FAST SHADOWING ALGORITHM FOR LINEAR LIGHT-SOURCES

This paper presents a fast shadowing algorithm for linear light sources that uses a ray-oriented buffer. Space segmentation by the buffer guarantees that ifa point is included in a subspace, all light rays toward the point are also contained in the subspace. Each cell of the buffer stoves a list of objects that lie within or intersect the subspace allocated to the cell, Therefore, candidate objects, those that may cast shadows onto a point, are determined by referring to the cell where the point is mapped. In addition, whether each candidate object actually casts shadows or not is tested with the bounding-volume of the shadow space to reduce the number of objects subjected to expensive light clipping. The bounding-volumes are also stored in the buffer. For efficiently generating the ray-oriented buffer, we present the cylindrical scan-conversion algorithm. The algorithm preconverts objects' surfaces to trapezia to decrease the Eight clipping cost, then connects the trapezia to the buffer cells. Due to the above improvements, our algorithm achieves over 10 times faster shadow generation compared to the conventional methods. Experimental results confirm that our method can generate realistic images with soft shadows in a few minutes.