The SVM logic was changed a while ago to not adjust normals for curves,
but this wasn't applied to OSL as well, causing differences in SVM/OSL renders.
This has two main advantages: First, it allows to get rid of the extra closure
since the remaining float can just be moved to the main closure allocation.
Second, previously sd->N was completely unused and therefore unintialized,
which ended up causing issues for the Normal render pass.
When evaluating emission, no closures can be allocated, so the existing code
would end up returning albedo 1.0, which then caused the layering code to set
the weight of lower layers to zero.
SVM doesn't do this, neither does the OSL testrender from what I can tell, and
in other cases we already handle the inversion on the OSL side if needed.
This patch updates the experimental MetalRT code path to use new [curve primitives](https://developer.apple.com/videos/play/wwdc2023/10128/) which were recently added in macOS 14. This replaces the previous custom box intersection implementation, allowing the driver to better optimise curve acceleration structures for the GPU. On existing hardware, this can speed up MetalRT renders by up to 40% for scenes that use hair / curve primitives extensively.
The MetalRT option will only be available on macOS >= 14, and requires Xcode >= 15 to build (otherwise the option will be compiled out).
Authored by Marco Giordano, Michael Jones, and Jason Fielder
---
Before / after render times (M1 Max MacBook Pro, macOS 14 beta, MetalRT enabled):
```
Custom box intersection MetalRT curve primitives Speedup
fishy_cat 111.5 80.5 1.39
koro 114.4 86.7 1.32
sinosauropteryx 291.8 279.2 1.05
spring 142.3 142.2 1.00
victor 442.7 347.7 1.27
```
---
Pull Request: https://projects.blender.org/blender/blender/pulls/111795
- Changes defaults from Emission Color 0.0, Emission Strength 1.0 to be the
other way around (Color 1.0, Strength 0.0), suggested by @brecht
- Makes emission component occluded by sheen and coat
(to simulate e.g. dust-covered light sources)
- Moves transparency into the Principled SVM/OSL node, to allow for future
support for e.g. transparent shadows in thin sheet mode.
Note that there are optimization opportunities here (mostly skipping the
non-transparent components for transparent shadow evaluation, and skipping
the parts that don't affect emission for light evaluation), but I have a
separate point for those in the Principled V2 planning since there's some
other optimization topics as well.
Co-authored-by: Weizhen Huang <weizhen@blender.org>
Pull Request: https://projects.blender.org/blender/blender/pulls/111155
Previously, the Principled BSDF used the Subsurface input to scale the radius.
When it was zero, it used a diffuse closure, otherwise a subsurface closure.
This sort of scaling input makes sense, but it should be specified in distance
units, rather than a 0..1 factor, so this commit changes the unit and renames
the input to Subsurface Scale.
Additionally, it adds support for mixing diffuse and subsurface components.
This is part of e.g. the OpenPBR spec, and the logic behind it is to support
modeling e.g. dirt or paint on top of skin. Before, materials would be either
fully diffuse (radius=0) or fully subsurface.
For typical materials, this mixing factor will be either zero or one
(just like metallic or transmission), but supporting fractional inputs makes
sense for e.g. smooth transitions at boundaries.
Another change is that there is no separate Subsurface Color anymore - before,
this was mixed with the Base Color using the Subsurface input as the factor,
but this was not really useful since that input was generally very small.
And finally, the handling of how the path enters the material for random walk
subsurface scattering is changed. Before, this always used lambertian (diffuse)
transmission, but this caused some problems, like overly white edges.
Instead, two different methods are now used, depending on the selected mode.
In Fixed Radius mode, the code assumes a simple medium boundary, and performs
refraction into the material using the main Roughness and IOR inputs.
Meanwhile, when not using Fixed Radius, the code assumes a more complex
boundary (as typically found on organic materials, e.g. skin), so the entry
bounce has a 50/50 chance of being either diffuse transmission or refraction
using the separate Subsurface IOR input and a fixed roughness of 1.
Credit for this method goes to Christophe Hery.
Pull Request: https://projects.blender.org/blender/blender/pulls/110989
- Adds tint control, which simulates volumetric absorption inside the coating.
This results in angle-dependent saturation and affects all underlying layers
(diffuse, subsurface, metallic, transmission). It provides a physically-based
alternative to ad-hoc effects such as tinted specular highlights.
- Renames the component from "Clearcoat" to "Coat", since it's no longer
necessarily clear now. This matches naming in e.g. other renderers or OpenPBR.
- Adds an explicit Coat IOR input, in preparation for future smarter IOR logic
around the interaction between Coat and main IOR. This used to be hardcoded
to 1.5.
- Removes hardcoded 0.25 weight multiplier, and adds versioning code to update
existing files accordingly. OBJ import/export still applies the factor.
- Replaces the GTR1 microfacet component with regular GGX. This removes a corner
case in the Microfacet code, solves #53038, and makes us more consistent with
other standard surface shaders. The original Disney BSDF used GTR1, but it
doesn't appear that it caught on in the industry.
Co-authored-by: Weizhen Huang <weizhen@blender.org>
Pull Request: https://projects.blender.org/blender/blender/pulls/110993
was mixing real geometry normal, smoothed geometry normal and
bump-mapped normal.
Use `(sd->type & PRIMITIVE_CURVE) ? sc->N : sd->Ng` consistently instead.
We already have two other functions doing very much the same thing.
`bsdf_microfacet_sample()` seems to be the only place where this
function was used; there we always sample visible normals, so the extra
`inside` check is not needed.
1. move early-out logic even earlier
2. reduced the scope of some variables
3. return `label` at the end of `bsdf_microfacet_sample()`. Return
`LABEL_NONE` in the invalid case. The previous distinction was
unnecessary because samples with zero contribution are assigned with
`LABEL_NONE` in `integrate_surface_bsdf_bssrdf_bounce()` anyway.
the motivation was to give closures with low weight a higher pdf to pick
at the first bounce, in case the next interaction has high contribution.
However, there are several issues:
1. this is too much fine-tuned for a specific case, and only works well
when there is a strong contribution after reflection and very little
contribution after the transmission;
2. the logic in `bsdf_microfacet.h` was added when merging reflection
and refraction into a glass closure, since then it doesn't even work
well in the above case when mixed with other closures;
3. The behavior is inconsistent in `bsdf_microfacet_eval()` and
`bsdf_microfacet_sample()`;
4. such cases should be handled by more modern and more general methods
such as path guiding and denoiser;
5. it makes the code flow harder to follow
Delete this trick for now to pick the closures solely based on their
`sample_weight`. Can be added back (with proper fix in
`bsdf_microfacet`) if indeed necessary.
The API for the kernels library is defined, there is no need to
export more than that. This change only affects linux since hidden
visiblity is the default on Windows.
Curve normal is not available in legacy particle hair system. Construct
a local coordinate system instead of using a fixed normal direction [1,
0, 0] to avoid black appearance.
Use the common BVH utilities header for this.
Added a special type qualifier ccl_ray_data which is defined to ccl_private
for all platforms but Metal. On Metal it is defined to ray_data.
The tricky part is that the BVH utilities are wrapped into the Metal context
class. In some of the BVH functions the context has been already constructed,
but it wasn't done in all the callbacks.
From a quick render tests of the Junkshop benchmark scene there is no render
time difference,
No functional changes are expected.
Pull Request: https://projects.blender.org/blender/blender/pulls/111967
Cycles oneAPI kernel library was compiled using -ffast-math. The current
version of Clang makes it link to crtfastmath.o in that case, bringing a
static constructor that does set the FTZ/DAZ bits in MXCSR for the whole
program, leading to unwanted behavior with other components.
Instead of -ffast-math, we switch to a safer subset of compile flags.
Pull Request: https://projects.blender.org/blender/blender/pulls/111708
based on concentric disk mapping.
Concentric disk mapping was already present, but not used everywhere.
Now `sample_cos_hemisphere()`, `sample_uniform_hemisphere()`, and
`sample_uniform_cone()` use concentric disk mapping.
This changes the noise in many test images.
Pull Request: https://projects.blender.org/blender/blender/pulls/109774
This reverts commit 206ab6437b.
Seems that the illegal address error should be covered elsewhere, but it's not directly
clear where. Revert the commit for further investigation.
Discovered during an investigation into #111277
in rare situations (E.G. When normals are NaN), an emitter
won't be selected as part of `light_tree_cluster_select_emitter()`
and as a result of that, an `emitter_index` of `-1` is passed to
`kernel_data_fetch(light_tree_emitters, emitter_index)` resulting in
an "illegal address" error on some devices.
Pull Request: https://projects.blender.org/blender/blender/pulls/111292
Fixes NaN in Vector Displacement node caused by the normalization of
0, 0, 0 vectors.
This fixes both visual rendering issues and an "illegal address" error
on the GPU. The "illegal address" error came from the Light Tree
Sampling code not handling the NaN normals well, leading to weird code
paths being taken, eventually leading to a kernel_assert and a
user facing illegal address error.
Pull Request: https://projects.blender.org/blender/blender/pulls/111294
Implements the paper [A Microfacet-based Hair Scattering
Model](https://onlinelibrary.wiley.com/doi/full/10.1111/cgf.14588) by
Weizhen Huang, Matthias B. Hullin and Johannes Hanika.
### Features:
- This is a far-field model, as opposed to the previous near-field
Principled Hair BSDF model. The hair is expected to be less noisy, but
lower roughness values takes longer to render due to numerical
integration along the hair width. The hair also appears to be flat when
viewed up-close.
- The longitudinal width of the scattering lobe differs along the
azimuth, providing a higher contrast compared to the evenly spread
scattering in the near-field Principled Hair BSDF model. For a more
detailed comparison, please refer to the original paper.
- Supports elliptical cross-sections, adding more realism as human hairs
are usually elliptical. The orientation of the cross-section is aligned
with the curve normal, which can be adjusted using geometry nodes.
Default is minimal twist. During sampling, light rays that hit outside
the hair width will continue propogating as if the material is
transparent.
- There is non-physical modulation factors for the first three
lobes (Reflection, Transmission, Secondary Reflection).
### Missing:
- A good default for cross-section orientation. There was an
attempt (9039f76928) to default the orientation to align with the curve
normal in the mathematical sense, but the stability (when animated) is
unclear and it would be a hassle to generalise to all curve types. After
the model is in main, we could experiment with the geometry nodes team
to see what works the best as a default.
Co-authored-by: Lukas Stockner <lukas.stockner@freenet.de>
Pull Request: https://projects.blender.org/blender/blender/pulls/105600
The `Find*.cmake` modules originally used uppercase commands to match
CMake's own conventions. Since then CMake uses lower-case and even
within our own find modules, using all uppercase wasn't done
consistently. Opt for lowercase everywhere.
This PR adds the Lacunarity and Normalize inputs to the Noise node
similar to the Voronoi node.
The Lacunarity input controls the scale factor by which each
successive Perlin noise octave is scaled. Which was previously hard
coded to a factor of 2.
The Noise node normalizes its output to the [0, 1] range by default.
The Normalize option makes it possible for the user to disable that.
To keep the behavior consistent with past versions it is enabled by
default.
To make the aforementioned normalization control easer to implement,
the fractal noise code now accumulates signed noise and remaps the
final sum, as opposed to accumulating positive [0, 1] noise.
Pull Request: https://projects.blender.org/blender/blender/pulls/110839
Overall, this commit reworks the component layering in the Principled BSDF
in order to ensure that energy is preserved and conserved.
This includes:
- Implementing support for the OSL `layer()` function
- Implementing albedo estimation for some of the closures for layering purposes
- The specular layer that the Principled BSDF uses has a proper tabulated
albedo lookup, the others are still approximations
- Removing the custom "Principled Diffuse" and replacing it with the classic
lambertian Diffuse, since the layering logic takes care of energy now
- Making the merallic component independent of the IOR
Note that this changes the look of the Principled BSDF noticeably in some
cases, but that's needed, since the cases where it looks different are the
ones that strongly violate energy conservation (mostly grazing reflections
with strong Specular).
Pull Request: https://projects.blender.org/blender/blender/pulls/110864
Many calls to add_check_c_compiler_flag add_check_cxx_compiler_flag
resulted in over long lines & visual noise. Replace with a function that
takes multiple (cache_var flag) pairs to reduce duplication.
