- Add missing doxy-section for Apply Parent Inverse Operator
- Use identity for None comparison in Python.
- Remove newline from operator doc-strings.
- Use '*' prefix multi-line C comment blocks.
- Separate filenames from doc-strings.
- Remove break after return.
Remove need for shadow caustic caster geometry to have a UV layout. UVs were
useful to maintain a consistent tangent frame across the surface while
performing the walk. A consistent tangent frame is necessary for rough
surfaces where a normal offset encodes the sampled h, which should point
towards the same direction across the mesh.
In order to get a continuous surface parametrization without UVs, the
technique described in this paper was implemented:
"The Natural-Constraint Representation of the Path Space for Efficient
Light Transport Simulation" (Supplementary Material), SIGGRAPH 2014.
In addition to implementing this feature:
* Shadow caustic casters without smooth normals are now ignored (triggered
some refactoring and cleaning).
* Hit point calculation was refactored using existing utils functions,
simplifying the code.
* The max number of solver iterations was reduced to 32, a solution is
usually found by then.
* Added generalized geometry term clamping (transfer matrix calculation can
sometimes get unstable).
* Add stop condition to Newton solver for more consistent CPU and GPU result.
* Add support for multi scatter GGX refraction.
Fixes T96990, T96991
Ref T94120
Differential Revision: https://developer.blender.org/D14623
This adds support for rendering motion blur for volumes, using their
velocity field. This works for fluid simulations and imported VDB
volumes. For the latter, the name of the velocity field can be set per
volume object, with automatic detection of velocity fields that are
split into 3 scalar grids.
A new parameter is also added to scale velocity for more artistic control.
Like for Alembic and USD caches, a parameter to set the unit of time in
which the velocity vectors are expressed is also added. For Blender gas
simulations, the velocity unit should always be in seconds, so this is
only exposed for volume objects which may come from external OpenVDB
files.
These parameters are available under the `Render` panels for the fluid
domain and the volume object data properties respectively.
Credits: kernel advection code from Tangent Animation's Blackbird based
on earlier work by Geraldine Chua
Differential Revision: https://developer.blender.org/D14629
Stumbled over the `integrate_surface_volume_only_bounce` kernel
function not returning the right type. The others too showed up as
warnings when building Cycles as a standalone which didn't have
those warnings disabled.
Differential Revision: https://developer.blender.org/D14558
Light groups are a type of pass that only contains lighting from a subset of light sources.
They are created in the View layer, and light sources (lamps, objects with emissive materials
and/or the environment) can be assigned to a group.
Currently, each light group ends up generating its own version of the Combined pass.
In the future, additional types of passes (e.g. shadowcatcher) might be getting their own
per-lightgroup versions.
The lightgroup creation and assignment is not Cycles-specific, so Eevee or external render
engines could make use of it in the future.
Note that Lightgroups are identified by their name - therefore, the name of the Lightgroup
in the View Layer and the name that's set in an object's settings must match for it to be
included.
Currently, changing a Lightgroup's name does not update objects - this is planned for the
future, along with other features such as denoising for light groups and viewing them in
preview renders.
Original patch by Alex Fuller (@mistaed), with some polishing by Lukas Stockner (@lukasstockner97).
Differential Revision: https://developer.blender.org/D12871
This adds support for selective rendering of caustics in shadows of refractive
objects. Example uses are rendering of underwater caustics and eye caustics.
This is based on "Manifold Next Event Estimation", a method developed for
production rendering. The idea is to selectively enable shadow caustics on a
few objects in the scene where they have a big visual impact, without impacting
render performance for the rest of the scene.
The Shadow Caustic option must be manually enabled on light, caustic receiver
and caster objects. For such light paths, the Filter Glossy option will be
ignored and replaced by sharp caustics.
Currently this method has a various limitations:
* Only caustics in shadows of refractive objects work, which means no caustics
from reflection or caustics that outside shadows. Only up to 4 refractive
caustic bounces are supported.
* Caustic caster objects should have smooth normals.
* Not currently support for Metal GPU rendering.
In the future this method may be extended for more general caustics.
TECHNICAL DETAILS
This code adds manifold next event estimation through refractive surface(s) as a
new sampling technique for direct lighting, i.e. finding the point on the
refractive surface(s) along the path to a light sample, which satisfies Fermat's
principle for a given microfacet normal and the path's end points. This
technique involves walking on the "specular manifold" using a pseudo newton
solver. Such a manifold is defined by the specular constraint matrix from the
manifold exploration framework [2]. For each refractive interface, this
constraint is defined by enforcing that the generalized half-vector projection
onto the interface local tangent plane is null. The newton solver guides the
walk by linearizing the manifold locally before reprojecting the linear solution
onto the refractive surface. See paper [1] for more details about the technique
itself and [3] for the half-vector light transport formulation, from which it is
derived.
[1] Manifold Next Event Estimation
Johannes Hanika, Marc Droske, and Luca Fascione. 2015.
Comput. Graph. Forum 34, 4 (July 2015), 87–97.
https://jo.dreggn.org/home/2015_mnee.pdf
[2] Manifold exploration: a Markov Chain Monte Carlo technique for rendering
scenes with difficult specular transport Wenzel Jakob and Steve Marschner.
2012. ACM Trans. Graph. 31, 4, Article 58 (July 2012), 13 pages.
https://www.cs.cornell.edu/projects/manifolds-sg12/
[3] The Natural-Constraint Representation of the Path Space for Efficient
Light Transport Simulation. Anton S. Kaplanyan, Johannes Hanika, and Carsten
Dachsbacher. 2014. ACM Trans. Graph. 33, 4, Article 102 (July 2014), 13 pages.
https://cg.ivd.kit.edu/english/HSLT.php
The code for this samping technique was inserted at the light sampling stage
(direct lighting). If the walk is successful, it turns off path regularization
using a specialized flag in the path state (PATH_MNEE_SUCCESS). This flag tells
the integrator not to blur the brdf roughness further down the path (in a child
ray created from BSDF sampling). In addition, using a cascading mechanism of
flag values, we cull connections to caustic lights for this and children rays,
which should be resolved through MNEE.
This mechanism also cancels the MIS bsdf counter part at the casutic receiver
depth, in essence leaving MNEE as the only sampling technique from receivers
through refractive casters to caustic lights. This choice might not be optimal
when the light gets large wrt to the receiver, though this is usually not when
you want to use MNEE.
This connection culling strategy removes a fair amount of fireflies, at the cost
of introducing a slight bias. Because of the selective nature of the culling
mechanism, reflective caustics still benefit from the native path
regularization, which further removes fireflies on other surfaces (bouncing
light off casters).
Differential Revision: https://developer.blender.org/D13533
When the light direction is not pointing away from the geometric normal and
there is a shadow terminator offset, self intersection is supposed to occur.
Without ray offsets intersections at neigbhoring triangles are found, as
the ray start is exactly at the vertex. There was a small offset towards
the center of the triangle, but not enough.
Now this offset computation is moved into Cycles and modified for better
results. It's still not perfect though like any offset approach, especially
with long thin triangles.
Additionaly, this uses the shadow terminate offset for AO rays now, which
helps remove some pre-existing artifacts.
* Replace license text in headers with SPDX identifiers.
* Remove specific license info from outdated readme.txt, instead leave details
to the source files.
* Add list of SPDX license identifiers used, and corresponding license texts.
* Update copyright dates while we're at it.
Ref D14069, T95597
Remove small ray offsets that were used to avoid self intersection, and leave
that to the newly added primitive object/prim comparison. These changes together
significantly reduce artifacts on small, large or far away objects.
The balance here is that overlapping primitives are not handled well and should
be avoided (though this was already an issue). The upside is that this is
something a user has control over, whereas the other artifacts had no good
manual solution in many cases.
There is a known issue where the Blender particle system generates overlapping
objects and in turn leads to render differences between CPU and GPU. This will
be addressed separately.
Differential Revision: https://developer.blender.org/D12954
* Spot lights are now handled as disks aligned with the direction of the
spotlight instead of view aligned disks.
* Point light is now handled separately from the spot light, to fix a case
where multiple lights are intersected in a row. Before the origin of the
ray was the previously intersected light and not the origin of the initial
ray traced from the last surface/volume interaction.
This makes both strategies in multiple importance sampling converge to the same
result. It changes the render results in some scenes, for example the junkshop
scene where there are large point lights overlapping scene geometry and each
other.
Differential Revision: https://developer.blender.org/D13233
This patch adds MetalRT support to Cycles kernel code. It is mostly additive in nature or confined to Metal-specific code, however there are a few areas where this interacts with other code:
- MetalRT closely follows the Optix implementation, and in some cases (notably handling of transforms) it makes sense to extend Optix special-casing to MetalRT. For these generalisations we now have `__KERNEL_GPU_RAYTRACING__` instead of `__KERNEL_OPTIX__`.
- MetalRT doesn't support primitive offsetting (as with `primitiveIndexOffset` in Optix), so we define and populate a new kernel texture, `__object_prim_offset`, containing per-object primitive / curve-segment offsets. This is referenced and applied in MetalRT intersection handlers.
- Two new BVH layout enum values have been added: `BVH_LAYOUT_METAL` and `BVH_LAYOUT_MULTI_METAL_EMBREE` for XPU mode). Some host-side enum case handling has been updated where it is trivial to do so.
Ref T92212
Reviewed By: brecht
Maniphest Tasks: T92212
Differential Revision: https://developer.blender.org/D13353
With very long ray distance, OptiX ends up traversing many BVH nodes due to
a feature that improves precision. However this causes very slow rendering.
We now avoid generating such long rays by rejecting the few samples that have
long ray distances and very low probability of being generated. This should not
meaningfully affect render results.
Thanks to Sergey and Patrick for the investigation.
This patch adds a CMake option "WITH_CYCLES_DEBUG" which builds cycles with
a feature that allows debugging/selecting the direct-light sampling strategy.
The same option may later be used to add other debugging features that could
affect performance in release builds.
The three options are:
* Forward path tracing (e.g., via BSDF or phase function)
* Next-event estimation
* Multiple importance sampling combination of the previous two methods
Such a feature is useful for debugging light different sampling, evaluation,
and pdf methods (e.g., for light sources and BSDFs).
Differential Revision: https://developer.blender.org/D13152
Introduce a packed_float3 type for smaller storage that is exactly 3
floats, instead of 4. For computation float3 is still used since it can
use SIMD instructions.
Ref T92212
Differential Revision: https://developer.blender.org/D13243
This patch adapts the existing volumetric read/write lambda functions for Metal. Lambda expressions are not supported on MSL, so two new macros `VOLUME_READ_LAMBDA` and `VOLUME_WRITE_LAMBDA` have been defined with a default implementation which, on Metal, is overridden to use inline function objects.
This patch also removes the last remaining mention of the now-unused `ccl_addr_space`.
Ref T92212
Reviewed By: leesonw
Maniphest Tasks: T92212
Differential Revision: https://developer.blender.org/D13234
We need to increase GPU memory usage a bit. Unfortunately we can't get away
with writing either reflection or transmission passes because these BSDFs may
scatter in either direction but still must be in a fixed reflection or
transmission category to match up with the color passes.
The issue was caused by splitting happening twice.
Fixed by checking for split flag which is assigned to the both states
during split.
The tricky part was to write catcher data at the moment of split: the
transparency and shadow catcher sample count is to be accumulated at
that point. Now it is happening in the `intersect_closest` kernel.
The downside is that render buffer is to be passed to the kernel, but
the benefit is that extra split bounce check is not needed now.
Had to move the passes write to shadow catcher header, since include
of `film/passes.h` causes all the fun of requirement to have BSDF
data structures available.
Differential Revision: https://developer.blender.org/D13177
This patch exposes the sampling offset option to Blender. It is located in the "Sampling > Advanced" panel.
For example, this can be useful to parallelize rendering and distribute different chunks of samples for each computer to render.
---
I also had to add this option to `RenderWork` and `RenderScheduler` classes so that the sample count in the status string can be calculated correctly.
Reviewed By: leesonw
Differential Revision: https://developer.blender.org/D13086
Changes:
* After hitting a shadow catcher, re-initialize the volume stack taking
into account shadow catcher ray visibility. This ensures that volume objects
are included in the stack only if they are shadow catchers.
* If there is a volume to be shaded in front of the shadow catcher, the split
is now performed in the shade_volume kernel after volume shading is done.
* Previously the background pass behind a shadow catcher was done as part of
the regular path, now it is done as part of the shadow catcher path.
For a shadow catcher path with volumes and visible background, operations are
done in this order now:
* intersect_closest
* shade_volume
* shadow catcher split
* intersect_volume_stack
* shade_background
* shade_surface
The world volume is currently assumed to be CG, that is it does not exist in
the footage. We may consider adding an option to control this, or change the
default. With a volume object this control is already possible.
This includes refactoring to centralize the logic for next kernel scheduling
in intersect_closest.h.
Differential Revision: https://developer.blender.org/D13093
We need to store the continuation probability used to make the termination
decision in intersect_closest, instead of recomputing it in shade_surface.
Because otherwise a shade_volume in between can change the throughput and
change the probability.
