[PBR-Sky] Rendering atmospheric light scattering

[T-rvw]

Light scattering is the basic thing to describe the color of the sky.

• Light scattering
  • elastic type - No energy lose. This is the type what we focus on.
  • Rayleigh scattering
  • particles diameter smaller than a value to simulate O2, NO2, CO2
  • affected by the light wavelength
  • blue skylight
  • MIE scattering
  • fog, halos around the sun, gray tones around the cloud
• Combine Rayleigh and MIE
  • Single Scattering
  • Multiple Scattering
• Precomputed atmospheric scattering
  • LUT generate tool
  • https://ebruneton.github.io/precomputed_atmospheric_scattering/demo.html
  • https://github.com/ebruneton/precomputed_atmospheric_scattering
• God Rays
  • halos from the sky to camera. Seems that only a simple post effect.
  • https://www.shadertoy.com/view/4dyXWy
• Reference
  • https://media.contentapi.ea.com/content/dam/eacom/frostbite/files/s2016-pbs-frostbite-sky-clouds-new.pdf
  • https://github.com/sebh/UnrealEngineSkyAtmosphere

[T-rvw]

@Hinageshi01 You can add more details to every feature. Or edit the issue if there is something wrong.

[roeas]

• A Scalable and Production Ready Sky and Atmosphere Rendering Technique
  • https://diglib.eg.org/bitstream/handle/10.1111/cgf14050/v39i4pp013-022.pdf
• GPU Gems 2 Chapter 16. Accurate Atmospheric Scattering
  • https://developer.nvidia.com/gpugems/gpugems2/part-ii-shading-lighting-and-shadows/chapter-16-accurate-atmospheric-scattering
• Fog
  • When we look at an object on the earth surface, we will see the light reflected by the object itself and will also see the light scattered by the atmosphere in the light path
  • https://iquilezles.org/articles/fog/
• God Rays(GPU Gems 3 Chapter 13. Volumetric Light Scattering as a Post-Process)
  • https://developer.nvidia.com/gpugems/gpugems3/part-ii-light-and-shadows/chapter-13-volumetric-light-scattering-post-process
• Sun
  • It Seams that Mie Scattering is enough to express the sun.
• Cloud
  • Clouds should have GodRay with the sun and cast shadows on the ground

[T-rvw]

GPU Pro 7 has a awesome chapter about cloud rendering implementation. Real-Time Volumetric Cloudscapes - Andrew Schneider

Game Engine Gems 3 has a chapter about environment lights from sky to terrain: Realistic Blending of Skies, Water, and Terrain - Frank Kane (Sundog Software, LLC)