Computer graphics processing and selective visual display system – Computer graphics processing – Three-dimension
Reexamination Certificate
1998-12-24
2002-09-03
Zimmerman, Mark (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics processing
Three-dimension
C345S420000, C345S423000
Reexamination Certificate
active
06445390
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to computer technology and, in particular, to computer applications for processing of triangulated surfaces and Cartesian mesh generation.
BACKGROUND OF THE INVENTION
Adaptive Cartesian mesh solutions have been attempted for problems involving complex geometries. Flow solvers and mesh generation schemes for use with arbitrary geometries have been sought. Some approaches have included beginning with a surface triangulation constrained to the intersection curves of particular components. In contrast, a component based approach requires that each element of a geometry be described as a single closed entity. However, using the component based approach adds complexity during grid generation. Since components may overlap, Cartesian cell surface intersections must be characterized and those internal to components must be rejected. Such rejection filtering increases complexity. Assembling surface geometries and creating volume grids on a computer (for example, for computational physics simulations) is accordingly a difficult and time-consuming process. Thus, there is a need to improve accuracy and efficiency of the computerized surface creation, component definition, and volume mesh generation. It is desirable that an automatic method for discretizing the domain around arbitrarily complex geometries be accomplished.
SUMMARY OF THE INVENTION
According to the present invention, computer techniques for processing of triangulated surface geometry and Cartesian mesh generation is made particularly robust and efficient. In particular according to the present invention, complex two and three dimensional computer configurations are produced from combinations of simpler components. Portions of components that lie inside of other components are automatically trimmed away according to the present invention, leaving only the external (exposed) portions of the selected component collection. The intersections between components are accurately expressed in the resultant triangulation.
According to one embodiment of the present invention, geometric degeneracies (tie breaking) are unambiguously resolved. Efficient data structures are selectively stored in computer memory, and specialized techniques, including those from computational geometry and computer graphics, are used to generate a body-intersecting Cartesian volume mesh that discretizes the surrounding flow field.
According to the present invention, the creation of complex surface definitions is simplified. Further according to the present invention, selected complex surface definitions are made accurate and precise to a degree not known in the prior art. Accordingly, accurate computational aerodynamic performance estimation is facilitated. Additionally, Cartesian grid generation is made more effective. More specifically, the computer system according to the present invention forms the Boolean union of multiple-component geometries, and eliminates selected portions of the assembled geometry that are within the assembled geometry and thus hidden from exterior view. According to the present invention, computations of surface-related quantities are computed with increased accuracy, enabling the effective production of data images describing features such as for example, without limitation, the exposed surface area and the internal volume of a selected structure, to produce a structure descriptive information dataset representing processed surface data. The processed surface data is then provided to the volume mesh generator for further computation. A surrounding flowfield for the selected structure is automatically discretized into rectangular hexahedra (cells), with the size of the hexahedra being reduced in areas of large surface curvature or strong flow field gradients. Cells that are split into multiple distinct and unconnected regions by thin pieces of the surface are identified, and the individual regions are marked and saved in the computer memory for use, for example, in flow field simulations. According to the present invention, a Cartesian mesh generation system is provided that is capable of identifying and correcting cells that are split into distinct, unconnected regions. For example and without limitation, the disclosed technology may be employed for applications that include aerodynamic performance estimation and optimization for ground and aerospace vehicles; computer-based geometry modeling (CAD/CAM) systems; rapid prototyping systems (sterolighography); computer-based visualization systems (medical, chemical, and other imaging); computational physics modeling systems (CEM/CFD, etc.); semiconductor device modeling; and internet and data transfer applications (including substantial reductions in the size of VRML and other geometry-related datasets).
REFERENCES:
patent: 5522019 (1996-05-01), Bala et al.
Sugihara “An Intersection Algorithm Based on Delaunay Triangulation”, IEEE, Mar. 1995, pp. 59-67.*
Agrawala et al. “3D Painting on Scanned Surfaces”, ACM Apr. 1995, pp. 145-150.*
Livnat et al. “A Near Optimal Isosurface Extraction algorithm Using the Span Space”, IEEE, 1996, pp. 73-84.*
Aftosmis, M.J., “Emerging CFD Technologies and Aerospace Vehicle Design,” NASA Wkshp .on Surf. Mod., Grid Gen., and Related Issues in CFD, NASA Lewis Rsch Cntr., May 9-11, 1995.
Aftosmis, M.J., Melton, J.E., and Berger, M.J., “Adaptation and Surface Modeling for Cartesian Mesh Methods,” AIAA Paper 95-1725-CP, Jun., 1995.
Aftosmis Michael J.
Berger Marsha J.
Melton John E.
Nguyen Kimbinh T.
Padilla Robert M.
The United States of America as represented by the Adminstrator
Warsh Kenneth L.
Zimmerman Mark
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