Assignment: procedural shading, any kind

My picture: "Planet Dance" or "Fun With Fractal Noise"

Images are linked rather than in-lined due to the large size of some of them. First off, the main submissions:

• Planet Dance (small uncompressed JPEG: 256K, 490x680 pixels)
• Planet Dance (large uncompressed JPEG: 1.88M, 1470x2040 pixels)

All these images were rendered on Evans running Photorealistic Renderman. Most took from 10-30 seconds to render, except for the large final image, which took upwards of ten minutes.

Everything you see is some variation on a fractal noise procedural shader. To create the planets' terrains, a fractal noise displacement shader is aligned exactly with a fractal noise color shader, applied to a sphere. The effect is that color changes precisely with elevation, giving the nice 'snow-capped mountain' effect that is visible on the Earth-like planet. The oceans (when they exist) are simply a second sphere aligned with a particular radius of the terrain sphere. The clouds are a third centered sphere; this one has a fractal noise shader controlling the opacity of the cloud cover. Even the stars are a fractal noise shader: the value of the noise at a given point determines the probability of a star appearing there.

So the three important shaders are: terrain, tercolor, and tcoulds. They are all parameterized sufficiently to allow the variation shown in the different planets of the final picture without recompiling any shaders.

Finally, here's some other example images from various stages of development:

• Early version of terrain shader with ocean.
• Early clouds with some experimental terrain parameters.
• Earth: Final terrain, too many clouds, no terrain coloring yet.
• Earth: Finished version.
• planet Nemesis in development.