That was only needed in the beginning, when we did not had support for tangents. It's time to clean some of the defines up, it's getting a bit too much.
* __VOLUME__ is basic volume support with Emission and Absorption.
* __VOLUME_SCATTER__ enables volume Scattering support.
* __VOLUME_DECOUPLED__ enables Decoupled Ray Marching.
This problem was introduced in 983cbafd18
Basically the issue is that we were not getting a unique index in the
baking routine for the RNG (random number generator).
Reviewers: sergey
Differential Revision: https://developer.blender.org/D749
* Don't compute expf() for every step, instead sum the intermediate values and calculate it every N (8 for now) steps. This helps a few percent (~5% on a cube with wave texture) in my tests here.
Root of the issue goes back to the on-fly normals commit and the
latest fix for it wasn't actually correct. I've mixed two fixes
in there.
So the idea here goes back to storing negative scaled object flag
and flip runtime-calculated normal if this flag is set, which is
pretty much the same as the original fix for the issue from me.
The issue with motion blur wasn't caused by the rumtime normals
patch and it had issues before, because it already did runtime
normals calculation. Now made it so motion triangles takes the
negative scale flag into account.
This actually makes code more clean imo and avoids rather confusing
flipping code in mesh.cpp.
We can't really make CPU and GPU results look the same in all possible
circumstances, but here we can make them look close enough to each other
by making it so sobol pattern for bounce number is the smae for both
CPU and GPU.
This makes CPU and GPU render results look the same with low number of
samples, high number of samples was never an issue.
Fix T41115: Motion Blur renders Objects Black - But not in Viewport Preview
This actually extends previous fix to normals and makes it all much nicer now.
Worth doing some intense testing, quick one worked just fine but there always
could be some corner cases.
Fix T41079: Solid black render of object with negative scale and smooth shading
In both cases the issue was caused by negative scaled objects with single mesh
users for which scale gets applied when using static BVH.
Since the on-fly normals calculation land normals for such cases weren't flipped
leading them to point to a wrong direction.
Added a special object flag for this, which is a bit of a bummer because now
we've got less bits for real useful things, but this is the only way to get
proper normals without adding more complexity in the on-fly calculations.
* malloc() is used now, which is supported since sm_20: http://docs.nvidia.com/cuda/cuda-c-programming-guide/index.html#dynamic-global-memory-allocation-and-operations The performance of this needs to be tested on various cards still.
* This also works for Heterogeneous Decoupled Ray Marching, but in this case I get sporadic "Illegal Address" errors on my Geforce 540, therefore I did not remove the GPU check in kernel_volume_use_decoupled() yet.
I would appreciate some tests from people who compile themselves, enable Volumetrics in kernel_types.h.
* CUDA can be compiled with Volume support again, change line 78 kernel_types.h for that.
Volumes are still fragile on GPU though, got some Memory/Address CUDA errors in tests.. needs to be investigated more deeply.
Volume scatter might happen before path termination, so
need to check transparent bounces and consider shadow an
opaque when max transparent bounces are reached.
TODO: CPU code seems to have different branching in conditions
which made me thinking it does different things with volume
attenuation, but from the render results it seems the same
exact things are happening there. Worth looking into making
simplifying code a bit here to improve readability.
It turns out that the new Beckmann sampling function doesn't work well with
Quasi Monte Carlo sampling, mainly near normal incidence where it can be worse
than the previous sampler. In the new sampler the random number pattern gets
split in two, warped and overlapped, which hurts the stratification, see the
visualization in the differential revision.
Now we use a precomputed table, which is much better behaved. GGX does not seem
to benefit from using a precomputed table.
Disadvantage is that this table adds 1MB of memory usage and 0.03s startup time
to every render (on my quad core CPU).
Differential Revision: https://developer.blender.org/D614
