Blender Git Commits

Fix T85633: Misspelling of "neighborhood" in description

Merge branch 'blender-v2.92-release'

Fix T85488: Display units inset operator

The inset operator would display the inset thickness and depth as
Blender units during transform. This meant that when the scene units
were set to something different than meters, the display value would
give different results than entering the same number using the value
input. (Similar to D10325)

The fix makes sure that the numbers are always displayed in the correct
scene units.

Reviewed By: campbellbarton

Maniphest Tasks: T85488

Differential Revision: https://developer.blender.org/D10366

Cycles: Implement Dwivedi guiding for path-traced subsurface scattering

Cycles has supported path-traced subsurface scattering for a while, but while it's
more accurate than other approaches, the increase in noise makes it an expensive option.

To improve this, this patch implements Dwivedi guiding, a technique that is based on
zero-variance random walk theory from particle physics and helps to produce shorter
random walks with more consistent throughput.

The idea behind this is that in non-white materials, each scattering event inside the
medium reduces the path throughput. Therefore, the darker the material is, the lower the
contribution of paths that travel far from the origin is.
In order to reduce variance, Dwivedi guiding uses modified direction and distance sampling
functions that favor paths which go back towards the medium interface.
By carefully selecting these sampling distributions, variance can be greatly reduced, and
as a neat side effect shorter paths are produced, which speeds up the process.

One limitation of just blindly applying this is that the guiding is derived from the
assumption of a medium that covers an infinite half-space. Therefore, at corners or thin
geometry where this does not hold, the algorithm might lead to fireflies.
To avoid this, the implementation here uses MIS to combine the classic and guided sampling.
Since each of those works on one of the three color channels, the final estimator combines
six sampling techniques. This results in some unintuitive math, but I tried to structure
it in a way that makes some sense.

Another improvement is that in areas where the other side of the mesh is close (e.g. ears),
the algorithm has a chance to switch to guiding towards the other side. This chance is based
on how deep the random walk is inside the object, and once again MIS is applied to the
decision, giving a total of nine techniques.

Combining all this, the noise of path-traced subsurface scattering is reduced significantly.
In my testing with the Rain character model and a simple lighting setup, the path-traced
SSS is now actually less noisy than the Christensen-Burley approximation at same render time
while of course still being significantly more realistic.

Differential Revision: https://developer.blender.org/D9932

Cleanup: spelling

cmake/deps: Update mesa to 20.3.4

This resolves build error with Py3.9x, use meson build system
since autoconf/automake are no longer supported.

This adds ninja & meson as dependencies for Linux.

Reviewed By: brecht, sybren

Ref D10282

Cleanup: Simplify geometry nodes attribute API usage

Getting an "ouput" attribute is equivalent to creating an attribute and
then getting a write attribute. Replace the latter with the former for
consistency with other code, and to decrease the used surface area
of the attribute API to hopefully facilitate future cleanup.

Cleanup: use doxy sections

Cleanup: use return argument prefix

Cleanup: correct/update comments

Cleanup: unused function

Cleanup: remove commented logic for Alt-Pad0 to use previous camera

While this could be useful, it's been removed since 2.4x, keeping this
here doesn't help add it back since it would need to be re-implemented.

Cleanup: spelling

Cleanup: Source Code Typos

Corrects approximately 36 spelling errors in source variable names.

Differential Revision: https://developer.blender.org/D10347

Reviewed by Hans Goudey

EEVEE: Fix glass with sharp distribution not ignoring roughness

EEVEE: Change cubemap roughness fit

This changes the roughness mapping to better utilize the mip chain resolution.
This improves glossy reflections with small roughness.

Lightcache version bumped because old data does not have the same roughness
mapping and cannot be used.

EEVEE: Update Offline LUT

This follows a change in the LUT generation code.

EEVEE: Update LUT GGX generation shader

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

EEVEE: Fix incorrect fresnel function.

The optimized version was not correct. Also it is not showing any benefit
over the non optimized version.

EEVEE: Refactor closure_lit_lib.glsl

This refactor was needed for some reasons:
- closure_lit_lib.glsl was unreadable and could not be easily extended to use new features.
- It was generating ~5K LOC for any shader. Slowing down compilation.
- Some calculations were incorrect and BSDF/Closure code had lots of workaround/hacks.

What this refactor does:
- Add some macros to define the light object loops / eval.
- Clear separation between each closures which now have separate files. Each closure implements the eval functions.
- Make principled BSDF a bit more correct in some cases (specular coloring, mix between glass and opaque).
- The BSDF term are applied outside of the eval function and on the whole lighting (was separated for lights before).
- Make light iteration last to avoid carrying more data than needed.
- Makes sure that all inputs are within correct ranges before evaluating the closures (use `safe_normalize` on normals).
- Making each BSDF isolated means that we might carry duplicated data (normals for instance) but this should be optimized by compilers.
- Makes Translucent BSDF its own closure type to avoid having to disable raytraced shadows using hacks.
- Separate transmission roughness is now working on Principled BSDF.
- Makes principled shader variations using constants. Removing a lot of duplicated code. This needed `const` keyword detection in `gpu_material_library.c`.
- SSR/SSS masking and data loading is a bit more consistent and defined outside of closure eval. The loading functions will act as accumulator if the lighting is not to be separated.
- SSR pass now do a full deferred lighting evaluation, including lights, in order to avoid interference with the closure eval code. However, it seems that the cost of having a global SSR toggle uniform is making the surface shader more expensive (which is already the case, by the way).
- Principle fully black specular tint now returns black instead of white.
- This fixed some artifact issue on my AMD computer on normal surfaces (which might have been some uninitialized variables).
- This touched the Ambient Occlusion because it needs to be evaluated for each closure. But to avoid the cost of this, we use another approach to just pass the result of the occlusion on interpolated normals and modify it using the bent normal for each Closure. This tends to reduce shadowing. I'm still looking into improving this but this is out of the scope of this patch.
- Performance might be a bit worse with this patch since it is more oriented towards code modularity. But not by a lot.

Render tests needs to be updated after this.

Reviewed By: jbakker
Differential Revision: https://developer.blender.org/D10390

# Conflicts:
# source/blender/draw/engines/eevee/eevee_shaders.c
# source/blender/draw/engines/eevee/shaders/common_utiltex_lib.glsl
# source/blender/draw/intern/shaders/common_math_lib.glsl