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
Supports baking to object and tangent space.
Compatible with Cycles Vector Displacement node which has the
(tangent, normal, bitangent) convention.
The viewport situation is a bit confusing: seems that Eevee
does not handle vector displacement properly and rips all faces
apart. Cycles renders the displaced object correctly.
Not entirely happy with the UI, as displacement space does not
really belong to the Output, but so doesn't Low Resolution Mesh.
Perhaps the best would be to have a separate pass to revisit the
settings, and also make it more clear what the Low Resolution Mesh
actually does.
Pull Request: https://projects.blender.org/blender/blender/pulls/145014
Almost all settings were duplicated between BakeData and RenderData.
The only missing field was the bake type, which is stored as a custom
property in Cycles.
This change:
- Removes unused bake_samples and bake_biasdist.
- Migrates settings like bake_margin to BakeData.
- Switches multires baker to use bake_margin.
- Introduces bake type in the BakeData, the same way how it was
defined in RenderData::bake_mode.
Pull Request: https://projects.blender.org/blender/blender/pulls/144984
The main idea is to switch Bake from Multires from legacy DerivedMesh
to Subdiv. On the development side of things this change removes a lot
of code, also making it easier easier to rework CustomData and related
topics, without being pulled down by the DerivedMesh.
On the user level switch to Subdiv means:
- Much more closer handling of the multi-resolution data: the derived
mesh code was close, but not exactly the same when it comes to the
final look of mesh.
Other than less obvious cases (like old DerivedMesh approach doing
recursive subdivision instead of pushing subdivided vertices on the
limit surface) there are more obvious ones like difference in edge
creases, and non-supported vertex creases by the DerivedMesh.
- UV interpolation is done correctly now when baking to non-base level
(baking to multi-resolution level >= 1).
Previously in this case the old derived mesh interpolation was used
to interpolate face-varying data, which gives different results from
the OpenSubdiv interpolation.
- Ngon faces are properly supported now.
A possible remaining issue is the fact that getting normal from CCG
always uses smooth interpolation. Based on the code it always has been
the case, so while it is something to look into it might be considered
a separate topic to dig into.
`world_use_portal` is not needed anymore, now that we always add world
as object (b20b4218d5).
We now check if background light is enabled only in
`test_enabled_lights()`, depending on the sample settings.
Pull Request: https://projects.blender.org/blender/blender/pulls/144710
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
Currently, it was discovered that in the case of several different
Intel dGPUs being present in the system, the experimental L0 copy
optimization does not work correctly in the Intel Driver, which is
causing crashes in the driver and Blender application. So, to avoid
this situation and restore functionality on these platforms,
a workaround was added to disable this extension from being used if
such a configuration is detected. In the future, when this problem is
fully fixed in all Intel Drivers, this workaround can be removed from
the Blender source code to restore some performance that was lost on
configurations of several dGPUs because of this workaround.
Pull Request: https://projects.blender.org/blender/blender/pulls/144262
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.
Due to numerical issues this was creating many wrong self-overlapping.
It was necessary for skipping empty regions, but not any more with the
volume Octree approach
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
Modify shader update so we simplify the graphs first to determine the
kernel features, then load the kernels, and only then update data on the
device. This avoids errors due to mismatched kernels and shaders.
Pull Request: https://projects.blender.org/blender/blender/pulls/144238
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
Ever since the OptiX 8 update in Blender 4.5, the minimum GPU driver
requirements to use OptiX has increased to 535 or newer.
This commit update the minimum GPU driver requirement listed in the UI
to reflect this.
Pull Request: https://projects.blender.org/blender/blender/pulls/143917
