| 摘要 |
PURPOSE:To shorten the processing time required for shading display of a three-dimensional object by reducing the number of times of beam setting for beam tracking and luminance calculation processing. CONSTITUTION:After intersections between a tracking beam and object data are obtained by an intersection calculating means 4, a luminance calculation point where a luminance value is actually calculated is selected from intersections by a luminance calculation point selecting means 5. The distance to the luminance calculation point from the start point of the beam is obtained and is accumulated in a tracking distance storage means 7. Thus, the distance along the beam from the start point to the luminance calculation point is stored in the storage means 7. If this distance is longer than a certain value, the luminance calculation point is very small when viewed from the visual point, namely, on a screen or is smaller than the resolution on the screen and luminance calculation is unnecessary.
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