When Emission Sampling in None, we loop through
kernel_data.integrator.num_lights to find the light intersection.
If the light shader changes, the number of lights might change, so we
need to tag the light manager for update to recount the lights.
Pull Request: https://projects.blender.org/blender/blender/pulls/137605
Area light with a size of zero should not contribute to the scene, so
set the light as disabled.
This does not only fix the reported bug where such light is visible to
the camera, but also a regression in 4.2 where the light contributes to
the scene when light tree is off.
Pull Request: https://projects.blender.org/blender/blender/pulls/136763
This is an intermediate steps towards making lights actual geometry.
Light is now a subclass of Geometry, which simplifies some code.
The geometry is not added to the BVH yet, which would be the next
step and improve light intersection performance with many lights.
This makes object attributes work on lights.
Co-authored-by: Lukas Stockner <lukas@lukasstockner.de>
Pull Request: https://projects.blender.org/blender/blender/pulls/134846
Check was misc-const-correctness, combined with readability-isolate-declaration
as suggested by the docs.
Temporarily clang-format "QualifierAlignment: Left" was used to get consistency
with the prevailing order of keywords.
Pull Request: https://projects.blender.org/blender/blender/pulls/132361
* Use .empty() and .data()
* Use nullptr instead of 0
* No else after return
* Simple class member initialization
* Add override for virtual methods
* Include C++ instead of C headers
* Remove some unused includes
* Use default constructors
* Always use braces
* Consistent names in definition and declaration
* Change typedef to using
Pull Request: https://projects.blender.org/blender/blender/pulls/132361
This is because with the addition of new features to Cycles, these GPUs
experienced significant performance regressions and bugs, all stemming
from bugs in the Metal GPU driver/compiler. The only reasonable way to
work around these issues was to disable parts of Cycles code on
these GPUs to avoid the driver/compiler bugs.
This resulted in increased development time maintaining these platforms
while being unable to deliver feature parity with other
GPU backends.
It has been decided that this development time is better spent
maintaining platforms that are still actively maintained by
hardware/software vendors, and so AMD and Intel GPU support will be
removed from the Metal backend for Cycles.
Pull Request: https://projects.blender.org/blender/blender/pulls/123551
`num_distribution` in `KernelIntegrator` has type `int`, which holds a
maximal value of 2147483647. However, when computing the distribution,
`size_t` is used, which can go beyond this value and result in a
negative value when converted to `int`.
This PR handles this case as an error, stops rendering and suggests
alternative solutions.
Also early return when `use_light_tree`. The block was there because
`num_distribution` was needed for light tree before bfd1836861.
Pull Request: https://projects.blender.org/blender/blender/pulls/123177
by ensuring `KernelLight.lightgroup` is properly assigned in
`device_update_light()`. The value is later retrieved via
`lamp_lightgroup(kg, lamp)`.
`light_manager->device_update()` is called after
`background->device_update()`, so the background light group should
already been assigned when `device_update_lights()` is called.
Pull Request: https://projects.blender.org/blender/blender/pulls/120714
Cycles samples environment map with a PDF proportional to the luminance.
This computation was assuming positive values, but generated texture
coordinates from world could have negative values, so the resulted CDF
was almost zero in the bug report scene.
Fixed by taking the absolute value when computing luminance in CDF.
Pull Request: https://projects.blender.org/blender/blender/pulls/119896
By restricting the sample range along the ray to the valid segment.
Supports
**Mesh Light**
- [x] restrict the ray segment to the side with MIS
**Area Light**
- [x] when the spread is zero, find the intersection of the ray and the bounding box/cylinder of the rectangle/ellipse area light beam
- [x] when the spread is non-zero, find the intersection of the ray and the minimal enclosing cone of the area light beam
*note the result is also unbiased when we just consider the cone from the sampled point in volume segment. Far away from the light source it's less noisy than the current solution, but near the light source it's much noisier. We have to restrict the sample region on the area light to the part that lits the ray then, I haven't tried yet to see if it would be less noisy.*
**Point Light**
- [x] the complete ray segment should be valid.
**Spot Light**
- [x] intersect the ray with the spot light cone
- [x] support non-zero radius
Pull Request: https://projects.blender.org/blender/blender/pulls/119438
For spherical spot light, when the shading point is close to the light
source, we switch to sampling the light spread instead of the visible
cone from the shading point. This has the benefit of less noise when the
spread is small.
However, the light spread sampling was not considering non-uniform
object scaling, where the actual spread might be different.
This patch switches sampling method only when the smallest enclosing
spread cone is smaller than the visible cone from the shading point.
An alternative method would be to compute the actual solid angle of the
scaled cone, and sample from the scaled cone. However, that involves
ray transformation and modifying the sampling pdf and angle. Since
non-uniform scaling is rather a niche case, it's probably not worth the
computation effort.
Pull Request: https://projects.blender.org/blender/blender/pulls/119661
area light with zero spread was introduced in bf18032977. Such paths can
only be sampled with NEE, so MIS should not be used.
This fixes the discrepancy when Direct Light Sampling is set to MIS or NEE.
Pull Request: https://projects.blender.org/blender/blender/pulls/118584
Add new "Soft Falloff" option on point and spot light that uses
the old light behavior from Blender versions before 4.0. Blend
files saved with those older versions will use the option.
This option is enabled by default on new lights.
Fix#114241
Co-authored-by: Weizhen Huang <weizhen@blender.org>
Co-authored-by: Clément Foucault <foucault.clem@gmail.com>
Pull Request: https://projects.blender.org/blender/blender/pulls/117832
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
This is a continuation of a fix from the last week in #108311.
The issue was not fully fixed due to a mistake in the regression
test file.
There are two major things which left to be fixed since the
previous patch:
1. Root nodes can not be shared, even if the local and distant
lights belong to the same light set. If the root node is shared
then the flattening will use the same node index for specialized
trees, which is not a desired behavior.
2. The node type needs to be preserved when a new node is
created for a subset of emitters. This is because tree sampling
in kernel will handle distant and local lights differently for
nodes where there are multiple emitters.
Pull Request: https://projects.blender.org/blender/blender/pulls/108427
This will make further changes for light linking easier, where we want to
build multiple trees specialized for each light linking set.
It's also easier to understand than the stack used previously.
Pull Request: https://projects.blender.org/blender/blender/pulls/107560
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
Make it a native Cycles light option instead of counter-acting the inverse
area calculation in Hydra.
Differential Revision: https://developer.blender.org/D16838
