These changes to how PBR lighting works have been tested by multiple people and determined to be very close to the expected look, better than alternatives tests.
Changes vs dev, are that all PBR lighting is done in linear. And we assume that the vanilla diffuse texture has been premultiplied by the lambert diffuse function, which is (1.0 / PI). This explains why the lambert function is never applied in vanilla / why specular lighting is not multiplied by PI.
Therefore we remove a lot of multiplications by PI and divide the albedo by PI to match the vanilla diffuse brightness.
These changes to how PBR lighting works have been tested by multiple people and determined to be very close to the expected look, better than alternatives tests.
Changes vs dev, are that all PBR lighting is done in linear. And we assume that the vanilla diffuse texture has been premultiplied by the lambert diffuse function, which is (1.0 / PI). This explains why the lambert function is never applied in vanilla / why specular lighting is not multiplied by PI.
Therefore we remove a lot of multiplications by PI and divide the albedo by PI to match the vanilla diffuse brightness.