The one-sample Monte Carlo estimator of the radiative transfer equation
is
<L> = T(t) / p(t) * (L_e + σ_s * L_s + σ_n * L),
Which means we can also use another p(t) than majorant * exp(-majorant * t)
for sampling the distance. Thus, we use the baked σ_max for distance
sampling, but adjust the majorant when we encounter a density that is
larger than σ_max.
Note that this is not really unbiased because such scaling is not always
applied, but seems to work well in practice when the majorant is
reasonable.
Pull Request: https://projects.blender.org/blender/blender/pulls/146589
This implements a basic render time pass,
using HW-based counters to minimize render time impact.
x86-64 uses the TSC instruction for timing, while ARM64 uses the cntvct_el0
register. In theory TSC is not always super reliable (e.g. old CPUs had it tied
to their current clock rate), but for somewhat recent CPU models it should
be fine. If neither is available, it falls back to `std::chrono::steady_clock`,
which should still be very fast.
The output is in milliseconds of CPU-time per pixel.
Pull Request: https://projects.blender.org/blender/blender/pulls/125933
On its own, the main functionality of the Radial Tiling node
is the ability to divide a 2D Cartesian coordinate system into
as many radial segments as specified by the "Segments" input.
Each segment has its own affinely transformed coordinate system,
provided through the "Segment Coordinates" output, which can be
used to tile textures in a radially symmetric manner.
Additionally, a unique index is provided for every segment through
the "Segment ID" output, the width of each segment at Y-coordinate
of the "Segment Coordinates" output without normalization = 0 is
provided through the "Segment Width" output and the rotation value
of the affine transformation of the coordinate system of each segment
is provided through the "Segment Rotation" output.
The roundness of the coordinate lines of the "Segment Coordinates"
output can be controlled through the "Roundness" inputs.
This can be used to make the coordinate systems of the segments
a mix of Cartesian and polar coordinates.
Lastly, the lines of points of the "Segment Coordinates" output with
constant Y-coordinates have the shape of polygon with rounded corners,
which can be used to procedurally create rounded polygons.
Pull Request: https://projects.blender.org/blender/blender/pulls/127711
These are causing quite a big difference in existing files, which is not
easy to address in versioning. Since the goal of removing this was to
simplify things for us and that's not the case, just revert this change.
This reverts commit ab21755aaf.
Ref #139923
Pull Request: https://projects.blender.org/blender/blender/pulls/146336
For some reason, the `underwater_caustics` test was failing on Metal
after #140480 even though that test doesn't use the Sky Texture.
After messing with the file for a while, going back to the previous version
and adding the changes back one at a time, I've now arrived at a version
that behaves the same way as the #140480 version without breaking the test.
No idea what is the underlying issue, but we've had problems with the MNEE
kernels before so maybe just a compiler thing.
Pull Request: https://projects.blender.org/blender/blender/pulls/146335
This mode is based on the same athmospheric model as the previous one, but now
also accounts for multiple scattering and reflections from the ground.
This increases the accuracy, especially at low elevations.
Also renames some options for consistency:
- The previous "Nishita" model is now "Single Scattering"
- "Dust" is now "Aerosols"
- Default altitude is now 100m.
Co-authored-by: Lukas Stockner <lukas@lukasstockner.de>
Pull Request: https://projects.blender.org/blender/blender/pulls/140480
Metal-RT implementation for curve intersect has an additional self
intersection check happening in curve_ribbon_accept(). It is done
for all curve types that has PRIMITIVE_CURVE_RIBBON bit set on them,
including Thick Linear curves. However, the logic in the function is
hardcoded to handle flat ribbon curves with the Catmull Rom basis.
This change makes it so curve_ribbon_accept() is only called for the
ribbon curve type, not when type has ribbon bit set.
Additionally, other places where curve type was checked as a bitmask
were fixed.
Ref #146072
Pull Request: https://projects.blender.org/blender/blender/pulls/146140
When shadow linking is enabled, `intersect_dedicated_light` is scheduled even
if the `PATH_RAY_SUBSURFACE` flag is set. This checks the flag and schedules
`intersect_subsurface` instead.
Pull Request: https://projects.blender.org/blender/blender/pulls/145621
These don't really work as scene linear with sRGB transfer function for e.g.
ACEScg, there are not enough bits. If you want wide gamut you need to use
float colors.
Pull Request: https://projects.blender.org/blender/blender/pulls/145763
Experiments have shown that the OptiX denoiser performs best when
operating on images that have their origin at the top-left corner,
while Blender renders with the origin at the bottom-left corner.
Simply flipping the image vertically before and after denoising is a
relatively trivial operation, so this patch introduces this as an
additional preprocessing and postprocessing step for denoising when the
OptiX denoiser is used. Additionally, this patch also removes an unused
helper function, now that OptiX 8.0 is the minimum.
Pull Request: https://projects.blender.org/blender/blender/pulls/145358
The compiler in the CUDA 13 toolkit dropped support for Maxwell, Pascal and Volta architectures (sm_5X, sm_6X and sm_70), which affects both CUDA and OptiX kernel compilation for Cycles. This patch makes it so building CUDA kernel binaries for those architectures are skipped when CUDA 13 is used, but it will still build them if there is a CUDA 11 toolkit available (e.g. on buildbot), like how things are handled for other architectures. The OptiX PTX kernel is compiled with the minimum architecture available (compute_75 with CUDA 13, compute_50 with previous CUDA versions).
In addition, loading the PTX kernel after initializing OptiX version 9.0 would fail with a OPTIX_ERROR_INVALID_FUNCTION_USE, due to the use of "optixTrace" within direct callables (as part of the AO and bevel SVM nodes). Starting with OptiX 9.0 this is no longer allowed, rather one has to use "optixTraverse" in those cases. This patch thus changes the affected intersection routines to use "optixTraverse". As a side effect it also simplifies the `scene_intersect_shadow` function, which no longer invokes the closest hit program, and can just quickly return hit status. The minimum OptiX version Cycles requires is already 8.0, which supports "optixTraverse", so it can just be applied always.
Finally, this patch also adds the `--split-compile=0` argument to nvcc when available, which tells the compiler to internally split the module into pieces that can be processed in parallel on multiple threads (the `=0` notes to use as many threads as there are CPU cores), which can greatly improving compile times, while not making compromises on performance.
Pull Request: https://projects.blender.org/blender/blender/pulls/145130
This re-applies pull request #140671, but with a fix for #144713 where the
non-pointer part of IntegratorStateGPU was not initialized.
This PR is a more extensive follow on from #123551 (removal of AMD and Intel
GPU support).
All supported Apple GPUs have Metal 3 and tier 2 argument buffer support.
The invariant resource properties `gpuAddress` and `gpuResourceID` can be
written directly into GPU structs once at setup time rather than once per
dispatch. More background info can be found in this article:
https://developer.apple.com/documentation/metal/improving-cpu-performance-by-using-argument-buffers?language=objc
Code changes:
- All code relating to `MTLArgumentEncoder` is removed
- `KernelParamsMetal` updates are directly written into
`id<MTLBuffer> launch_params_buffer` which is used for the "static"
dispatch arguments
- Dynamic dispatch arguments are small enough to be encoded using the
`MTLComputeCommandEncoder.setBytes` function, eliminating the need for
cycling temporary arg buffers
Fix#144713
Co-authored-by: Brecht Van Lommel <brecht@noreply.localhost>
Pull Request: https://projects.blender.org/blender/blender/pulls/145175
Blender grid rendering interprets voxel transforms in such a way that the voxel
values are located at the center of a voxel. This is inconsistent with OpenVDB
where the values are located at the lower corners for the purpose or sampling
and related algorithms.
While it is possible to offset grids when communicating with the OpenVDB
library, this is also error-prone and does not add any major advantage.
Every time a grid is passed to OpenVDB we currently have to take care to
transform by half a voxel to ensure correct sampling weights are used that match
the density displayed by the viewport rendering.
This patch changes volume grid generation, conversion, and rendering code so
that grid transforms match the corner-located values in OpenVDB.
- The volume primitive cube node aligns the grid transform with the location of
the first value, which is now also the same as min/max bounds input of the
node.
- Mesh<->Grid conversion does no longer require offsetting grid transform and
mesh vertices respectively by 0.5 voxels.
- Texture space for viewport rendering is offset by half a voxel, so that it
covers the same area as before and voxel centers remain at the same texture
space locations.
Co-authored-by: Brecht Van Lommel <brecht@blender.org>
Pull Request: https://projects.blender.org/blender/blender/pulls/138449
It works with the beta we are using to build Blender 4.5, but the official
release is a bit different. This fix was tested to work with OSL 1.14.7.
Thanks to Paul Zander for finding the OSL commit that lead to this.
Pull Request: https://projects.blender.org/blender/blender/pulls/144715
It has ~1.2x speed-up on CPU and ~1.5x speed-up on GPU (tested on Metal
M2 Ultra).
Individual samples are noisier, but equal time renders are mostly
better.
Note that volume emission renders differently than before.
Pull Request: https://projects.blender.org/blender/blender/pulls/144451
Guide the probability to scatter in or transmit through the volume.
Only applied for primary rays.
Co-authored-by: Brecht Van Lommel <brecht@blender.org>
The distance sampling is mostly based on weighted delta tracking from
[Monte Carlo Methods for Volumetric Light Transport Simulation]
(http://iliyan.com/publications/VolumeSTAR/VolumeSTAR_EG2018.pdf).
The recursive Monte Carlo estimation of the Radiative Transfer Equation is
\[\langle L \rangle=\frac{\bar T(x\rightarrow y)}{\bar p(x\rightarrow
y)}(L_e+\sigma_s L_s + \sigma_n L).\]
where \(\bar T(x\rightarrow y) = e^{-\bar\sigma\Vert x-y\Vert}\) is the
majorant transmittance between points \(x\) and \(y\), \(p(x\rightarrow
y) = \bar\sigma e^{-\bar\sigma\Vert x-y\Vert}\) is the probability of
sampling point \(y\) from point \(x\) following exponential
distribution.
At each recursive step, we randomly pick one of the two events
proportional to their weights:
* If \(\xi < \frac{\sigma_s}{\sigma_s+\vert\sigma_n\vert}\), we sample
scatter event and evaluate \(L_s\).
* Otherwise, no real collision happens and we continue the recursive
process.
The emission \(L_e\) is evaluated at each step.
This also removes some unused volume settings from the UI:
* "Max Steps" is removed, because the step size is automatically specified
by the volume octree. There is a hard-coded threshold `VOLUME_MAX_STEPS`
to prevent numerical issues.
* "Homogeneous" is automatically detected during density evaluation
An option "Unbiased" is added to the UI. When enabled, densities above
the majorant are clamped.
Since we sample the same light for distance sampling and equiangular
sampling, the sample is invalid anyway, so just avoid sampling direct
light for distance sampling too.
This fits better with the way normal and displacement maps are typically
combined. Previously there was a mixing of displaced normal and undisplaced
tangent, which was broken behavior.
Additionally, to undisplaced_N and undisplaced_tangent attributes must now
always be used to get undisplaced coordinates. The regular N and tangent
attributes now always include displacement.
Ref #142022
Pull Request: https://projects.blender.org/blender/blender/pulls/143109
The Principled BSDF has a ton of inputs, and the previous SVM code just always
allocated stack space for all of them. This results in a ton of additional
NODE_VALUE_x SVM nodes, which slow down execution.
However, this is not really needed for two reasons:
- First, many inputs are only used consitionally. For example, if the
subsurface weight is zero, none of the other subsurface inputs are used.
- Many of the inputs have a "usual" value that they will have in most
materials, so if they happen to have that value we can just indicate that
by not allocating space for them.
This is a bit similar to the standard "pack the fixed value and provide
a stack offset if there's a link" pattern, except that the fixed value
is a constant in the code and we allocate a NODE_VALUE_x if a different
fixed value is used.
Therefore, this PR re-implements the parameter packing in a more efficient way:
- If we can determine that a component is disabled, all conditional inputs are
disconnected (to avoid generating upstream nodes).
- If we can determine that a component is disabled, we skip allocating all
conditional inputs on the stack.
- The inputs for which a reasonable "usual" value exists are changed to
respect that, and to only be allocated if they differ.
- param1 and param2 (which are fixed-value-packed as on all BSDF nodes) are
used to store IOR and roughness, which have a decent chance to be fixed
values.
- The parameter packing is more aggressive about using uchar4, which allows
to get rid of two SVM nodes while still storing the same inputs.
The result is a considerable speedup in scenes that make heavy use of the
Principled BSDF:
| Scene | CPU speedup | OptiX speedup |
| --- | --- | --- |
| attic | 5% | 9% |
| bistro | 5% | 8% |
| junkshop | 5% | 10% |
| monster | 3% | 4% |
| spring | 1% | 6% |
Pull Request: https://projects.blender.org/blender/blender/pulls/143910
This PR adds a new `fresnel_conductor_polarized` function, which calculates reflectance and phase shift (if requested) for both parallel and perpendicular polarized light. This is needed for applying thin film iridescence to conductors (see !141131).
For consistency, this PR also makes `fresnel_conductor` call `fresnel_conductor_polarized` instead of using a fast approximation of the Fresnel equations that is inaccurate at lower n and k values. This will change the output of some Metallic BSDF renders using Physical Conductor and prevent discrepancies when enabling thin film iridescence.
I didn't do any rigorous performance testing, but from timing the functions outside of Blender, `fresnel_conductor_polarized` is significantly slower than the approximation, between 1.5-3x depending on the compiler. This makes sense because it has three square roots and the approximation has none. In some informal tests with metallic_multiggx_physical.blend modified to have more spheres, the new renders took around 1-2% longer on both CPU and GPU.
There are some avoidable inefficiencies in this approach of just calling `fresnel_conductor_polarized`:
- one of the three square roots could be saved since `fresnel_conductor` never needs the phase shift and there are simplifications possible when only calculating the reflectance
- there are several unnecessary multiplications by 1.0 since `fresnel_conductor` uses relative IOR and `fresnel_conductor_polarized` doesn't, though those could get optimized out if inlined
Pull Request: https://projects.blender.org/blender/blender/pulls/143903
This replaces `stack_assign` with `stack_assign_if_linked`, which should save a few SVM nodes for constant parameters.
Running benchmarks (all scenes in the benchmark repo, 3 runs, median value for each) shows 1.0% improvement on CPU and 1.5% on OptiX. Not huge, but fairly (all between -0.2% and 3.0%).
Pull Request: https://projects.blender.org/blender/blender/pulls/143404
This change puts all the block size macros in the same common header, so
they can be included in host side code without needing to also include
the kernels that are defined in the device headers that contained these
values.
This change also removes a magic number used to enqueue a kernel, which
happened to agree with the GPU_PARALLEL_SORT_BLOCK_SIZE macro.
Pull Request: https://projects.blender.org/blender/blender/pulls/143646
