* 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
This is the minimal change required to start using modern CMake in the
blender build system. This change is designed to allow small
incremental changes to the build system rather than doing it in one
big bang which would be unmaintainable (for me)
The biggest functional change is, previously all libraries in the
`LIB` section of a `blender_add_lib` call had the `INTERFACE` scope,
which is rarely, if ever the correct scope. This diff changes this to
`PRIVATE`
Concrete implications of this diff :
The `LIB`, `INC` and `INC_SYS` sections of an `blender_add_lib` call
now allow scoping keywords (`PUBLIC`, `PRIVATE,` `INTERFACE`) to
declare the scope of the dependency.
Right now the only library using any modern cmake is
`bf_intern_atomic` which is an header only interface library that will
just advertise its include directories.
This allows us to clean up any `CMakeLists.txt` that adds
`../../../intern/atomic` to its `INC` section to remove it in `INC` by
adding a `PRIVATE bf_intern_atomic` to the `LIB` section.
Pull Request: https://projects.blender.org/blender/blender/pulls/107858
- "Front"/"Back": 'put something at the front/back' or 'the front/back
face of something'. (e. g. the Empty Image options, Depth and Side
option, both use the same strings as enum, which should be avoided
in some languages).
- "Flip": invert, as in normals, or mirror, as in an image.
- "Path": a path to a resource, in general a file but sometimes a
datablock, as opposed to a trajectory in space.
- "Join": disambiguate for the Grease Pencil operator, which may use a
different word as that for meshes.
- "Wave": an ondulating motion, as opposed to a fluid dynamics motion.
- "Step": can mean the distance between two things, or a number of
times to do something. In this case it is better to use the plural.
- "Edge": generally the edges of a mesh, but can also mean edge
detection. Additionally, it was used for the option to enable
Freestyle. This was changed to "Use Freestyle".
- "Boundary": the limit of a grease pencil drawing for filling
purposes, as opposed to the external limit of a (non-manifold) mesh.
- "Rotations": can be translated to something like "Turns", in the
context of a spiral.
Pull Request: https://projects.blender.org/blender/blender/pulls/108213
For repeat / extend / mirror mode, both wrap and read_clip functions did
the bounds check. Removing it improves performance between 0.5% and 1.5%
in the classroom scene in one test. Clip mode is unchanged.
Pull Request: https://projects.blender.org/blender/blender/pulls/109304
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
During recent testing, the oldest 101.4032 (windows) and <25812 (linux)
drivers led to crashes during JIT compilation, so we bump the
requirement to newer 101.4313 and 25812.14 drivers that do incorporate
the required fixes.
Pull Request: https://projects.blender.org/blender/blender/pulls/109281
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
When baking only indirect lighting, light sampling is skipped at the
first bounce. However, light evaluation is still done, so depending
on how the MIS weights end up more or less of the direct lighting
still ends up in the bake.
This is most noticeable with background lighting, but can also be
reproduced with e.g. point lights with a large radius.
Pull Request: https://projects.blender.org/blender/blender/pulls/108955
Better to disable than crashing, as we are not expecting a quick fix. The cause
is likely similar to issues with the light tree, which was already disabled.
Ref #104013
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.
Happens with systems which do not provide GOLD linker: the linking state
would failing with some missing symbols and print about missing libsycl.so.6.
Seems that BFD linker expects to resolve all symbols, even the indirectly
used ones. This is somewhat counter-intuitive and is not how LLD, GOLD,
or MOLD worls.
The current state of the CMakeLists.txt does request the cycles_bvh to be
linked against SYCL_LIBRARIES. However, the SYCL was only requested to be found
if WITH_CYCLES_DEVICE_ONEAP is true.
Arguably the SYCL_LIBRARIES should only be linked-in into cycles_bvh if
EMBREE_STATIC_LIB, but that does not solve the issue with BFD.
This change makes it so the SYCL is requested to be found if the oneAPI
device is enabled, or if the Embree is detected to require/use SYCL
support.
Pull Request: https://projects.blender.org/blender/blender/pulls/108965
When baking e.g. the Diffuse pass, use the existing filter logic to
disable glossy and transmission closures.
This reduces baking time and noise when baking individual components
of complex materials.
