GPU Pro 6

5. Sparse Procedural Volume Rendering 177

Figure 5.9. Propagating light through a metavoxel’s voxels.

Figure 5.10. Procedural colors.

5.5.3 Light Propagation

We propagate light through the metavoxel with a simple loop. We use the ras-

terizer and pixel shader to perform the work. We draw one pixel for each of the

metavoxel’s voxel columns—i.e., a two-triangle quad covering one pixel for each

of our voxel columns (e.g., for a 32 × 32 × 32 metavoxel, we draw a 32 × 32 pixel

square). Our pixel/fragment shader loops over each voxel in the corresponding

voxel column.

178 II Rendering

// 100% l i g h t pr o p agates to start

propagatedLight =1

// Loop over a