processing unit (CPU)  111  and one or more graphics processing units (GPU)  115 , in accordance with an embodiment of the present invention. In one embodiment, one GPU  115  is used to provide monoscopic vision on the FMDD  140 . In another embodiment, two GPUs  115  are programmed to provide stereoscopic vision on the FMDD  140 . In either case, a user views a virtual reality simulation of a weld puddle (a.k.a. a weld pool) having real-time molten metal fluidity and heat absorption and dissipation characteristics, in accordance with an embodiment of the present invention. 
       FIG. 17  illustrates an example embodiment of a block diagram of a graphics processing unit (GPU)  115  of the PPS  110  of  FIG. 10 . Each GPU  115  supports the implementation of data parallel algorithms. In accordance with an embodiment of the present 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 FMDD  140 , rendering the welder&#39;s point of view, and a third video output may be routed to the ODD  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. Both GPUs  115  perform the same welding physics computations but may render the virtual reality environment from the same or different points of view. The GPU  115  includes a compute 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 . 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 embodiment of the present invention, the physics model runs and updates at a rate of about 30 times per second. 
       FIG. 18  illustrates an example embodiment of a functional block diagram of the virtual welding system  100  of  FIG. 1 . The various functional blocks of the virtual welding system  100  as shown in  FIG. 12  are implemented largely via software instructions and modules running on the PPS  110 . The various functional blocks of the virtual welding system  100  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 , welding 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 spatial effects  1222 . 
     The internal architecture functionality  1207  provides the higher level software logistics of the processes of the virtual welding system  100  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 embodiment of the present invention. Certain real-time inputs to the PPS  110  include arc location, gun position, FMDD or helmet position, gun on/off state, and contact made state (yes/no). 
     The graphical user interface functionality  1213  allows a user, through the ODD  150  using the joystick  132  of the physical user interface  130 , to set up a welding scenario. In accordance with an embodiment of the present invention, the set up of a welding scenario includes selecting a language, entering a user name, selecting a practice plate (i.e., a welding coupon), selecting a welding process (e.g., FCAW, GMAW, SMAW) and associated axial spray, pulse, or short arc methods, selecting a gas type and flow rate, selecting a type of stick electrode (e.g.,  6010  or  7018 ), and selecting a type of flux cored wire (e.g., self-shielded, gas-shielded). The set up of a welding scenario also includes selecting a table height, an arm height, an arm position, and an arm rotation of the stand  170 . 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, setting an amperage, selecting a polarity, and turning particular visual cues on or off. 
     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 ODD  150 ). Tracking information from the ST  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 distance 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. For each parameter analyzed by the SAM and the WWAM, 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 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 improper weld size, poor bead placement, concave bead, excessive convexity, undercut, porosity, incomplete fusion, slag entrapment, overfill, burnthrough, and excessive spatter. In accordance with an embodiment of the present 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. The optimum values are derived from real-world data. 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. 
     The virtual welding system  100  is capable of analyzing and displaying the results of virtual welding activity. By analyzing the results, it is meant that virtual welding system  100  is capable of determining when during the welding pass and where along the weld joints, the user deviated from the acceptable limits of the welding process. A score may be attributed to the user&#39;s 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 virtual welding system  100  as chosen for scoring the user&#39;s performance. Scoring may be displayed numerically or alpha-numerically. Additionally, the user&#39;s 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. The tolerance ranges of the parameters are taken from real-world welding data, thereby providing accurate feedback as to how the user will perform in the real world. In another embodiment, analysis of the defects corresponding to the user&#39;s performance may also be incorporated and displayed on the ODD  150 . 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 ODD  150 , defects may still have occurred as a result of the user&#39;s performance, the results of which may still be correspondingly displayed, i.e. graphed. 
     Visual cues functionality  1219  provide immediate feedback to the user by displaying overlaid colors and indicators on the FMDD  140  and/or the ODD  150 . Visual cues are provided for each of the welding parameters  151  including position, tip to work distance, weld angle, travel angle, travel speed, and arc length (e.g., for stick welding) 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 and weld bead “dime” spacing, for example. Visual cues may be set independently or in any desired combination. 
     Calibration functionality  1208  provides the capability to match up physical components in real world space (3D frame of reference) with visual components in virtual reality space. Each different type of welding coupon (WC) is calibrated in the factory by mounting the WC to the arm  714  of the stand  170  and touching the WC at predefined points (indicated by, for example, three dimples on the WC) with a calibration stylus operatively connected to the ST  120 . The ST  120  reads the magnetic field intensities at the predefined points, provides position information to the PPS  110 , and the PPS  110  uses the position information to perform the calibration (i.e., the translation from real world space to virtual reality space). 
     Any particular type of WC fits into the arm  714  of the stand  170  in the same repeatable way to within very tight tolerances. In one example, the distance between the coupon  758  and the magnet  710  on the arm  714  is a known distance  178  as set forth in  FIG. 2  above. Therefore, once a particular WC type is calibrated, that WC type does not have to be re-calibrated (i.e., calibration of a particular type of WC is a one-time event). WCs 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 MWT  160  around the corner of an actual WC  180 , the user will see the tip sliding around the corner of the virtual WC on the FMDD  140  as the user feels the tip sliding around the actual corner. In accordance with an embodiment of the present invention, the MWT  160  is placed in a pre-positioned jig and is calibrated as well, based on the known jig position. 
     In accordance with an alternative embodiment of the present invention, “smart” coupons are provided, having sensors on, for example, the corners of the coupons. The ST  120  is able to track the corners of a “smart” welding coupon such that the virtual welding system  100  continuously knows where the “smart” welding coupon is in real world 3D space. In accordance with a further alternative embodiment of the present invention, licensing keys are provided to “unlock” welding coupons. When a particular WC is purchased, a licensing key is provided allowing the user to enter the licensing key into the virtual welding system  100 , unlocking the software associated with that WC. In accordance with another embodiment of the present invention, spatial non-standard welding coupons may be provided based on real-world CAD drawings of parts. Users may be able to train on welding a CAD part even before the part is actually produced in the real world. 
     Sound content functionality  1204  and welding sounds  1205  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 MWT  160  positioned correctly, and a hissing sound is provided when the MWT  160  is positioned correctly. In a short arc welding process, a steady crackling or frying sound is provided for proper welding technique, and a hissing sound may be provided when undercutting is occurring. These sounds mimic real world sounds corresponding to correct and incorrect welding technique. 
     High fidelity sound content may be taken from real world recordings of actual welding using a variety of electronic and mechanical means, in accordance with various embodiments of the present invention. In accordance with an embodiment of the present invention, the perceived volume and directionality of sound is modified depending on the position, orientation, and distance of the user&#39;s head (assuming the user is wearing a FMDD  140  that is tracked by the ST  120 ) with respect to the simulated arc between the MWT  160  and the WC  180 . Sound may be provided to the user via ear bud speakers in the helmet  900  or via speakers configured in the console  135  or stand  170 , for example. 
     Environment models  1203  are provided to provide various background scenes (still and moving) in virtual reality space. Such background environments may include, for example, an indoor welding shop, an outdoor race track, a garage, etc. and may include moving cars, people, birds, clouds, and various environmental sounds. The background environment may be interactive, in accordance with an embodiment of the present invention. For example, a user may have to survey a background area, before starting welding, to ensure that the environment is appropriate (e.g., safe) for welding. Torch and clamp models  1202  are provided which model various MWTs  160  including, for example, guns, holders with stick electrodes, etc. in virtual reality space. 
     Coupon models  1210  are provided which model various WCs  180  including, for example, flat plate coupons, T-joint coupons, butt-joint coupons, groove-weld coupons, and pipe coupons (e.g., 2-inch diameter pipe and 6-inch diameter pipe) in virtual reality space. Alternatively or in addition, welding coupon models can include multi-versions, wherein the coupons include one or more welding coupon types within a single form factor. For example, an exemplary multi-welding coupon may include a T-joint, butt-joint, and groove-weld in a single component. A stand/table model  1206  is provided which models the various parts of the stand  700  including an adjustable arm  714 , a base  724 , and an upright  174  used to couple the adjustable arm to the base as used in virtual reality space. A physical interface model  1201  is provided which models the various parts of the welding user interface  130 , console  135 , and ODD  150  in virtual reality space. 
     In accordance with an embodiment of the present 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 is run on the GPUs  115 , in accordance with an embodiment of the present 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. 24A-24C . 
     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. For example, slag may be shown rendered over a weld bead during and just after a welding process, and then removed to reveal the underlying weld bead. The renderer functionality  1216  is used to render various non-puddle specific characteristics using information from the spatial effects module  1222  including sparks, spatter; smoke, arc glow, fumes and gases, 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 embodiment of the present 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. 19  is a flow chart of an embodiment of a method  1300  of training using the virtual welding system  100  of  FIG. 1 . In step  1310 , move a mock welding tool with respect to a welding coupon in accordance with a welding technique. In step  1320 , track position and orientation of the mock welding tool in three-dimensional space using a virtual reality system. In step  1330 , view a display of the virtual reality welding system showing a real-time virtual reality simulation of the mock welding tool and the welding coupon in a virtual reality space 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 , view on the display, real-time molten metal fluidity and heat dissipation characteristics of the simulated weld puddle. In step  1350 , modify in real-time, at least one aspect of the welding technique in response to viewing the real-time molten metal fluidity and heat dissipation characteristics of the simulated weld puddle. 
     The method  1300  illustrates how a user is able to view a weld puddle in virtual reality space and modify his 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 most welding operations are actually performed in the real world. The double displacement layer modeling of the welding physics functionality  1211  run 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 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 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 welding coupon material in accordance with certain embodiments of the present invention. Such subsequent passes may be needed to make a large fillet or groove weld, performed to repair a weld bead formed by a previous pass, for example, or may include a hot pass and one or more fill and cap passes after a root pass as is done in pipe welding. In accordance with various embodiments of the present invention, weld bead and base material may include mild steel, stainless steel, aluminum, nickel based alloys, or other materials. 
       FIGS. 20A-20B  illustrate the concept of a welding element (wexel) displacement map  1420 , in accordance with an embodiment of the present invention.  FIG. 20A  shows a side view of a flat welding coupon (WC)  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. 20B  shows a representation of the top surface  1410  of the simulated WC  1400  broken up into a grid or array of welding elements (i.e., 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. 21  illustrates an example embodiment of a welding coupon space and a weld space of the flat welding coupon (WC)  1400  of  FIG. 20  simulated in the virtual welding system  100  of  FIG. 1 . Points O, X, Y, and Z define the local 3D welding coupon space. In general, each welding coupon type defines the mapping from 3D welding coupon space to 2D virtual reality weld space. The wexel map  1420  of  FIG. 20  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. 21 . A trajectory line from point B to point E is shown in both 3D welding coupon space and 2D weld space in  FIG. 21 . 
     Each type of welding coupon defines the direction of displacement for each location in the wexel map. For the flat welding coupon of  FIG. 21 , 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 welding 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. 22  illustrates an example embodiment of a welding coupon space and a weld space of a corner (tee joint) welding coupon (WC)  1600  simulated in the virtual welding system  100  of  FIG. 1 . The corner WC  1600  has two surfaces  1610  and  1620  in 3D welding coupon space that are mapped to 2D weld space as shown in  FIG. 22 . Again, points O, X, Y, and Z define the local 3D welding coupon space. The texture coordinates of the wexel map are shown as S, T in both 3D welding 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. 22 . A trajectory line from point B to point E is shown in both 3D welding coupon space and 2D weld space in  FIG. 22 . However, the direction of displacement is towards the line X′-O′ as shown in the 3D welding coupon space, towards the opposite corner as shown in  FIG. 22 . 
       FIG. 23  illustrates an example embodiment of a welding coupon space and a weld space of a pipe welding coupon (WC)  1700  simulated in the virtual welding system  100  of  FIG. 1 . The pipe WC  1700  has a curved surface  1710  in 3D welding coupon space that is mapped to 2D weld space as shown in  FIG. 23 . Again, points O, X, Y, and Z define the local 3D welding coupon space. The texture coordinates of the wexel map are shown as S, T in both 3D welding coupon space and 2D weld space, in order to clarify the mapping. A user is to weld from point B to point E along a curved trajectory as shown in  FIG. 23 . A trajectory curve and line from point B to point E is shown in 3D welding coupon space and 2D weld space, respectively, in  FIG. 23 . The direction of displacement is away from the line Y-O (i.e., away from the center of the pipe). 
     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, etc.). 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 embodiment of the present 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 welding 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 embodiment of the present 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 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 embodiment of the present invention, the simulated welding process in virtual reality space works as follows: Particles stream from the emitter (emitter of the simulated MWT  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, etc.) 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 virtual welding system  100  include attraction/repulsion, velocity (related to heat), dampening (related to heat dissipation), direction (related to gravity). 
       FIGS. 24A-24C  illustrate an example embodiment of the concept of a dual-displacement (displacement and particles) puddle model of the virtual welding system  100  of  FIG. 1 . 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. 24A-24C . 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. 24A , the particles  1920  are shown as round un-shaded dots colliding with the current Displacement levels and are piled up. In  FIG. 24B , the “highest” particle heights  1930  are sampled at each wexel location. In  FIG. 24C , 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. 24A-24C , it is possible to visualize the solidification process as the Puddle (shaded rectangles) gradually shrink and the Displacement (un-shaded rectangles) gradually grow 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 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 virtual welding system  100 , 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 PPS  110  remains relatively constant during a simulated welding session. 
     In accordance with an alternate embodiment of the present 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) welding 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 alternate embodiments of the present 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. As used herein, a voxel (e.g., volumetric pixel) is a volume element, representing a value on a regular grid in three dimensional space. 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 embodiment of the present 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 virtual welding system  100  by wexel decimation techniques. If the amount of heat absorbed by a wexel is determined to be too high by the virtual welding system  100 , 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 virtual welding system  100  simulates wexel decimation (taking material away) and wexel reconstitution (i.e., adding material back). Furthermore, removing material in root-pass welding is properly simulated in the virtual welding system  100 . 
     Furthermore, removing material in root-pass welding is properly simulated in the virtual welding system  100 . For example, in the real world, grinding of the root pass may be performed prior to subsequent welding passes. Similarly, virtual welding system  100  may simulate a grinding pass that removes material from the virtual weld joint. It will be appreciated that the material removed may be modeled as a negative displacement on the wexel map. That is to say that the grinding pass removes material that is modeled by the virtual welding system  100  resulting in an altered bead contour. Simulation of the grinding pass may be automatic, which is to say that the virtual welding system  100  removes a predetermined thickness of material, which may be respective to the surface of the root pass weld bead. 
     In an alternative 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 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 virtual welding system  100  also uses three other types of visible particles to represent Arc, Flame, and Spark effects, in accordance with an embodiment of the present 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 welding 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 virtual welding system  100 , in accordance with other embodiments of the present 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 welding 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 virtual welding system  100  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 an alternative embodiment of the present invention, the virtual welding system  100  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 he sets up the system correctly (e.g., correct gas flow rate, correct power cord connected, etc.) In accordance with another alternate embodiment of the present invention, the virtual welding system  100  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 an embodiment of the present invention, a split-screen playback may be provided, allowing two welding sessions to be viewed side-by-side, for example, on the ODD  150 . For example, a “good” welding session may be viewed next to a “poor” welding session for comparison purposes. 
     In summary, disclosed is a real-time virtual reality welding system 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 virtual reality welding system is designed to accommodate portable use, wherein a compactable stand is employed to hold a welding coupon in space for use with the mock welding tool. The mock welding tool includes a common base that can couple to a plurality of adapters, wherein each adapter simulates a particular welding type. In this manner, the system is capable of simulating, in virtual reality space, a weld puddle having real-time molten metal fluidity and heat dissipation characteristics. The system is further capable of displaying the simulated weld puddle on the display device in real-time. 
     The above examples are merely illustrative of several possible embodiments of various aspects of the present invention, wherein equivalent alterations and/or modifications will occur to others skilled in the art upon reading and understanding this specification and the annexed drawings. In particular regard to the various functions performed by the above described components (assemblies, devices, systems, circuits, and the like), the terms (including a reference to a “means”) used to describe such components are intended to correspond, unless otherwise indicated, to any component, such as hardware, software, or combinations thereof, which performs the specified function of the described component (e.g., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the illustrated implementations of the invention. In addition although a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. Also, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in the detailed description and/or in the claims, such terms are intended to be inclusive in a manner similar to the term “comprising”. As utilized herein, the terms “datum” and “datum point” refer to a reference from which measurements are made. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable one of ordinary skill in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that are not different from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.