Direct display of CSG expression by use of depth buffers

Details Direct display of CSG expression by use of depth buffers Direct display of CSG expression by use of depth buffers

1994-09-30

1995-03-28

Zimmerman, Mark K.

395120, 395126, G06T 1710

Patent

active

054025320

ABSTRACT:
Apparatus and method for generating displayable information expressive of a three dimensional solid object. The apparatus includes a processor (12,16) for expressing the object in a Constructive Solid Geometry representation thereof so as to be comprised of one or more primitive objects. The apparatus further includes a processor (18, 20) for repetitively evaluating the one or more primitive objects to determine displayable faces thereof. A depth interval buffer (20) is responsive to the operation of a scan conversion processor (18) for detecting when a predetermined number of repetitive evaluations occur without causing a change in the determination of a displayable face and for causing the operation of the evaluation processor to terminate. Toleranced depth tests are used to remove dangling faces or edges and to properly handle coincident faces. Pixel-centering is employed to improve the accuracy of depth tests and to identify pixels upon which a product projects. Shadowing is accomplished using a two-pass scan-conversion technique with an auxiliary shadow-buffer (ZS).

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Methods for Computer Aided Design of Free-Form Objects, Mathematics and Computer Science Series, No. 56, Helsinki University of Technology, Finland 1990, pp. 3-60.

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