Inside Mengers Pyramid (Shader)

I have procedural generate these by using Shadertoy.

Techinques used:
* Procedural generated in runtime (no models involved)
* Ray Marching
* SDF (signed distance field)
* Menger Sponge fractal algorithm
* Soft Shadow
* 3D texture mapping by code
* AO by using the result of the ray marching process.

Shadertoy: https://www.shadertoy.com/view/3t2SWc