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Uses 7 iterations of simplex noise to define a 3D density function for the cloud. Each pixel casts a ray that samples the cloud's density at 256 points, and at each of these points a ray is cast to the light source, sampling 256 points along the way to determine how how much the light is blocked. All together, the noise function is sampled 458,752 times per pixel, and this 512*512 image took hours to render.

Raytraced Scene