since the color is applied both at entry and exit, using the square root
of the color would make the perceived color closer to the desired one.
This also makes the transition smoother when changing the `Transmission`
value in the UI, and matches the behaviour of EEVEE.
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.
- 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
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
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
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
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
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 is only used as temporary state while evaluating SVM nodes,
there's no point in storing it in the ShaderData for later.
Since ShaderData size is relevant for GPU performance, we should
save the space and only keep it where needed.
Pull Request: https://projects.blender.org/blender/blender/pulls/110366
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
Previously the normal strength linearly interpolated and extrapolated
the normal in world space. Instead do it in tangent space, in a way
that ensure the normal remains above the surface and valid.
Pull Request: https://projects.blender.org/blender/blender/pulls/109763
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
The Voronoi distance output is clamped at 8, which is apparent for distance
metrics like Minkowski with low exponents.
This patch fixes that by setting the initial distance of the search loop to
FLT_MAX instead of 8. And for the Smooth variant of F1, the "h" parameter is set
to 1 for the first iteration using a signal value, effectively ignoring the
initial distance and using the computed distance at the first iteration instead.
Pull Request: https://projects.blender.org/blender/blender/pulls/109286
The Voronoi Smooth F1 mode breaks when the Smoothness is 0 for OSL. This is
due to a zero division in the shader.
To fix this, standard F1 is used when Smoothness is 0.
Pull Request: https://projects.blender.org/blender/blender/pulls/109255
Fractal noise is the idea of evaluating the same noise function multiple times with
different input parameters on each layer and then mixing the results. The individual
layers are usually called octaves.
The number of layers is controlled with a "Detail" slider.
The "Lacunarity" input controls a factor by which each successive layer gets scaled.
The existing Noise node already supports fractal noise. Now the Voronoi Noise node
supports it as well. The node also has a new "Normalize" property that ensures that
the output values stay in a [0.0, 1.0] range. That is except for the F2 feature where
in rare cases the output may be outside that range even with "Normalize" turned on.
How the individual octaves are mixed depends on the feature and output socket:
- F1/Smooth F1/F2:
- Distance/Color output:
The individual Distance/Color octaves are first multiplied by a factor of
`Roughness ^ (#layers - 1.0)` then added together to create the final output.
- Position output:
Each Position octave gets linearly interpolated with the combined output of the
previous octaves. The Roughness input serves as an interpolation factor with
0.0 resutling in only using the combined output of the previous octaves and
1.0 resulting in only using the current highest octave.
- Distance to Edge:
- Distance output:
The Distance octaves are mixed exactly like the Position octaves for F1/Smooth F1/F2.
It should be noted that Voronoi Noise is a relatively slow noise function, especially
at higher dimensions. Increasing the "Detail" makes it even slower. Therefore, when
optimizing a scene one should consider trying to use simpler noise functions instead
of Voronoi if the final result is close enough.
Pull Request: https://projects.blender.org/blender/blender/pulls/106827
So far, each closure in Cycles was either diffuse OR glossy OR
transmissive, and its color and contributions were assigned
to the corresponding direct/indirect/color passes.
However, since Glass is a single closure now, that is no longer enough,
since glass has both a glossy and a transmissive component.
Therefore, this commit adds support for splitting contributions from
the Glass closure between the two types.
For 4.0, we might want to also use this for Principled Hair since it
also technically has both types, but that would be a change from
the existing result so it's not part of 3.6 yet.
The input socket of Image Texture node is connected with the UV output
of Texture Coordinate node by default, the later reads the geometry UV,
which is not available for lights because they have no real geometry.
The current implementation simply retrieves UV from shader data.
Pull Request: https://projects.blender.org/blender/blender/pulls/108691
This is added so that some texture pipeline with point light and spot
light could work as before. Some people use the Normal socket from
Texture Coordinate node for texturing light, however the Normal there is
actually the incoming light direction and should be corrected. Using the
Parametric socket from Geometry node + normal transform from world to
object with Vector Transform node delivers the same result as using the
Normal socket from Texture Coordinate node.
Currently for lights only normal transformation works, because only
there we fetch light transform properly. This is a confusing behaviour,
but testing if it's a lamp in all relevant functions could have bad
impact on the performance. A more proper solution would be to change
lights to real objects, which is planned for the future.
Pull Request: https://projects.blender.org/blender/blender/pulls/108666
While the multiscattering GGX code is cool and solves the darkening problem at higher roughnesses, it's also currently buggy, hard to maintain and often impractical to use due to the higher noise and render time.
In practice, though, having the exact correct directional distribution is not that important as long as the overall albedo is correct and we a) don't get the darkening effect and b) do get the saturation effect at higher roughnesses.
This can simply be achieved by adding a second lobe (https://blog.selfshadow.com/publications/s2017-shading-course/imageworks/s2017_pbs_imageworks_slides_v2.pdf) or scaling the single-scattering GGX lobe (https://blog.selfshadow.com/publications/turquin/ms_comp_final.pdf). Both approaches require the same precomputation and produce outputs of comparable quality, so I went for the simple albedo scaling since it's easier to implement and more efficient.
Overall, the results are pretty good: All scenarios that I tested (Glossy BSDF, Glass BSDF, Principled BSDF with metallic or transmissive = 1) pass the white furnace test (a material with pure-white color in front of a pure-white background should be indistinguishable from the background if it preserves energy), and the overall albedo for non-white materials matches that produced by the real multi-scattering code (with the expected saturation increase as the roughness increases).
In order to produce the precomputed tables, the PR also includes a utility that computes them. This is not built by default, since there's no reason for a user to run it (it only makes sense for documentation/reproducibility purposes and when making changes to the microfacet models).
Pull Request: https://projects.blender.org/blender/blender/pulls/107958
Used to be https://archive.blender.org/developer/D17123.
Internally these are already using the same code path anyways, there's no point in maintaining two distinct nodes.
The obvious approach would be to add Anisotropy controls to the Glossy BSDF node and remove the Anisotropic BSDF node. However, that would break forward compability, since older Blender versions don't know how to handle the Anisotropy input on the Glossy BSDF node.
Therefore, this commit technically removes the Glossy BSDF node, uses versioning to replace them with an Anisotropic BSDF node, and renames that node to "Glossy BSDF".
That way, when you open a new file in an older version, all the nodes show up as Anisotropic BSDF nodes and render correctly.
This is a bit ugly internally since we need to preserve the old `idname` which now no longer matches the UI name, but that's not too bad.
Also removes the "Sharp" distribution option and replaces it with GGX, sets Roughness to zero and disconnects any input to the Roughness socket.
Pull Request: https://projects.blender.org/blender/blender/pulls/104445
In some cases comments at the end of control statements were wrapped
onto new lines which made it read as if they applied to the next line
instead of the (now) previous line.
Relocate comments to the previous line or in some cases the end of the
line (before the brace) to avoid confusion.
Note that in quite a few cases these blocks didn't read well
even before MultiLine was used as comments after the brace caused
wrapping across multiple lines in a way that didn't follow
formatting used everywhere else.
There were two issues here preventing the proper display of the IES
files in question.
The primary one was that these lights are actually vertical. Their
profiles actually point upwards from 90deg to 180deg but our parser was
trying hard to adjust it to start at 0deg incorrectly.
Lastly, the files in question ended with the parser in the `eof`
state - they are "missing" the final carriage return that other IES
files tend to have but other viewers don't seem to mind. Change the
`eof` check instead for a better one that will indicate if any parsing
errors occurred along the way.
Pull Request: https://projects.blender.org/blender/blender/pulls/107320
Due to floating point differences between importance sampling and
texture evaluation, disagreeing on whether or not a ray lies within
the sun disc.
* Use the same input values for geographical_to_direction() in
sky_radiance_nishita() and kernel_data.background.sun.
* The mathematical operations in pdf_uniform_cone() were adjusted to
match sky_radiance_nishita().
Pull Request: https://projects.blender.org/blender/blender/pulls/106764
The name #ensure_valid_reflection seems to indicate that the resulted
reflection must be valid, whereas in the reality it only ensure validity
for specular reflections. The new name matches the behavior better.
This function checks if the shading normal would result in an invalid reflection into the lower hemisphere; if it is the case, the function raises the shading normal just enough so that the specular reflection lies above the surface. This is a trick to prevent dark regions at grazing angles caused by normal/bump maps. However, the specular direction is not a good representation for a diffuse material, applying this function sometimes brightens the result too much and causes unexpected results. This patch applies the function to only glossy materials instead.
Pull Request: #105776
Currently, we use the closure type to encode the type of microfacet distribution
(GGX/Beckmann/Sharp/MultiGGX), the lobes we're interested in
(Reflection/Refraction/both) AND the Fresnel type (None or Principled v1).
This results in the mess of dozens of options that we currently have. Since
adding Principled v2 and the MaterialX OSL closures will involve adding more
Fresnel types, this clearly doesn't scale.
But, since the earlier Fresnel rework (D17101), the Fresnel type only matters
in one place now. This allows to significantly clean up the closure type
handling. To do this, MicrofacetBsdfs now separately store their Fresnel type,
and instead of a single MicrofacetExtra we have one struct per Fresnel type
(unless no extra data is needed).
Further, instead of having one _setup() function per combination, the Fresnel
setup is also split into separate functions. This decouples the implementation
of new Fresnel terms from most of the Microfacet logic, and makes it a very
simple and clean operation.
This commit replaces the current Glass approach, where Glass is a virtual closure
that gets replaced with a Glossy and a Refractive closure, with a combined
closure that handles Fresnel after sampling the microfacet. That way, the Fresnel
term is more accurate since it accounts for the microfacet normal, not the
shading normal.
Also updates the BSDF sampling to use a 3D sampler now, since we need two
dimensions to pick the microfacet normal and then a third dimension to pick
reflection/refraction. This can also be used to get rid of the LCG in the
Principled Hair BSDF, which means we can remove it altogether once MultiGGX is
gone.
Also, "sharp" is now supported as a microfacet distribution in OSL, and 2
is supported as the "refract" argument to microfacet() in order to get glass.
- Rename roughness variables for more clarity - before, the SVM/OSL code would
set s and v to the linear roughness values, and the setup function would over-
write them with the distribution parameters. This actually caused a bug in the
albedo code, since it intended to use the linear roughness value, but ended up
getting the remapped value.
- Deduplicate the evaluation and sample functions. Most of their code is the
same, only the middle part is different.
- Changed albedo computation to return the sum of the intensities of the four
BSDF lobes. Previously, the code applied the inverse of the color->sigma
mapping from the paper - this returns the color specified in the node, but
for very dark hair (e.g. when using the Melanin controls) the result is
extremely low (e.g. 0.000001) despite the hair still reflecting a significant
amount of light (since the R lobe is independent of sigma). This causes issues
with the light component passes, so this change fixes#104586.
- There's quite a few computations at the start of the evaluation function that
are needed for sampling, evaluation and albedo computation, but only depend on
the view direction. Therefore, just precompute them - we still have space in
PrincipledHairExtra after all.
- Fix a tiny bug - the direction sampling code did not account for the R lobe
roughness modifier.
Pull Request #104669
