[TRACKER] New nodes in the works

[paddy-exe]

Issue description

General / Usability

• [ ] Sphere Mask (masks the output of another node in a sphere shape (with smooth falloff))
• [ ] Dither Node (see here)

Sky Shader

• [ ] Mie Scattering (Wikipedia article)
• [ ] Rayleigh Scattering (Wikipedia article)
  • Phase function (Henyey-Greenstein) (Scientific paper)
• [ ] Raymarching function (to give a volumetric effect to clouds) (see here)

Water Shader

• [ ] Beer's Law (Wikipedia article)
• [ ] Phase function (Henyey-Greenstein) (Scientific paper)