Abstract:
The complexity of a CAD model is reduced while its kinematic integrity is maintained by unloading certain data associated with the CAD model from the main memory of a computing device used in the design of the CAD model. The unloaded data includes graphics data and geometry data of those components of the CAD model that the user selects to suppress. The constraint data of the suppressed components are, however, retained in main memory so that the movements of the components of the CAD model can be modeled accurately. By unloading data from the main memory, the overall performance of the computing device is improved and also frees up memory resources for other uses.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/785,544, entitled “Level of Detail, Multi-Sheet and Hidden Line,” filed Mar. 23, 2006, the entire contents of which are incorporated by reference herein. 
     
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention generally relates to computer-aided design and, more particularly, to a method for reducing the complexity of computer-aided design models while maintaining the kinematic relationships of all the components. 
         [0004]    2. Description of the Related Art 
         [0005]    The term computer-aided design (CAD) generally refers to a broad variety of computer-based tools used by architects, engineers, and other construction and design professionals. CAD applications may be used to construct computer models representing virtually any real-world construct. For example, CAD applications are frequently used to create two-dimensional (2D) and three-dimensional (3D) models of mechanical devices. A popular CAD application that is used to construct 3D models of mechanical devices is the Autodesk® Inventor software application program. 
         [0006]    3D models developed for mechanical designs can be extremely large and very complex, consisting of tens of thousands of individual elements, assemblies and constraints. Despite the speed and memory capacity of modern computers, large models can significantly degrade computer performance and response times. Moreover, their sheer complexity makes it difficult to navigate through the model space and to work with elements of interest. 
         [0007]    A variety of techniques exist to reduce complexity and improve performance. The Autodesk® Inventor software application program, for example, allows users to make components invisible, making other parts of the model easier to visualize and navigate. This technique, however, does not improve computer performance and response times very much, because the components that are made invisible are still loaded into memory. Users may, on the other hand, elect to completely skip the loading of a component, but doing this destroys the kinematic integrity of the model. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention provides a method for reducing the complexity of a CAD model while maintaining its kinematic integrity, and a computer readable medium comprising instructions that cause a computing device to perform this method. The reduction in the complexity of the CAD model is achieved by unloading certain data associated with the mechanical design from system memory of a computing device used in the design of the CAD model. The unloaded data includes graphics data and geometry data of those components of the CAD model that the user selects to suppress. By unloading such data from the system memory, the overall performance of the computing device is improved and also frees up memory resources for other uses. 
         [0009]    The constraints data of the suppressed components are, however, retained in system memory so that the movements of the components of the CAD model can be modeled accurately. Other data of the suppressed components that may be retained in memory include mass properties data. 
         [0010]    According to another aspect of the present invention, a usage meter for system memory allocated to a CAD application is provided and updated in real-time so that the user can monitor the system memory usage as he or she is reducing the complexity of the CAD model by suppressing components. In addition to the usage meter for the system memory, the user is also provided with indicators that show how many component occurrences (i.e., the total number of components regardless of whether they are unique or not) are currently in the CAD model and how many unique components are currently loaded into the CAD model. 
         [0011]    In one embodiment, the suppressed components are not displayed in the graphics window. In another embodiment, the suppressed components are displayed in the graphics window as bounding boxes that are highlighted when they are selected. In still another embodiment, the suppressed components are displayed as substitute components which may be illustrated in varying degrees of complexity. 
         [0012]    A CAD model with suppressed components may be saved as a representation object and imported into a larger assembly, and the larger assembly can associatively call upon the representation object of its child assemblies. Child assemblies are also permitted to have sub-assemblies with suppressed components and representation objects defined with respect thereto. Further, any of the representation objects of child assemblies may constitute substitute components. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a conceptual block diagram of a computer system with which embodiments of the present invention can be practiced. 
           [0014]      FIGS. 2A-2B  schematically illustrate the contents of memory units of a computer system that is executing a CAD application in accordance with embodiments of the present invention. 
           [0015]      FIG. 3  illustrates a sample GUI using which suppressed components can be selected and organized. 
           [0016]      FIGS. 4A-4E  illustrate the process of selecting a component to be suppressed and working with an assembly that has a suppressed component. 
           [0017]      FIGS. 5A-5B  respectively illustrate a sample CAD model with no suppressed components and the same CAD model has a suppressed component displayed as a bounding box. 
           [0018]      FIGS. 6A-6B  illustrate a sample browser panel with various “Level of Detail” representation nodes. 
           [0019]      FIGS. 7A-7B  respectively illustrate a sample CAD model with no suppressed components and the same CAD model represented with a substitute component. 
           [0020]      FIG. 8  is a flow diagram that illustrates the steps carried out to manage usage of computer system memory according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]      FIG. 1  is a conceptual block diagram of a computer system  100  with which embodiments of the present invention can be practiced. The components of the computer system  100  illustrated in  FIG. 1  include CAD application  105 , graphical user interface (GUI)  110 , CAD drawing  120 , user input devices  130 , and a display device  115 . CAD application  105  is a software application that is stored in memory and executed by the processor of the computer system  100 . It includes software program routines or instructions that allow a user interacting with GUI  110  to create, view, modify and save CAD drawing or model  120 . In the examples provided herein, the CAD application  105  is the Autodesk® Inventor software application program (Release 11) and associated utilities. Typically, user input devices  130  include a mouse and a keyboard, and display device  115  includes a CRT monitor or LCD display. 
         [0022]    The configuration of the memory units of the computer system  100  is shown in  FIG. 2A . The memory units are interfaced with a processor  210  and include a main memory  220  and a secondary memory  230 . The main memory  220 , also referred to as system memory or computer system memory, is typically configured as random access memory (RAM). The secondary memory  230  has slower access speeds than the main memory  220  and is typically configured as magnetic memory, such as a hard disk. When CAD application  105  is selected to be run on the computer system  100 , a copy of CAD application  105  is retrieved from the secondary memory  230  and stored in the main memory  220 . When a user opens CAD model  120  within CAD application  105 , CAD model  120  is also stored in the main memory  220 . 
         [0023]      FIG. 2B  schematically illustrates the contents of the main memory  220  when CAD model  120  is stored therein. The contents include constraints data for the top-level assembly of CAD model  120 . The constraints data define motion constraint relationships between all of the components in the top-level assembly. The contents also include a dataset for each of the components of the top-level assembly. A component may be a part or a sub-assembly. The dataset for a part includes graphics data, geometry data, and mass properties data. The dataset for a sub-assembly includes constraints data for the sub-assembly and datasets for components that are in the sub-assembly. 
         [0024]    In the example shown in  FIG. 2B , the components of the top-level assembly include Parts A and B and a sub-assembly. The components of the sub-assembly include Parts A and C. Part A under the top-level assembly and Part A under the sub-assembly are different instances of the same component, Part A. 
         [0025]    The present invention provides GUI tools included in CAD application  105  for specifying components of CAD model  120  to be suppressed. A sample GUI according to an embodiment of the present invention is illustrated in  FIG. 3 . The GUI  300  includes a graphics window  310  in which CAD model  120  is displayed, and two GUI control panels comprising a tool panel  320  and a browser panel  330  that lists components of CAD model  120 . 
         [0026]    When CAD model  120  is opened, components of CAD model  120  are loaded into main memory. Some components, like “HANDLE CAP,” are loaded once but may appear more than once in the graphics window  310 . Each such instance of the component is referred to as a component occurrence. The GUI  300  provides an indicator  341  to signify the number of component occurrences existing in main memory, and an indicator  342  to signify the number of components loaded into main memory. The GUI  300  also provides indicator  343 , which is a meter that displays the amount of main memory allocated to CAD application  105  that has been used up by the CAD model  120 . The light region indicates the amount of consumed memory as a percentage of total memory available. 
         [0027]    A component status, “Suppress,” is provided as a way to limit the amount of data loaded for a given component. A component enters this status when a user selects the option “Suppress” on the component&#39;s context menu, which is brought up by a right-click of an input pointing device while the cursor of the input pointing device is positioned over the component.  FIG. 4A  shows the context menu for the component “LEVER ARM: 1 ” and the selection of the option “Suppress” on this context menu. 
         [0028]      FIG. 4B  shows the changes to the graphics window  310 , the browser panel  330  and indicators  341 ,  342 ,  343  when a component is suppressed. First, the display of the lever arm which should appear between end caps  411 ,  412  is suppressed. Second, the component that has been suppressed is shown in the browser panel  330  with a line stricken through it and the text “(Suppressed)” appended to it. Third, indicator  341  is updated to show one less component occurrence, and indicator  342  is updated to show one less loaded component. Fourth, indicator  343  is updated to show an increase in the free memory bar and a decrease in the used memory bar. However, the free memory increase is so slight in this example that the change in indicator  343  is not evident from  FIG. 4A  to  FIG. 4B . 
         [0029]    When a component is suppressed, some of the component&#39;s data are unloaded from main memory. The unloaded data includes graphics data and geometry data. The retained data includes mass properties data and constraints data of the component that define the constraint relationships between the component and the other components in CAD model  120 . The gain in free memory achieved by suppressing a component is the result of unloading that component&#39;s graphics data and geometry data from main memory. 
         [0030]    By retaining the constraints data of the suppressed component, CAD application  105  is able to accurately model the movements of the components relative to all of the other components. The accurate modeling of the movements of the components relative to the other components is reflected in  FIGS. 4B and 4C . In  FIG. 4B , end caps  411 ,  412  are in their initial positions. End caps  411 ,  412  are moved to a new position using an input pointing device (e.g., by clicking on one of end caps  411 ,  412  with the input pointing device and dragging it to a new position) and cause a rotation of pinion shaft  420  and a movement of ram  430  as shown in  FIG. 4C . 
         [0031]      FIG. 4D  shows the context menu for the component “PINION SHAFT: 1 ” and the selection of the option “Suppress” on this context menu so as to cause the suppression of this component.  FIG. 4E  shows the changes to the graphics window  310 , the browser panel  330  and indicators  341 ,  342 ,  343  when the pinion shaft component is suppressed. First, the display of the pinion shaft is suppressed. Second, the pinion shaft component is shown in the browser panel  330  with a line stricken through it and the text “(Suppressed)” appended to it. Third, indicator  341  is updated to show one less component occurrence, and indicator  342  is updated to show one less loaded component. Third, indicator  343  is updated to show an increase in the free memory bar and a decrease in the used memory bar. However, the free memory increase is again so slight in this example that the change in indicator  343  is not evident from  FIG. 4D  to  FIG. 4E . 
         [0032]    As a result of the pinion shaft component being suppressed, some of this component&#39;s data are unloaded from main memory. The unloaded data includes graphics data and geometry data. The retained data includes mass properties data and constraints data of this component that define the constraint relationships between this component and the other components in CAD model  120 . The gain in free memory achieved by suppressing a component is the result of unloading this component&#39;s graphics data and geometry data from main memory.  FIG. 4E  also shows that end caps  411 ,  412  have moved to a new position to cause a movement of ram  430 . The movement of the end caps also causes a rotation of the pinion shaft but this is not visible as the pinion shaft component has been suppressed. 
         [0033]    According to another embodiment of the present invention, a component that is suppressed may be displayed as a bounding box in the graphics window  310  when the component is selected in the browser panel  330 . The bounding box assists the user in understanding where that component is in relation to visible components. The use of the bounding box is illustrated in  FIGS. 5A-5B .  FIG. 5A  represents a CAD model with no components suppressed.  FIG. 5B  represents the same CAD model with a suppressed component. The suppressed component is displayed in  FIG. 5B  as a bounding box  510 . 
         [0034]    The browser panel  330  includes a representation toolset that allows access to a new representation type, Level of Detail (LOD). The LOD representation allows the user to define and save an assembly with suppressed components, so that it can be recalled and reused easily. For example, after having created and saved an LOD representation for an assembly, the user can import that LOD representation into a larger assembly. In an embodiment of the present invention illustrated herein, four default LOD representations can be created with any new assembly. They include:
       Master: All components are loaded.   All Components Suppressed: CAD model assembly is opened with no children components loaded at all.   All Parts Suppressed: All components that are assemblies are loaded, but components that are parts are not loaded, so that the user can get a quick view of the assembly structure from the browser panel.   All Content Center Suppressed: All content library components, e.g., bolts, nuts and washers, are suppressed.       
 
         [0039]      FIG. 6A  is a sample browser panel that includes the four default LOD representations. In  FIG. 6A , however, none of the four default LOD representations has been selected by the user. Instead, a user-defined LOD representation, “Main Body Only,” has been selected by the user. The components that are suppressed are all part of the main body and include: pump_cylinder_housing: 1 , diaphragm_asm: 1 , and hose_connection_asm: 1 . 
         [0040]    When a component is suppressed, and CAD application  105  detects other occurrences of the same component in session which remain fully loaded, a prompt is presented to the user to indicate that memory savings will only be realized if all occurrences of the same component are suppressed. The message may read: “One or more occurrences of the selected component remain unsuppressed. To gain capacity improvements, please suppress all occurrences of this selected component.” 
         [0041]    An assembly can associatively call upon an LOD representation from a child sub-assembly (at any depth). This is illustrated in  FIG. 6B . In  FIG. 6B , there are two nested LOD representations. The top assembly has an LOD representation “No Hydraulics” which is pointing to an LOD representation of the same name from the immediate child sub-assembly, “pump:1.” In turn, the LOD representation in “pump:1” is referencing an LOD representation of the same name in the sub-assembly, “valve_stroke adjust:1.” It is this final LOD representation which governs the suppression status of all children below “valve_stroke_adjust:1.” 
         [0042]    An assembly may be represented as a substitute component. A substitute component is a component which is loaded in the place of the assembly and typically has all of the child components of the assembly suppressed. The substitute component enhances the user&#39;s ability to visualize the interaction of components without paying the performance penalty of loading an editable version into main memory. Substitute components can be user-developed geometry, or automatically created by the computer system, for example, by performing a Boolean operation on all the parametrically developed pieces of the component. 
         [0043]      FIG. 7A  illustrates an assembly with no components suppressed.  FIG. 7B  illustrates a substitute component for the assembly in  FIG. 7A  with all of child components of that assembly suppressed. The substitute component in  FIG. 7B  is represented by a bounding box  710 . In those cases where the user may desire less simplification, the user can unsuppress some of the child components of the assembly. A substitute component is managed through the browser panel  330 , and may be deleted, opened for editing or updating, or copied. 
         [0044]    The substitute component created in the manner described above may be placed into a larger assembly. The substitute status of a component is occurrence based, and thus it is possible to load a substitute component for several occurrences of a given assembly in a larger assembly, but load the master LOD representation in another instance. When this happens, a prompt is presented to the user to indicate that memory savings from the substitute component will only be realized if all occurrences of the same component are substituted. 
         [0045]      FIG. 8  is a flow diagram that illustrates the steps carried out by a computer system that is hosting CAD application  105  to manage the usage of system memory or main memory of the computer system, according to an embodiment of the present invention. In step  810 , an assembly of a CAD model is loaded into system memory. After the assembly is loaded, CAD application  105  monitors inputs made through the browser panel  330  and checks if any of the inputs are for suppressing a component of the assembly (step  812 ). If there is an input for suppressing a component of the assembly, the graphics and geometry data of the selected component are unloaded from system memory (step  814 ). The constraints data and the mass properties data, on the other hand, are not unloaded and retained in the system memory. In step  816 , the memory usage meter and the other indicators for component occurrences and loaded components are updated. The flow then returns to step  812  where CAD application continues to check for inputs for suppressing other components. The assembly with one or more suppressed components can be saved at any time through the browser panel  330 . It can also be copied into a larger assembly as a component or sub-assembly of the larger assembly. 
         [0046]    While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.