This changes the sampling routine to use the method described in
"A Simpler and Exact Sampling Routine for the GGXDistribution of Visible Normals"
by Eric Heitz.
http://jcgt.org/published/0007/04/01/slides.pdf
This avoids generating bad rays and thus improve noise level in screen-
space reflections / refraction.
This changes the hitBuffer to store `ReflectionDir * HitTime, invPdf`
just as the reference presentation.
This avoids issues when the hit refinement produce a coordinate that
does not land on the correct surface.
We now store the pdf in the same texture and store it inversed so we can
remove some ALU from the resolve shader.
This also rewrite the resolve shader to not be vectorized to improve
readability and scalability.
This is a major rewrite that improves the screen space raytracing
a little bit.
This also decouple ray preparation from raytracing to be reuse in other
part of the code.
This changes a few things:
- Reflections have lower grazing angle failure
- Reflections have less self intersection issues
- Contact shadows are now fully opaque (faster)
Unrelated but some self intersection / incorrect bad rays are caused by
the ray reconstruction technique used by the SSR. This is not fixed by
this commit but I added a TODO.
This removes the need for per mipmap scalling factor and trilinear interpolation
issues. We pad the texture so that all mipmaps have pixels in the next mip.
This simplifies the downsampling shader too.
This also change the SSR radiance buffer as well in the same fashion.
- 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
Using GL_RG16I texture for the hit coordinates increase tremendously the precision of the hit.
The sign of the integer is used to 2 flags (has_hit and is_planar).
We do not store the depth and retrieve it from the depth buffer (increasing bandwith by +8bit/px).
The PDF is stored into another GL_R16F texture.
We remove the raycount for simplicity and to reduce compilation time (less branching in refraction shader).
There was noise correlation between the rotation random number and the radius random number used in the contact shadow algo.
Hacking a new distribution from the old distribution (may not be ideal because it's discrepency may be high)
Also distribute samples evenly on the shadow disc. (add sqrt)
Fix the "bias floating shadows", was cause by the discarding of backfacing geom which makes no sense in this case.
The problem was that orthographic views can have hit position that are negative. Thus we cannot encode the hit in the sign of the Z component.
The workaround is to store the hit position in screenspace. But since we are using floating point render target, we are loosing quite a bit of precision.
TODO: use RGBA16 instead of RGBA16F. But that means encoding the pdf value somehow.
This fix a bug when occluder are on the edge of the screen and occludes more than they should.
Grouped the texture fetches together and clamp the ray at the border of the screen.
Also add a few util functions.
For the moment the only way to enable this is to:
- enable Screen Space REFLECTIONS.
- enable Screen Space Refraction in the SSR parameters.
- enable Screen Space Refraction in the material tab.
