| 摘要 |
PROBLEM TO BE SOLVED: To reduce an alias which is generated on the silhouette line of a shadow concerning technique for smoothly drawing the silhouette line of the shadow in drawing the shadow with the use of shadow depth buffers in computer graphics. SOLUTION: When a shadow polygon is drawn in a light source coordinate system in the first pass of a shadow silhouette anti-alias circuit, a pixel is defined as a rectangular grid area in addition to the x, y, z coordinate values of an outline in an outline interpolating circuit, so as to obtain information on the inclination, decimal point part, major/minor axis, right/left line, and start/end point, etc., of the polygonal outline. Edge information and the depth value of the polygon corresponding to the information are stored in a plurality of shadow depth buffers. In a second pass, a polygonal interpolation point to be drawn in a view point coordinate system is converted into the light source coordinate system. Then an area is determined through the use of the silhouette line buffer 22, and a means for determining whether the interpolation point belongs to the outside or inside of the shadow polygon using the shadow depth buffers. Comparison is performed with the depth value of the shadow depth buffer held in the area. The juggy of the silhouette line is reduced by a means which defines the interpolation point as the shadow when existing at a position apart from the light source and as a radiation point when existing at a position close to the light source. COPYRIGHT: (C)2006,JPO&NCIPI |
