One of the properties of Perlin noise is that it always evaluates to 0.0
when not normalized (or 0.5 when normalized) when the input consists of
only whole integers in all vector components.
Blender's Perlin noise implementation uses single precision floats with
a machine epsilon of 1.19e-07 meaning that for numbers that are greater
than 1/(1.19e-07) = 8.40e6 there mantissa doesn't have any bits left to
store a rational part of the number, effectively meaning that any number
greater than 8.40e6 is a whole integer as far as Blender is concerned.
Therefore when evaluating Perlin noise for any coordinates greater than
that it always results in 0.0 (or 0.5 when normalized).
This fix works as follows: If the original input number is larger than
1.0e6 it is offset by 0.5 after it underwent modulo, which always outputs
numbers in a [0.0, 1.0e5) range leaving the mantissa room for a rational
part. This way the quantization error still persists however the outputs
are random again instead of a constant 0.0.
Pull Request: https://projects.blender.org/blender/blender/pulls/122112
This is an implementation of thin film iridescence in the Principled BSDF based on "A Practical Extension to Microfacet Theory for the Modeling of Varying Iridescence".
There are still several open topics that are left for future work:
- Currently, the thin film only affects dielectric Fresnel, not metallic. Properly specifying thin films on metals requires a proper conductive Fresnel term with complex IOR inputs, any attempt of trying to hack it into the F82 model we currently use for the Principled BSDF is fundamentally flawed. In the future, we'll add a node for proper conductive Fresnel, including thin films.
- The F0/F90 control is not very elegantly implemented right now. It fundamentally works, but enabling thin film while using a Specular Tint causes a jump in appearance since the models integrate it differently. Then again, thin film interference is a physical effect, so of course a non-physical tweak doesn't play nicely with it.
- The white point handling is currently quite crude. In short: The code computes XYZ values of the reflectance spectrum, but we'd need the XYZ values of the product of the reflectance spectrum and the neutral illuminant of the working color space. Currently, this is addressed by just dividing by the XYZ values of the illuminant, but it would be better to do a proper chromatic adaptation transform or to use the proper reference curves for the working space instead of the XYZ curves from the paper.
Pull Request: https://projects.blender.org/blender/blender/pulls/118477
Transport rays that enter to another location in the scene, with
specified ray position and normal. This may be used to render portals
for visual effects, and other production rendering tricks.
This acts much like a Transparent BSDF. Render passes are passed
through, and this is affected by light path max transparent bounces.
Pull Request: https://projects.blender.org/blender/blender/pulls/114386
Clamp some of the inputs of the Glossy BSDF, Glass BSDF, Sheen BSDF,
and Subsurface Scattering nodes to improve consistency between render
engines and to avoid unexpected results.
* Clamp roughness to 0..1
* Clamp subsurface radius to 0..inf
* Clamp colors to 0..inf
Pull Request: https://projects.blender.org/blender/blender/pulls/120390
The Perlin noise algorithms suffer from precision issues when a coordinate
is greater than about 250000.
To fix this the Perlin noise texture is repeated every 100000 on each axis.
This causes discontinuities every 100000, however at such scales this
usually shouldn't be noticeable.
Pull Request: https://projects.blender.org/blender/blender/pulls/119884
for a camera ray, compute the actual range of the hair width that the
current pixel covers, and only integrate that subset, to prevent a
ribbon-like appearance in close-up looks.
When the hair covers less than one pixel on the screen or when the ray
is not camera ray, the model works the same as before.
Pull Request: https://projects.blender.org/blender/blender/pulls/116094
These are now included in the OSL shared libraries, so no reason to
link against it.
The CMake code for WITH_LLVM remains in case it is useful in the future,
but is not enabled by any Blender feature now.
Pull Request: https://projects.blender.org/blender/blender/pulls/118229
This allows users to turn off reflective and refractive caustics
separately from each other when using the Generalized Schlick material.
This will impact the Principled BSDF and Glass BSDF, along with some
custom OSL scripts.
Pull Request: https://projects.blender.org/blender/blender/pulls/117617
Improve the handling of Principled BSDF Caustics from Metallic
and Transmissive components, improving consistency between SVM and OSL,
and offering more predictable results.
Pull Request: https://projects.blender.org/blender/blender/pulls/115081
Along with the 4.1 libraries upgrade, we are bumping the clang-format
version from 8-12 to 17. This affects quite a few files.
If not already the case, you may consider pointing your IDE to the
clang-format binary bundled with the Blender precompiled libraries.
Fix issues related to NaN normals in some situations by trying
to detect when these cases might occur and just reverting back
to default normals.
As a side effect of these changes, OSL now behaves correctly
when given a non-normalized normal.
Pull Request: https://projects.blender.org/blender/blender/pulls/114960
This was required for OSL, which used to be compiled entirely without
RTTI for LLVM. However OSL now only compiles a private part of its code
without RTTI, so this no longer necessary.
Pull Request: https://projects.blender.org/blender/blender/pulls/116035
This path merges the Musgrave and Noise Texture nodes into a single
combined Noise Texture node. The reasoning is that both nodes
intrinsically do the same thing, which is the layering of Perlin noise
derivatives to produce fractal noise. So the patch de-duplicates code
and unifies the use of fractal noise for the end use.
Since the Noise node had a Distortion input and a Color output, while
the Musgrave node did not, those are now available to the Musgrave types
as new functionalities.
The Dimension input of the Musgrave node is analogous to the Roughness
input of the Noise node, so both inputs were unified to follow the same
behavior of the Roughness input, which is arguable more intuitive to
control. Similarly, the Detail input was slightly different across both
nodes, since the Noise node evaluated one extra layer of noise. This was
also unified to follow the behavior of the Noise node.
The patch, coincidentally fixes an unreported bug causing repeated
output for certain noise types and another floating precision bug
#112180.
The versioning code implemented with this patch ensures backward
compatibility for both the Musgrave and Noise Texture nodes. When
opening older Blender files in Blender 4.1 the output of both nodes are
guaranteed to always be exactly identical to that of Blender files
created before the nodes were merged in all cases.
Forward compatibility with Blender 4.0 is implemented by #114236.
Forward compatibility with Blender 3.6 LTS is implemented by #115015.
Pull Request: #111187
Adjust clamping of inputs in the Principled BSDF to avoid errors and
inconsistencies between render engines, while trying to leave as many
inputs as possible unclamped for artisitc purposes.
Pull Request: https://projects.blender.org/blender/blender/pulls/112895
The previous formula for adjusting Coat Tint intensity resulted
in strong tints and sudden colour changes when using a low coat weight.
This commit fixes these issues by mixing between a white tint (no tint)
and the chosen tint based on the Coat Weight.
Pull Request: https://projects.blender.org/blender/blender/pulls/113468
Update the OSL script for the "Geometry" node to follow the correct
Tangent code path when working with point clouds.
There should be no functional change for the end user since the correct
code path was already taken by accident.
Pull Request: https://projects.blender.org/blender/blender/pulls/113472
Update the Glass BSDF to internally use Generalized Schlick fresnel.
This allows for easier expansion of certain features in the future.
There should be no functional change from the users perspective.
Pull Request: https://projects.blender.org/blender/blender/pulls/112701
This keeps the behavior similar to the Disney BRDF, where 0.5
is neutral and lower/higher values respectively decrease/increase
the dielectric specular. But it's more correct in that it's not
an arbitrary scale on Fresnel, but rather adjusting the IOR.
Ref #99447
Ref #112848
Pull Request: https://projects.blender.org/blender/blender/pulls/112552
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 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.
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.
