Fix: EEVEE: runtime-generated BSDF LUT does not match the precomputed LUT #111632

Weizhen Huang · 2023-08-28T20:32:02+02:00

Weizhen Huang commented

2023-08-28 20:32:02 +02:00

RUNTIME_LUT_CREATION is disabled by default, but if set to true,
the new bxdf_lut_frag.glsl should generate the LUT that is submitted
in this commit. This new LUT is very close to the previously stored one.
Generate the LUT by Monte-Carlo sampling with I = 1/N\sum\frac{f}{p},
except that the samples are not random, but mapped from a regular grid,
following previous approach to avoid interpolation artefacts caused by
noise.
Added comments to make the computed quantities and the LUT usage more
clear.
Glass with IOR < 1 is now slightly darker due to single-scattering.
The lost energy will be recovered in a future commit.
The special cases of IOR == 0, roughness == 0 and roughness == 1
are handled well during microfacet sampling and evaluation, no need to
clamp.
When IOR == 1, in theory BRDF is zero and BTDF is one, but we do not
make it a special case to allow smooth transition.

* `RUNTIME_LUT_CREATION` is disabled by default, but if set to `true`, the new `bxdf_lut_frag.glsl` should generate the LUT that is submitted in this commit. This new LUT is very close to the previously stored one. * Generate the LUT by Monte-Carlo sampling with \(I = 1/N\sum\frac{f}{p}\), except that the samples are not random, but mapped from a regular grid, following previous approach to avoid interpolation artefacts caused by noise. * Added comments to make the computed quantities and the LUT usage more clear. * Glass with `IOR < 1` is now slightly darker due to single-scattering. The lost energy will be recovered in a future commit. * The special cases of `IOR == 0`, `roughness == 0` and `roughness == 1` are handled well during microfacet sampling and evaluation, no need to clamp. * When `IOR == 1`, in theory BRDF is zero and BTDF is one, but we do not make it a special case to allow smooth transition.

Weizhen Huang added 1 commit 2023-08-28 20:32:12 +02:00

eb268dcaee Fix: EEVEE: runtime-generated BSDF LUT does not match the precomputed LUT

* `RUNTIME_LUT_CREATION` is disabled by default, but if set to `true`,
the new `bxdf_lut_frag.glsl` should generate the LUT that is submitted
in this commit. This new LUT is very close to the previously stored one.
* Generate the LUT by Monte-Carlo sampling with I = 1/N \sum f/pdf,
except that the samples are not random, but mapped from a regular grid,
following previous approach to avoid interpolation artefacts caused by
noise.
* Added comments to make the computed quantities and the LUT usage more
clear.
* Glass with `IOR < 1` is now slightly darker due to single-scattering.
The lost energy will be recovered in a future commit.

Weizhen Huang added the

Module

EEVEE & Viewport

label 2023-08-28 20:35:32 +02:00

Weizhen Huang requested review from Clément Foucault 2023-08-28 20:35:44 +02:00

Clément Foucault reviewed 2023-08-28 20:46:45 +02:00

Clément Foucault left a comment

Code looks good. Maybe you could use square in many places in these files. I still have to test the changes.

Code looks good. Maybe you could use `square` in many places in these files. I still have to test the changes.

Clément Foucault approved these changes 2023-08-29 13:44:53 +02:00

Weizhen Huang added 2 commits 2023-08-29 14:48:01 +02:00

84795f8aee Merge remote-tracking branch 'origin' into recompute-eevee-bsdf-lut