National Technical Reports Library

The National Technical Information Service acquires, indexes, abstracts, and archives the largest collection of U.S. government-sponsored technical reports in existence. The NTRL offers online, free and open access to these authenticated government technical reports. Technical reports and documents in its repository may be available online for free either from the issuing federal agency, the U.S. Government Publishing Office’s Federal Digital System website, or through search engines.

Details

Algorithm for Projecting Points onto a Patched CAD Model.

DE200415006268

Publication Date	2001
Personal Author	Henshaw, W. D.
Page Count	16
Abstract	We are interested in building structured overlapping grids for geometries defined by computer-aided-design (CAD) packages. Geometric information defining the boundary surfaces of a computation domain is often provided in the form of a collection of possibly hundreds of trimmed patches. The first step in building an overlapping volume grid on such a geometry is to build overlapping surface grids. A surface grid is typically built using hyperbolic grid generation; starting horn a curve on the surface, a grid is grown by marching over the surface. A given hyperbolic grid will typically cover many of the underlying CAD surface patches. The fundamental operation needed for building surface grids is that of projecting a point in space onto the closest point on the CAD surface. We describe a fast algorithm for performing this projection, it will make use of a fairly coarse global triangulation of the CAD geometry. We describe how to build this global triangulation by first determining the connectivity of the CAD surface patches. This step is necessary since it is often the case that the CAD description will contain no information specifying how a given patch connects to other neighboring patches. Determining the connectivity is difficult since the surface patches may contain mistakes such as gaps or overlaps between neighboring patches.
Keywords	Grid generation (Mathematics) Structured grids (Mathematics) Points (Mathematics) Geometry Computation Triangulation Algorithms Software (Computers) Computer aided design (CAD) Patches (Computer coding) Connectivity
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Lawrence Livermore National Lab., CA.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200414

Algorithm for Projecting Points onto a Patched CAD Model.

Algorithm for Projecting Points onto a Patched CAD Model.
DE200415006268

Publication Date	2001
Personal Author	Henshaw, W. D.
Page Count	16
Abstract	We are interested in building structured overlapping grids for geometries defined by computer-aided-design (CAD) packages. Geometric information defining the boundary surfaces of a computation domain is often provided in the form of a collection of possibly hundreds of trimmed patches. The first step in building an overlapping volume grid on such a geometry is to build overlapping surface grids. A surface grid is typically built using hyperbolic grid generation; starting horn a curve on the surface, a grid is grown by marching over the surface. A given hyperbolic grid will typically cover many of the underlying CAD surface patches. The fundamental operation needed for building surface grids is that of projecting a point in space onto the closest point on the CAD surface. We describe a fast algorithm for performing this projection, it will make use of a fairly coarse global triangulation of the CAD geometry. We describe how to build this global triangulation by first determining the connectivity of the CAD surface patches. This step is necessary since it is often the case that the CAD description will contain no information specifying how a given patch connects to other neighboring patches. Determining the connectivity is difficult since the surface patches may contain mistakes such as gaps or overlaps between neighboring patches.
Keywords	Grid generation (Mathematics) Structured grids (Mathematics) Points (Mathematics) Geometry Computation Triangulation Algorithms Software (Computers) Computer aided design (CAD) Patches (Computer coding) Connectivity
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Lawrence Livermore National Lab., CA.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200414