Previously, Cycles only supported the Henyey-Greenstein phase function for volume scattering.
While HG is flexible and works for a wide range of effects, sometimes a more physically accurate
phase function may be needed for realism.
Therefore, this adds three new phase functions to the code:
Rayleigh: For particles with a size below the wavelength of light, mostly athmospheric scattering.
Fournier-Forand: For realistic underwater scattering.
Draine: Fairly specific on its own (mostly for interstellar dust), but useful for the next entry.
Mie: Approximates Mie scattering in water droplets using a mix of Draine and HG phase functions.
These phase functions can be combined using Mix nodes as usual.
Co-authored-by: Lukas Stockner <lukas@lukasstockner.de>
Pull Request: https://projects.blender.org/blender/blender/pulls/123532
This enables most of the GPU compiler's optimizations while -ffast-math
isn't set at DPC++ level.
It brings an overall 1% speedup and currently doesn't change the unit
tests pass rate.
This change switches Cycles to an opensource HIP-RT library which
implements hardware ray-tracing. This library is now used on
both Windows and Linux. While there should be no noticeable changes
on Windows, on Linux this adds support for hardware ray-tracing on
AMD GPUs.
The majority of the change is typical platform code to add new
library to the dependency builder, and a change in the way how
ahead-of-time (AoT) kernels are compiled. There are changes in
Cycles itself, but they are rather straightforward: some APIs
changed in the opensource version of the library.
There are a couple of extra files which are needed for this to
work: hiprt02003_6.1_amd.hipfb and oro_compiled_kernels.hipfb.
There are some assumptions in the HIP-RT library about how they
are available. Currently they follow the same rule as AoT
kernels for oneAPI:
- On Windows they are next to blender.exe
- On Linux they are in the lib/ folder
Performance comparison on Ubuntu 22.04.5:
```
GPU: AMD Radeon PRO W7800
Driver: amdgpu-install_6.1.60103-1_all.deb
main hip-rt
attic 0.1414s 0.0932s
barbershop_interior 0.1563s 0.1258s
bistro 0.2134s 0.1597s
bmw27 0.0119s 0.0099s
classroom 0.1006s 0.0803s
fishy_cat 0.0248s 0.0178s
junkshop 0.0916s 0.0713s
koro 0.0589s 0.0720s
monster 0.0435s 0.0385s
pabellon 0.0543s 0.0391s
sponza 0.0223s 0.0180s
spring 0.1026s 1.5145s
victor 0.1901s 0.1239s
wdas_cloud 0.1153s 0.1125s
```
Co-authored-by: Brecht Van Lommel <brecht@blender.org>
Co-authored-by: Ray Molenkamp <github@lazydodo.com>
Co-authored-by: Sergey Sharybin <sergey@blender.org>
Pull Request: https://projects.blender.org/blender/blender/pulls/121050
Temporarily disable point cloud rendering in HIPRT to fix a performance
regression triggered by increased register preasure until
a better solution can be developed.
Pull Request: https://projects.blender.org/blender/blender/pulls/127738
VDB files would fail to render in HIP-RT because NanoVDB wasn't
enabled when compiling HIP-RT kernels, resulting in NanoVDB textures
not being sampled and a blank result being returned instead.
The fix is to enable NanoVDB when compiling HIP-RT kernels.
Ref: #125086
Pull Request: https://projects.blender.org/blender/blender/pulls/127384
The same random number was used for sampling color channel at each step,
which leads to bias. Fixed by rescaling the random number.
Another possibility would be to scramble `rng_offset` and use a new
random number each time, similar as in subsurface scattering, but
rescaling random number should be faster than computing a new one, and
is favorable here since the precision here is not very important
Pull Request: https://projects.blender.org/blender/blender/pulls/127454
The device code was disabled for primitives with deformation blur
and the intersection function always returned false, hence no
rendered primitive.
Other than that, there were a few bugs on both device and host codes
(e.g., the order of current and previous times and the primitive name.)
Pull Request: https://projects.blender.org/blender/blender/pulls/127163
Fixes a few issues with point clouds with HIPRT.
1. Crashing when building the BLAS due to an incorrect sized array.
2. A typo leading to all point cloud intersections being skipped.
3. A typo leading to some motion blurred point clouds rendering
as if they were stationary, or not rendering at all.
Pointclouds, with deformable motion blur, with BVH time steps set to >0
still do not render. Curves seem to have the same issue.
Ref #125086
Pull Request: https://projects.blender.org/blender/blender/pulls/125834
`atan2(0, 0)` is undefined on many platforms. To ensure consistent
result across platforms, we return `0` in this case.
Note only the behavior of the shader node `Artan2` is changed here.
During shading, we might still produce `atan2(0, 0)` internally and
cause different results across platforms, but that usually happens with
single samples and is not obvious, plus checking this condition all the
time is costly. If later we find out it's indeed necessary to change all
the invocation of `atan2(0, 0)`, we could change the wrapper functions
in `metal/compat.h` and `mtl_shader_defines.msl`.
Pull Request: https://projects.blender.org/blender/blender/pulls/126951
The kernel zeroing memory since we've added host memory fallback didn't
expect large inputs, so with these scenes, it was running into
"Provided range is out of integer limits. Pass
`-fno-sycl-id-queries-fit-in-int' to disable range check" error.
This kernel was used instead of memset to avoid some issues with the
free_memory queries not always being updated.
As we can't reproduce these with recent drivers, we now use memset,
which fixes rendering with BVH2.
Use a bounding sphere instead of the corners of a bounding box to
compute the subtended angle of a light tree node.
Using the corners of the bounding box was an underestimate in some
scenes, causing some light tree nodes being incorrectly skipped.
Using the subtended angle of a bounding sphere is an overestimate, but
it covers the entire node and would not skip any valid contribution,
and no other reliable algorithm to compute the minimal enclosing angle
is known to us.
We expect some increase in noise due to overestimation, but this has
not been observed yet, in our benchmark scenes only a difference in
noise is visible.
Thanks to Weizhen for the suggestion to use the bounding sphere.
Pull Request: https://projects.blender.org/blender/blender/pulls/126625
Add Metallic BSDF Node to the shader editor.
This node can primarily be used to create more realistic looking
metallic materials than the existing Glossy BSDF node.
This commit does not add any new closures to Cycles, it simply exposes
existing closures that were previous hard to access on their own.
- Exposes the F82 fresnel type that is currently used by the
metallic component of the Principled BSDF. Results should match
between the Metallic BSDF and Principled BSDF when using the same
settings.
- Exposes the Physical Conductor fresnel type that was previously
limited to custom OSL scripts. The Conductor fresnel type accepts
IOR and Extinction coefficients to define the appearance of the
material based off real life measurements.
EEVEE only supports the F82 fresnel type with internal code to convert
the the physical conductor inputs in to a colour format for F82,
which can lead to noticeable rendering differences with
some configurations.
Pull Request: https://projects.blender.org/blender/blender/pulls/114958
when tracing shadow ray through a volume and no hit is registered, we
consider the whole ray segment inside the volume.
However, no hit registered could also happen when the volume is
invisible to shadow ray. We should explicitly check this case and skip
rendering the volume segment instead.
Pull Request: https://projects.blender.org/blender/blender/pulls/126139
This patch improves the isotropic Gabor noise UI controls such that
variations happen in both directions of the base orientation, as opposed
to being biased in the positive direction only.
Thanks to Charlie Jolly for suggesting this improvement.
This patch optimizes the Gabor noise standard deviation estimation by
computing the upper limit of the integral as the frequency approaches
infinity, since the integral is mostly constant for the relevant
frequency range. The limits are 0.25 for the 2D case and 1 / 4 * sqrt2
for the 3D case.
This also improves normalization for low frequencies, possibly due to
the effect of windowing.
Thanks to Charlie Jolly for spotting the optimization.
Optimize the Gabor noise texture code with an early exit for points that
are further away from the kernel center. This was already done for the
kernel, but is now being done earlier before computing the weight, so
its computation is now skipped.
Thanks to Charlie Jolly for the suggestion.
Fixes missing intersections on straight 3D curves with the
Metal backend, with BVH2.
This issue could of manifested on other devices, but didn't seem to
in practice.
Pull Request: https://projects.blender.org/blender/blender/pulls/126197
The GPU packed state is a static check from the Cycles core perspective,
and it is disabled for non-Apple Silicon GPUs. However, the Metal kernel
always used packed integrator.
This change makes it so the Host and Device side checks for the Host CPU
are aligned, and that Device-side packed state check does not differ from
the Host side.
Pull Request: https://projects.blender.org/blender/blender/pulls/126082
This decreases BSDF_ROUGHNESS_SQ_THRESH so that the microfacet
roughness has a cutoff at much lower values and fixes a precision
issue in the bsdf_sample code that prevented this previously.
Pull Request: https://projects.blender.org/blender/blender/pulls/125919
I ran into this in a test scene - somehow the normalization here can result
in NaN (so presumably a zero vector). I don't think this has a notable
performance impact from some basic tests.
Pull Request: https://projects.blender.org/blender/blender/pulls/125930
the code snippet is supposed to compute the maximal `isect.t` in the
array, which is used to determine if subsequent intersections should be
added.
However, the previous implementation includes the old `isect.t` which is
going to be replaced, resulting an overestimation of `tmax_hits` and
thus missing closer intersections.
For BVH2, the issue is fixed by computing the `max_t` after a new entry
is inserted.
For Embree, the issue is fixed by finding the `second_largest_t` as well, and
compare that with the new insertion to find the new `max_t`.
Pull Request: https://projects.blender.org/blender/blender/pulls/125739
A phase function is normalized over the sphere, it is therefore
incorrect to sum two phase functions together when evaluating for NEE.
It should be a weighted sum with normalized weights, which, according to
`volume_shader_phase_pick()`, is `sample_weight / sum_sample_weight`.
Also corrects an error in `volume_shader_phase_pick()`.
Fix a NaN when rendering glossy materials that can appear due to a
division by zero in bsdf_D when rendering materials with low roughness.
Thank you to Weizhen for the fix after my incorrect
first attempt.
Pull Request: https://projects.blender.org/blender/blender/pulls/125756
Align Cycles SVM and EEVEE's rendering of the vector math node
in reflect mode with OSL when the normal vector is 0,0,0.
This is done by using safe_normalize rather than normalize on the
normal vector. Which also fixes a NaN in the reflect mode in this
specific configuration.
Pull Request: https://projects.blender.org/blender/blender/pulls/125688
This type of projection is often used e.g. in exhibitions that leverage big
curved screens.
Effectively, the frame is mapped onto a cylinder, with the x axis becoming the
longitude and y axis becoming the height.
Users can configure the min/max longitude, the min/max height and the radius of
the cylinder.
Co-authored-by: Lukas Stockner <lukas.stockner@freenet.de>
Pull Request: https://projects.blender.org/blender/blender/pulls/123046
After e3697710d0, if no UV map was found, then Cycles OSL would
generate UV coordinates for users. This was done to add UV coordinates
to lights, however it had the side effect of creating new UV
coordinates for other object types that don't have a UV map.
This lead to a rendering difference between OSL and SVM
when rendering meshes with no UV map, and objects with no
UV map, like curves.
This commit fixes this issue by adding a new "is_light" attribute to
Cycles OSL and using that to figure out if UV coordinates should be
generated for lights.
Pull Request: https://projects.blender.org/blender/blender/pulls/124673
The motivation is to be able to catch issues like #124705 early on,
by relying on asserts.
The not-so-obvious part of the change is the change in the order of
includes, which is needed for the types.h to have definition of the
kernel_assert().
Pull Request: https://projects.blender.org/blender/blender/pulls/124729
