C function for shaded rendering
Use shaded rendering in RenderImage
Get shape as object, not pointer

(working on tracking down leaks)
Add yaw and pitch properties for animation
Use free_tree as deleter for tree pointer
First pass at depth-blending images (in software)
Log draw time
Use -O3 in release
QImage-based compositing.

Still too slow -- will switch to height-maps until OpenGL comes along.