Another 3D canvas demo

Adapted from vlad's port of FRequency's 1k demo. I made it a bit lighter and fiddled with the lights and colors.

That demo is pretty funky, my understanding is that it uses the fragment shader to raytrace a sine wave function with two lights. For each pixel, search for the nearest depth where the function is below zero. Then find the tangent of the function at that point and dot it with the light direction to do diffuse shading. Finally add fog color depending on the depth of the point.

Why it uses the tangent instead of the normal is still fuzzy to me.