This artifact was already present in previous version but was hidden
by the faulty SSS scale.
The issue comes from the translucence using the geometric normal
(computed using fragment shader derivative) leading to poor precision at
depth discontinuity.
Replacing using the same geometric normal reconstruction as the ambient
occlusion pass removes most of the issue.
- 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 was caused by 2 things: Shadow map bias and aliasing.
It made the expected depth of the shadowmap further than the surface
itself in some cases. In normal time this leads to light leaking on normal
shadow mapping but here we need to always have the shadowmap depth above
the shading point.
To fix this, we use a 5 tap inflate filter using the minimum depth of all
5 samples. Using these 5 taps, we can deduce entrance surface derivatives
and there orientation towards the light ray. We use these derivatives to
bias the depth to avoid wrong depth at depth discontinuity in the shadowmap.
This bias can lead to some shadowleaks that are less distracting than the
lightleaks it fixes.
We also add a small bias to counteract the shadowmap depth precision.
