Implement PBR pipeline

[Adnn]

• [x] Basic BRDF implementation:
  • [x] glTF annex B / glTF viewer
  • [x] derivation from rtr 4th
  • [x] Diffuse
  • [x] Specular

    • Note: the book points at optimization to avoid calculating h and to remove chi.

    • find the page number
    • [x] GGX
      • [x] optimizations p 341-342 (9.45)
    • [x] Blinn-Phong
• [x] Implement several approaches to material blending
  • [x] parameters blending (usual for real-time)
  • [x] result blending (more accurate, but slower)-