Browse Prior Art Database

Construction Solid Geometry Models Where Primitives Are Known to Be Construction Primitives

IP.com Disclosure Number: IPCOM000035303D
Original Publication Date: 1989-Jul-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Todd, SJ: AUTHOR

Abstract

This disclosure relates to Construction Solid Geometry (CSG) in which knowledge about the model is used to speed up realisation. The technique uses truth tables, rather than trees, for tentative edge classification. These tables can be manipulated by bit-wise operators. A test voxel is considered and the number of non-construction primitives counted. If this is zero, the voxel is either fully inside or fully outside the modelled object. Background on Construction Primitives

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Construction Solid Geometry Models Where Primitives Are Known to Be Construction Primitives

This disclosure relates to Construction Solid Geometry (CSG) in which knowledge about the model is used to speed up realisation. The technique uses truth tables, rather than trees, for tentative edge classification. These tables can be manipulated by bit-wise operators. A test voxel is considered and the number of non-construction primitives counted. If this is zero, the voxel is either fully inside or fully outside the modelled object. Background on Construction Primitives

Many solid models contain primitives that are not redundant but are known not to contribute directly to the surface of the model. We call these construction primitives. An example is given by a cylinder with a matching sphere at one end, illustrated in Fig. 1 in cross section. The plane used to terminate the cylinder is a construction plane. Use of Construction Primitives

Construction primitives may play several roles in CSG modelling. They may first be identified in one of several ways: -The user may assert that a particular primitive is a construction primitive. -The system may be generating a solid model and assert that a particular primitive is a construction primitive. -The system may discover during processing that a particular primitive is a construction primitive.

Once a construction primitive has been identified, it may be used in one of two ways. -To optimise subsequent processing. -As a check that the model is not changed to violate the assertion that the primitive is a construction primitive. Efficie...