公开(公告)号：CA2052767A1

公开(公告)日：1992-05-16

申请号：CA2052767

申请日：1991-10-04

Applicant: IBM

Inventor： EINKAUF MARK A ,  ROSSIGNAC JAROSLAW R ,  VANOVER MICHAEL T ,  WU JEFFREY

IPC: G06F3/153 ,  G06T15/30 ,  G06T17/20 ,  G06F15/72

Abstract: AT9-90-053 SYSTEM AND METHOD FOR DISPLAYING TRIMMED SURFACES USING BITPLANE MASKING A system and method is provided for displaying trimmed surfaces on a computer graphics system. The present invention tessellates a three-dimensional surface into triangles and determines whether a trimming curve intersects any triangles. If an intersection occurs, a polygon trimming mask is formed by performing an exclusive OR operation and rendering the polygon into a mask plane. The XOR operation sets the bits in the mask plane corresponding to the trimming mask to logical 1. The rendering hardware then compares the bits in the mask plane with the bits in the frame buffer and draws those pixels which correspond to the bits set to 1 in the mask plane. Since, the trimming mask is a polygon the rendering hardware can perform shading, or lighting calculations using values for points which are contained on the tessellated triangle. In this manner, consistent lighting of a trimmed surface can be achieved. Additionally, the present invention provides for the formation of multiple trimming masks when multiple trimming curves intersect a tessellated triangle. The multiple trimming masks are sequentially XORed into the mask plane and the corresponding pixels are then drawn.

公开(公告)号：CA2007790C

公开(公告)日：1994-03-29

申请号：CA2007790

申请日：1990-01-15

Applicant: IBM

Inventor： ROSSIGNAC JAROSLAW R ,  EPSTEIN DAVID A ,  GHARACHORLOO NADER ,  JANSEN FREDERIK W ,  ZOULAS CHRISTOS S

IPC: G06T15/40 ,  G06F15/66 ,  G06F15/72

Abstract: MULTIPLE DEPTH BUFFERS FOR GRAPHICS AND SOLID MODELLING A CSG solid modelling system 10 has a triple z-buffer architecture. For each pixel stored in a pixel memory 12 there are five storage entries grouped into five buffers including a front z-buffer (F) 16 which is employed to store the depths of a front face for a currently processed z-connected product, a back z-buffer (B) 18 which is employed to store the depths of a back face for the currently processed z connected product and a final z-buffer (Z) 20 which stores the front faces of a displayed solid. Two other buffers are an intensity buffer (T) 22 for storing the intensities associated with the front face of the current z-connected product and a final intensity buffer (I) 24 for storing the intensities of the visible faces of the displayed solid. A bus 26 couples these various buffers together and to a processor 28 which may be a central processing unit or a peripheral processor. The system provides for a solid represented by any CSG tree to be represented as a union of z-connected products and that these z-connected products be expressed as intersections of z-connected sweeps. Furthermore it is shown that expressions of z-connected products in terms of sweeps are extracted directly from a CSG tree. Variations of the display methods may be used to detect interferences and differences between solids defined in CSG.