Shadow Algorithms Data Miner

2.5. Ray Tracing 65

voxels are necessary. When the closest intersected surface is found, the shadow

count is checked. If the count is 0, then the surface is not in shadow; otherwise

the surface is in shadow. However, since it might need to deal with a large num-

ber of shadow polygons, the implementation resorts to the traditional shadow ray

approach under such circumstances.

Vox el Occlusion Testing

For voxel occlusion testing [638], each voxel uses up an extra 2 bits per light

source. Its value indicates the level of opaque occlusion of the voxel with respect

to each light source: full occlusion, null occlusion, and unknown occlusion (see

Figure 2.30). ...