Conway's World:
Dynamically update a texture with Conway's game of life. Render the
two spheres to look like a world, where the "inhabitants" are rendered
on the outer sphere and shadows of them are rendered on the inner
sphere.
Technical details: The texture is procedurally generated using Conway's game of life, although any procedural system would work well (particle systems would be specifically well suited for this method). The outer sphere is alpha mapped based on whether the cells are alive or dead, and the inner sphere uses the same texture but treats it as a shadow map. Diffuse lighting is toggleable ("o" key), and different shapes can be rendered by hitting the number keys (0, 1, or 2).