Rendering Trees from Precomputed Z-Buffer Views

Parallel projection z-buffer images are precomputed for a number of preset viewing directions on the unit sphere. Using the depth information, we can reconstruct a 3-D point from each image pixel. Then parallel or perspective views can be found from any other viewpoint by rotating the 3-D points from the nearest three or four precomputed views into the proper position and projecting them onto an output z-buffer. A temporary z-buffer image, constructed in the same way for a viewpoint at the light source, is used for a z-buffer shadow algorithm. The rendering algorithm is applied to broad leaf and needle leaf trees, and tested in animation. Our rendering algorithm is similar to that in Chen and Williams [1], with differences listed below.