This modifies the principled BSDF and the Glass BSDF which now
have better fit to multiscatter GGX.
Code to generate the LUT have been updated and can run at runtime.
The refraction LUT has been changed to have the critical angle always
centered around one pixel so that interpolation can be mitigated.
Offline LUT data will be updated in another commit
This simplify the BTDF retreival removing the manual clean cut at
low roughness. This maximize the precision of the LUT by scalling
the sides by the critical angle.
I also touched the ior > 1.0 approximation to be smoother.
Also incluse some cleanup of bsdf_sampling.glsl
- add the use of DRWShaderLibrary to EEVEE's glsl codebase to reduce code
complexity and duplication.
- split bsdf_common_lib.glsl into multiple sub library which are now shared
with other engines.
- the surface shader code is now more organised and have its own files.
- change default world to use a material nodetree and make lookdev shader
more clear.
Reviewed By: jbakker
Differential Revision: https://developer.blender.org/D8306
This augment the existing irradiance grid with a new visibility precomputation.
We store a small shadowmap for each grid sample so that light does not leak through walls and such.
The visibility parameter are similar to the one used by the Variance Shadow Map for point lights.
Technical details:
We store the visibility in the same texture (array) as the irradiance itself (in order to reduce the number of sampler).
But the irradiance and the visibility are not the same data so we must encode them in order to use the same texture format.
We use RGBA8 normalized texture and encode irradiance as RGBE (shared exponent).
Using RGBE encoding instead of R11_G11_B10 may lead to some lighting changes, but quality seems to be nearly the same in my test cases.
Using full RGBA16/32F maybe a future option but that will require much more memory and reduce the perf significantly.
Visibility moments (VSM) are encoded as 16bits fixed point precision using a special range. This seems to retain enough precision for the needs.
Also interpolation does not seems to be big problem (even though it's incorrect).
Early implementation. Slow and still has quality
3 ways of storing irradiance:
- Spherical Harmonics: Have problem with directionnal lighting.
- HL2 diffuse cube: Very low resolution but smooth transitions.
- Diffuse cube: High storage requirement.
Also include some name change.
For now only compute GGX convolution. The GGX LUT used for the split sum approximation (UE4) is merged with the LTX mag LUT that uses the same parameters (theta and roughness)
