Computer graphics processing and selective visual display system – Computer graphics processing – Three-dimension
Reexamination Certificate
1999-05-24
2003-06-17
Padmanabhan, Mano (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics processing
Three-dimension
C345S420000
Reexamination Certificate
active
06580428
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to providing a computer implemented method for identifying peripheral elements of a geometrical representation of an object. More particularly, the present invention provides a heuristic method for identifying externally visible elements of a geometrical representation of an object.
BACKGROUND
A computer aided design (CAD)/computer aided manufacturing (CAM) system provides a model of a three dimensional object that includes a geometrical representation of the object. CAD/CAM systems also have the ability to rotate these geometrical representations for viewing from different angles.
A designer employing a CAD/CAM system may want to have access to data representing only the outer surfaces of a geometrical representation of an object without having to access data representative of the entire object. In particular, in many design applications, a designer needs to access a geometrical representation of only the outer surfaces of the object to be able to incorporate that object into a structure to be designed. For example, a designer of a motorcycle gas tank may need data corresponding to the surface geometry of the engine, to be able to shape the tank to avoid the engine. Such a designer does not need to know about the interior components of the engine or the detailed structure of the cooling lines to accomplish her task. In an alternative example, a manufacturer intent on protecting proprietary information may want to provide a designer with data corresponding to the outer surfaces of an object without disclosing to the designer the proprietary components and/or structures contained within the object.
A conventional CAD/CAM system, however, does not provide a capability for identifying and extracting peripheral surfaces of a geometrical representation of an object. Thus, a designer employing such a system has to manipulate data corresponding to the entire object, even when she needs only data corresponding to the outer surfaces. The resulting increase in the computational time causes a loss of productivity. In addition, such a conventional system does not allow a user to provide data corresponding to the outer morphology of an object to another party while simultaneously protecting proprietary information regarding components and/or structures within the object.
Thus, it is an object of the present invention to provide a computer implemented method for identifying peripheral elements of a geometrical representation of an object.
It is another object of the present invention to extract peripheral elements of a geometrical representation of an object.
It is yet another object of the present invention to identify peripheral parts and/or sub-assemblies of a complex object formed of a plurality of parts and/or sub-assemblies.
SUMMARY OF THE INVENTION
The present invention solves the above-described limitations of conventional CAD/CAM systems by providing a computer implemented method for identifying peripheral elements of a geometrical representation of an object. The term “peripheral elements”, as used herein, refers to outer surfaces of an object and/or outer sub-assemblies of a complex assembly formed from a plurality of sub-assemblies, and/or outer parts of an object having a plurality of parts. The method of the invention typically receives a geometrical representation that is enclosed in a bounding structure. Alternatively, the method of the invention can receive a geometrical representation that is not enclosed within a bounding structure. In such a case, the method of the invention initially encloses the geometrical representation within a bounding structure, which can have a variety of different shapes. The bounding structure is preferably selected to be a rectangular parallelepiped. It should, however, be understood that the method of the invention is not limited to a particular shape of the bounding structure.
The computer-implemented method of the invention includes a step of sub-dividing the bounding structure into a number of cells. A preferred embodiment of the invention selects the cells to be rectangular parallelepipeds. In a next step, the method of the invention identifies a first subset of the cells, wherein each cell in the first subset contains at least a portion of a surface of the geometrical representation of the object. In a subsequent step, the method identifies a second subset of the cells by iteratively removing from consideration peripheral cells of the bounding structure that are not contained within the first subset. The term peripheral cell, as used herein, refers to a cell that either originally includes an exposed face, i.e., a face not shared with a neighboring cell, or attains an exposed face upon removal of a neighboring cell. Finally, the method identifies the outermost cells of the second subset, thereby identifying the outer elements of the geometrical representation. If an outermost cell contains portions of a plurality of different surfaces of the geometrical representation, the method of the invention can optionally employ a ray tracing procedure to determine which among those surfaces are outermost.
One aspect of the method of the present invention relates to an approximate identification and extraction of those surfaces of a computer generated representation of an object that correspond to externally visible surfaces of the object. In particular, the method of the invention can provide a computer generated display of such surfaces without displaying components and/or structures contained within an envelope of the object formed by such external surfaces.
According to yet another aspect of the invention, a computer-readable medium is provided that holds computer-executable instructions for identifying peripheral elements of a geometrical representation through the method of the present invention.
Another aspect of the present invention relates to providing in a computer platform having a facility for generating a geometrical representation of an object, a transmission medium for transmitting computer-executable instructions for performing the method of the invention for identifying the peripheral elements of the geometrical representation.
The method of the present invention can be practiced in any computer platform having a facility for generating a visual graphical representation of an object. Such a facility may include, but is not limited to, a CAD/CAM system. A CAD/CAM system is particularly suited for implementation of the method of the invention. In particular, the method of the present invention can be incorporated into a CAD/CAM system as one of the utilities provided by such a system. One advantage of implementing the method of the invention in a CAD/CAM system is that many designers are familiar with such systems. Further, such systems provide capabilities for various manipulations of a geometrical representation of an object, typically referred to in a CAD/CAM system as a model, such as rotation of the model so that it can be viewed from various angles.
Illustrative embodiments of the present invention will be described below relative to the following drawings.
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Elnitsky Serge
Ryan Kevin M.
Lahive & Cockfield
Padmanabhan Mano
Parametric Technology Corporation
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