[Feature] Realistic PBR renderer

[brenocq]

Feature description
Atta currently includes basic implementations of various renderers using the Atta Shading Language (ASL). However, the Physically Based Rendering (PBR) renderer needs to be improved. The following images display the current renderer outputs, as seen in the material-resources tutorial for Atta version v0.3.7.

Renderer	Screenshot
Fast Renderer
Phong Renderer
PBR Renderer

If we follow the PBR shader implementation for the LearnOpenGL tutorial, we should achieve something like below

It would be beneficial to improve the PBR renderer to enhance Atta's capabilities for creating more realistic simulations. This includes enabling more accurate depictions of materials, lighting, and camera effects, significantly elevating the visual fidelity and believability of simulations produced with Atta.

Tasks

• Track .asl files with git
• Fix specular reflection
• Environment light
  • Load HDR image
  • Generate Cubemap image from Equirectangular map
  • Skybox pipeline to render environment image in the background
  • Precompute diffuse irradiance cubemap
  • Precompute specular irradiance based on roughness
  • Precompute Fresnel lookup texture
• Directional light shadows
• Point light shadow
• Update material resources tutorial zip

Resources

• LearnOpenGL PBR
• LearnOpenGL Shadow Mapping
• LearnOpenGL Point Shadows

[brenocq]

It's been a long time I don't work in Atta, will try to continue with this task now :)

[brenocq]

Specular reflections are looking nice, but needs some more work on the environment light.

[brenocq]

Skybox rendering

[brenocq]

Irradiance map created correctly! But brdfLUT is wrong (currently it's all black)

[brenocq]

Beautiful BRDF LUT generated by the shader written in ASL (atta shading language)

[brenocq]

Full IBL pipeline implemented

[brenocq]

Directional light shadows