This was causing a warning when using OSL, since the OSL implementation
didn't implement the input.
Since the socket isn't really implemented on the Blender side anyways,
just get rid of it.
Also, the SVM code uses the shading normal while OSL used the geometric normal.
- 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
The recursive building has an early output, which could leave the node
without the requested child initialized, causing the access to the left
child to crash later on in the builder function.
Simply add an extra is-canceled check to avoid access of possibly
non-initialized tree structure.
Pull Request: https://projects.blender.org/blender/blender/pulls/112132
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
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
In the commonly used cycles headers, it's enough to include
much smaller <iosfwd> than the full <iostream>. While looking at it,
removed inclusion of some other headers from commonly used headers,
that seemed to not be needed.
Pull Request: https://projects.blender.org/blender/blender/pulls/111063
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
Both the `Math` node and the `Vector Math` currently only explicitly
support modulo using truncated division which is oftentimes not the
type of modulo desired as it behaves differently for negative numbers
and positive numbers.
Floored Modulo can be created by either using the `Wrap` operation or
a combination of multiple `Math` nodes. However both methods obfuscate
the actual intend of the artist and the math operation that is actually
used.
This patch adds modulo using floored division to the scalar `Math` node,
explicitly stating the intended math operation and renames the already
existing `"Modulo"` operation to `"Truncated Modulo"` to avoid confusion.
Only the ui name is changed, so this should not break compatibility.
Pull Request: https://projects.blender.org/blender/blender/pulls/110728
The current core was only detecting sRGB transform when it is defined
as sRGB->Linear using srgb.spi1d. If it is defined as an inverse of
Linear->sRGB using srgb_inv.spi1d, or as an analytical formula using
ExponentWithLinearTransform then the code did not detect the color
as sRGB on anything by Apple Silicon platform.
The naming of the checks could be improved to make it more clear that
the check is only used to allow lossless access to 8bit sRGB textures.
Ref #110685
Pull Request: https://projects.blender.org/blender/blender/pulls/110889
This replaces the Sheen model used in the Principled BSDF with the
model from #108869 that is already used in the Sheen BSDF now.
The three notable differences are:
- At full intensity (Sheen = 1.0), the new model is significantly
stronger than the old one. For existing files, the intensity is
adjusted to keep the overall look similar.
- The Sheen Tint input is now a color input, instead of the
previous blend factor between white and the base color.
- There is now a Sheen roughness control, which can be used to
tweak the look between velvet-like and dust-like.
Pull Request: https://projects.blender.org/blender/blender/pulls/109949
This was already unsupported in combination with Multiscattering GGX,
prevented the Principled BSDF from using microfaced-based Fresnel for
Glass materials, and would have made future improvements even trickier.
Pull Request: https://projects.blender.org/blender/blender/pulls/109950
this option was already unselectable in the UI, and is treated as GGX
with zero roughness. Upon building the shader graph, we only convert a
closure to `SHARP` when option Filter Glossy is not used and the
roughness is below certain threshold. The benefit is that we can avoid
calling `bsdf_eval()` or return earlier in some cases, but the thresholds
vary across files.
This patch removes `SHARP` closures altogether, and checks if the
roughness value is below a global threshold `BSDF_ROUGHNESS_THRESH`
after blurring, in which case the flag `SD_BSDF_HAS_EVAL` is not set.
The global threshold is set to be `5e-7f` because threshold smaller than
that seems to have caused problem in the past (c6aa0217ac). Also removes
a bunch of functions, variables and arguments that were only there
because we converted closures under certain conditions.
Pull Request: https://projects.blender.org/blender/blender/pulls/109902
Using area-preserving mapping from cone to disk. Has somewhat distortion
near 90°.
The texture rotates with the transformation of the light object, can
have negative and non-uniform scaling.
Pull Request: https://projects.blender.org/blender/blender/pulls/109842
* Use pi factor to convert between radiant flux and intensity
* Mark lights as normalized on export
* Add spot light export support
* Add treatAsPoint support for import and export
* Empirically match normalized distant light
* Fix wrong unnormalized point/sphere/disk light unit in Cycles
Overall it should be much closer now for all light types. Point and distant
light units are inconsistent between renderers, so not possible to match
everything there.
Ref #109404
Pull Request: https://projects.blender.org/blender/blender/pulls/109795
This fixes the issue described in https://projects.blender.org/blender/blender/issues/108957.
Instead of modeling distant lights like a disk light at infinity, it models them as cones. This way, the radiance is constant across the entire range of directions that it covers.
For smaller angles, the difference is very subtle, but for very large angles it becomes obvious (here's the file from #108957, the angle is 179°):
| Old | New |
| - | - |
|  |  |
One notable detail is the sampling method: Using `sample_uniform_cone` can increase noise, since the sampling method no longer preserves the stratification of the samples. This is visible in the "light tree multi distant" test scene.
Turns out we can do better, and after a bit of testing I found a way to adapt the concentric Shirley mapping to uniform cone sampling. I hope the comment explains the logic behind it reasonably well.
Here's the result, note that even the noise distribution is the same when using the new sampling:
| Method | Old | New, basic sampling | New, concentric sampling |
| - | - |- | - |
| Image |  |  |  |
| Render time (at higher spp)| 9.03sec | 8.79sec | 8.96sec |
I'm not sure if I got the `light->normalized` handling right, since I don't really know what the expectation from Hydra is here.
Co-authored-by: Weizhen Huang <weizhen@blender.org>
Pull Request: https://projects.blender.org/blender/blender/pulls/108996
The spotlight is now treated as a sphere instead of a view-aligned disk.
The implementation remains almost identical to that of a point light,
except for the spotlight attenuation and spot blend. There is no
attenuation inside the sphere. Ref #108505
Other changes include:
## Sampling
Instead of sampling the disk area, the new implementation samples either
the cone of the visible portion on the sphere or the spread cone, based
on which cone has a smaller solid angle. This reduces noise when the
spotlight has a large radius and a small spread angle.
| Before | After |
| -- | -- |
||
## Texture
Spot light can now project texture using UV coordinates.
<video src="/attachments/6db989d2-7a3c-4b41-9340-f5690d48c4fb"
title="spot_light_texture.mp4" controls></video>
## Normalization
Previously, the normalization factor for the spotlight was \(\pi r^2\),
the area of a disk. This factor has been adjusted to \(4\pi r^2\) to
account for the surface area of a sphere. This change also affects point
light since they share the same kernel type.
## Versioning
Some pipeline uses the `Normal` socket of the Texture Coordinate node for
projection, because `ls->Ng` was set to the incoming direction at the
current shading point. Now that `ls->Ng` corresponds to the normal
direction of a point on the sphere (except when the radius is zero),
we replace these nodes with a combination of the Geometry shader node
and the Vector Transform node, which gives the same result as before.
Example file see https://archive.blender.org/developer/T93676
Pull Request: https://projects.blender.org/blender/blender/pulls/109329
for energy preservation and better compatibility with other renderes. Ref: #108505
Point light now behaves the same as a spherical mesh light with the same overall energy (scaling from emission strength to power is \(4\pi^2R^2\)).
# Cycles
## Comparison
| Mesh Light | This patch | Previous behavior |
| -------- | -------- | -------- |
|  |  |  |
The behavior stays the same when `radius = 0`.
| This patch | Previous behavior |
| -------- | -------- |
|  |  |
No obvious performance change observed.
## Sampling
When shading point lies outside the sphere, sample the spanned solid angle uniformly.
When shading point lies inside the sphere, sample spherical direction uniformly when inside volume or the surface is transmissive, otherwise sample cosine-weighted upper hemisphere.
## Light Tree
When shading point lies outside the sphere, treat as a disk light spanning the same solid angle.
When shading point lies inside the sphere, it behaves like a background light, with estimated outgoing radiance
\[L_o=\int f_aL_i\cos\theta_i\mathrm{d}\omega_i=\int f_a\frac{E}{\pi r^2}\cos\theta_i\mathrm{d}\omega_i\approx f_a \frac{E}{r^2}\],
with \(f_a\) being the BSDF and \(E\) `measure.energy` in `light_tree.cpp`.
The importance calculation for `LIGHT_POINT` is
\[L_o=f_a E\cos\theta_i\frac{\cos\theta}{d^2}\].
Consider `min_importance = 0` because maximal incidence angle is \(\pi\), we could substitute \(d^2\) with \(\frac{r^2}{2}\) so the averaged outgoing radiance is \(f_a \frac{E}{r^2}\).
This only holds for non-transmissive surface, but should be fine to use in volume.
# EEVEE
When shading point lies outside the sphere, the sphere light is equivalent to a disk light spanning the same solid angle. The sine of the new half-angle is the tangent of the previous half-angle.
When shading point lies inside the sphere, integrating over the cosine-weighted hemisphere gives 1.0.
## Comparison with Cycles
The plane is diffuse, the blue sphere has specular component.
| Before | |After ||
|---|--|--|--|
|Cycles|EEVEE|Cycles|EEVEE|
|||||
Pull Request: https://projects.blender.org/blender/blender/pulls/108506
Somehow the implementation for the main function to load point clouds
data was missing although everything else to support point clouds was
there. Compilers were more than happy to convert the IPointsSchema to
another schema type for the compilation to succeed, and the crash
occurs because the points schema does not contain the same data as the
compiler's chosen schema (in this case an ICurvesSchema).
Another crash was found due to the radius array not being properly
initialized and left with a size of 0, when Cycles expects a full array.
