**Problem**:
Area lights in Cycles have spread angle, in which case some part of the area light might be invisible to a shading point. The current implementation samples the whole area light, resulting some samples invisible and thus simply discarded. A technique is applied on rectangular light to sample a subset of the area light that is potentially visible (rB3f24cfb9582e1c826406301d37808df7ca6aa64c), however, ellipse (including disk) area lights remained untreated. The purpose of this patch is to apply a techniques to ellipse area light.
**Related Task**:
T87053
**Results**:
These are renderings before and after the patch:
|16spp|Disk light|Ellipse light|Square light (for reference, no changes)
|Before|{F13996789}|{F13996788}|{F13996822}
|After|{F13996759}|{F13996787}|{F13996852}
**Explanation**:
The visible region on an area light is found by drawing a cone from the shading point to the plane where the area light lies, with the aperture of the cone being the light spread.
{F13990078,height=200}
Ideally, we would like to draw samples only from the intersection of the area light and the projection of the cone onto the plane (forming a circle). However, the shape of the intersection is often irregular and thus hard to sample from directly.
{F13990104,height=200}
Instead, the current implementation draws samples from the bounding rectangle of the intersection. In this case, we still end up with some invalid samples outside of the circle, but already much less than sampling the original area light, and the bounding rectangle is easy to sample from.
{F13990125}
The above technique is only applied to rectangle area lights, ellipse area light still suffers from poor sampling. We could apply a similar technique to ellipse area lights, that is, find the
smallest regular shape (rectangle, circle, or ellipse) that covers the intersection (or maybe not the smallest but easy to compute).
For disk area light, we consider the relative position of both circles. Denoting `dist` as the distance between the centre of two circles, and `r1`, `r2` their radii. If `dist > r1 + r2`, the area light is completely invisible, we directly return `false`. If `dist < abs(r1 - r2)`, the smaller circle lies inside the larger one, and we sample whichever circle is smaller. Otherwise, the two circles intersect, we compute the bounding rectangle of the intersection, in which case `axis_u`, `len_u`, `axis_v`, `len_v` needs to be computed anew. Depending on the distance between the two circles, `len_v` is either the diameter of the smaller circle or the length of the common chord.
|{F13990211,height=195}|{F13990225,height=195}|{F13990274,height=195}|{F13990210,height=195}
|`dist > r1 + r2`|`dist < abs(r1 - r2)`|`dist^2 < abs(r1^2 - r2^2)`|`dist^2 > abs(r1^2 - r2^2)`
For ellipse area light, it's hard to find the smallest bounding shape of the intersection, therefore, we compute the bounding rectangle of the ellipse itself, then treat it as a rectangle light.
|{F13990386,height=195}|{F13990385,height=195}|{F13990387,height=195}
We also check the areas of the bounding rectangle of the intersection, the ellipse (disk) light, and the spread circle, then draw samples from the smallest shape of the three. For ellipse light, this also detects where one shape lies inside the other. I am not sure if we should add this measure to rectangle area light and sample from the spread circle when it has smaller area, as we seem to have a better sampling technique for rectangular (uniformly sample the solid angle). Maybe we could add [area-preserving parameterization for spherical
ellipse](https://arxiv.org/pdf/1805.09048.pdf) in the future.
**Limitation**:
At some point we switch from sampling the ellipse to sampling the rectangle, depending on the area of the both, and there seems to be a visible line (with |slope| =1) on the final rendering
which demonstrate at which point we switch between the two methods. We could see that the new sampling method clearly has lower variance near the boundaries, but close to that visible line,
the rectangle sampling method seems to have larger variance. I could not spot any bug in the implementation, and I am not sure if this happens because different sampling patterns for ellipse and rectangle are used.
|Before (256spp)|After (256spp)
|{F13996995}|{F13996998}
Differential Revision: https://developer.blender.org/D16694
Ensure the environment is set up for blender_test, idiff and oslc so that they
can find the required shared libraries.
Also deduplicate add_bundled_libraries() between Linux and macOS.
Includes contributions by Ray Molenkamp and Brecht Van Lommel.
Ref T99618
Uses a light tree to more effectively sample scenes with many lights. This can
significantly reduce noise, at the cost of a somewhat longer render time per
sample.
Light tree sampling is enabled by default. It can be disabled in the Sampling >
Lights panel. Scenes using light clamping or ray visibility tricks may render
different as these are biased techniques that depend on the sampling strategy.
The implementation is currently disabled on AMD HIP. This is planned to be fixed
before the release.
Implementation by Jeffrey Liu, Weizhen Huang, Alaska and Brecht Van Lommel.
Ref T77889
This was not working well in non-trivial scenes before the light tree, and now
it is even harder to make it work well with the light tree. It would average the
with equal weight for every light object regardless of intensity or distance, and
be quite noisy due to not working with multiple importance sampling.
We may restore this if were enough good use cases for the previous implementation,
but let's wait and see what the feedback is.
Some uses cases for this have been replaced by the shadow catcher passes, which
did not exist when this was added.
Ref T77889
In this case the blocksize may not the one we requested, which was assumed to be
the case. Instead get the effective block size from the compiler as was already
done for Metal and OneAPI.
Unless using WITH_CYCLES_DEBUG.
This is convenient for investigating kernel performance, but too verbose to
always have in the buildbot logs especially now that we are also compiling HIP
and OneAPI kernels.
Materials now have an enum to set the emission sampling method, to be
either None, Auto, Front, Back or Front & Back. This replace the
previous "Multiple Importance Sample" option.
Auto is the new default, and uses a heuristic to estimate the emitted
light intensity to determine of the mesh should be considered as a light
for sampling. Shaders sometimes have a bit of emission but treating them
as a light source is not worth the memory/performance overhead.
The Front/Back settings are not important yet, but will help when a
light tree is added. In that case setting emission to Front only on
closed meshes can help ignore emission from inside the mesh interior that
does not contribute anything.
Includes contributions by Brecht Van Lommel and Alaska.
Ref T77889
* Split light types into own files, move light type specific code from
light tree and MNEE.
* Move flat light distribution code into own kernel file and host side
building function, in preparation of light tree addition. Add light/sample.h
as main entry point to kernel light sampling.
* Better separate calculation of pdf for selecting a light, and pdf for
sampling a point on the light. The selection pdf is now also stored in
LightSampling for MNEE to correctly recalculate the full pdf when the
shading position changes but the point on the light remains fixed.
* Improvement to kernel light storage, using packed_float3, better variable
names, etc.
Includes contributions by Brecht Van Lommel and Weizhen Huang.
Ref T77889
The wrong guiding distribution was used when direct and indirect light
scattering happened at different locations. Now use a different distribution
for each location.
Recording is not quite correct since OpenPGL does not support spliting the
path like this, instead recording at the start of the volume ray. In practice
this seems to make little difference.
Differential Revision: https://developer.blender.org/D16448
This resolves some issues with correlation artifacts at higher sample counts.
Fix T101356, correlation issues in new PMJ pattern.
Differential Revision: https://developer.blender.org/D16561
Commit c8dd33f5a37b6a6db0b6950d24f9a7cff5ceb799 in OSL changed behavior of
parameters that reference each other and are also overwritten with an
instance value. This is causing the "NormalIn" parameter of a few OSL nodes
in Cycles to be set to zero somehow, which should instead have received the
value from a "node_geometry" node Cycles generates and connects automatically.
I am not entirely sure why that is happening, but these parameters are
superfluous anyway, since OSL already provides the necessary data in the
global variable "N". So this patch simply removes those parameters (which
mimics SVM, where these parameters do not exist either), which also fixes
the rendering artifacts that occured with recent OSL.
While this fixes built-in shader nodes, custom OSL scripts can still have
this problem.
Ref T101222
Differential Revision: https://developer.blender.org/D16470
For some pixels with transparent surfaces, no depth value would be written
when sampling chooses a reflection/refraction BSDF instead of transparent
BSDF. Now ensure we always write at some some depth value to the pass.
This is still not ideal as the resulting depth values are noisy same as they
are for depth of field and motion blur, but at least there should be no gaps.
This was previously needed due to poor compatibility between Visual Studio and
NVCC. But it has not been used for a while now as compatibility seems to have
improved.
Render time is reduced for overexposed scenes, by taking into account absolute
light intensity for adaptive sampling.
This can negatively affect some scenes where compositing or color management
are used to make the scene much darker or lighter. For best results adjust the
Film > Exposure setting to bring the intensity into a good range, and then do
further compositing and color management on top of that. Note that this setting
is different than color management exposure.
Previously Cycles' adaptive sampling used sqrt(I) to normalize noise level to
conform to a viewer's eye sensitivity. It is great for darker regions of the
image, but also requests too much samples in bright regions, sometimes several
times more than needed. Highlights can tolerate more noise because in most
examples it is still less noticeable then the noise in darker areas in the same
render.
Differential Revision: https://developer.blender.org/D16392
The OSL GPU services implementation of "osl_get_matrix" and
"osl_get_inverse_matrix" was missing support for the "common",
"shader" and "object" matrices and thus any matrix operations in OSL
shaders using these would not work. This patch adds the proper
implementation copied from the OSL CPU services.
Maniphest Tasks: T101222
Commit c8dd33f5a37b6a6db0b6950d24f9a7cff5ceb799 in OSL
changed behavior of shader parameters that reference each other
and are also overwritten with an instance value.
This is causing the "NormalIn" parameter of a few OSL nodes in
Cycles to be set to zero somehow, which should instead have
received the value from a "node_geometry" node Cycles generates
and connects automatically. I am not entirely sure why that is
happening, but these parameters are superfluous anyway, since
OSL already provides the necessary data in the global variable "N".
So this patch simply removes those parameters (which mimics
SVM, where these parameters do not exist either), which also
fixes the rendering artifacts that occured with recent OSL.
Maniphest Tasks: T101222
Differential Revision: https://developer.blender.org/D16470
This patch generalizes the OSL support in Cycles to include GPU
device types and adds an implementation for that in the OptiX
device. There are some caveats still, including simplified texturing
due to lack of OIIO on the GPU and a few missing OSL intrinsics.
Note that this is incomplete and missing an update to the OSL
library before being enabled! The implementation is already
committed now to simplify further development.
Maniphest Tasks: T101222
Differential Revision: https://developer.blender.org/D15902
The distinction existed for legacy reasons, to easily port of Embree
intersection code without affecting the main vector types. However we are now
using SIMD for these types as well, so no good reason to keep the distinction.
Also more consistently pass these vector types by value in inline functions.
Previously it was partially changed for functions used by Metal to avoid having
to add address space qualifiers, simple to do it everywhere.
Also removes function declarations for vector math headers, serves no real
purpose.
Differential Revision: https://developer.blender.org/D16146
This can be used for example for VR video formats that use this projection
instead of perspective projection for cubemap faces.
Differential Revision: https://developer.blender.org/D13525
Buildbot infrastructure relies on the fact that it can enable and
disable `WITH_CYCLES_<COMPUTE>_BINARIES` without affecting speed of
incremental builds. This allows buildbot to skip GPU kernels when
doing CI regression tests which do not need GPU kernels, as well as
it allows to move GPU kernels compilation to a separate step where
all the resources are available to the GPU kernel builders.
For the oneAPI compute enabling and disabling AoT kernels has much
higher implications due to the kernels being a part of the device
implementation from the build target perspective.
This change makes it so different target names are used for JIT and
AoT configurations, which allows CMake to more fully benefit from
"caching" the compiled result.
The end goal of this change is to make it so sequential build of the
same code base on the buildbot happens super fast,
Blender binary still needs to be re-linked when the AOT of oneAPI
option is toggled, but that's already the case in the buildbot due
to the WITH_BUILDINFO.
Differential Revision: https://developer.blender.org/D16312
Known Issues:
- Command buffer failures when using binary archives (binary archives is disabled for Intel GPUs as a workaround)
- Wrong texture sampler being applied (to be addressed in the future)
Ref T92212
Reviewed By: brecht
Maniphest Tasks: T92212
Differential Revision: https://developer.blender.org/D16253
Previously, a first build using ninja would throw "ninja: error:
'intern/cycles/kernel/cycles_kernel_oneapi.lib', needed by
'bin/blender.exe', missing and no known rule to make it".
