Cycles has supported path-traced subsurface scattering for a while, but while it's
more accurate than other approaches, the increase in noise makes it an expensive option.
To improve this, this patch implements Dwivedi guiding, a technique that is based on
zero-variance random walk theory from particle physics and helps to produce shorter
random walks with more consistent throughput.
The idea behind this is that in non-white materials, each scattering event inside the
medium reduces the path throughput. Therefore, the darker the material is, the lower the
contribution of paths that travel far from the origin is.
In order to reduce variance, Dwivedi guiding uses modified direction and distance sampling
functions that favor paths which go back towards the medium interface.
By carefully selecting these sampling distributions, variance can be greatly reduced, and
as a neat side effect shorter paths are produced, which speeds up the process.
One limitation of just blindly applying this is that the guiding is derived from the
assumption of a medium that covers an infinite half-space. Therefore, at corners or thin
geometry where this does not hold, the algorithm might lead to fireflies.
To avoid this, the implementation here uses MIS to combine the classic and guided sampling.
Since each of those works on one of the three color channels, the final estimator combines
six sampling techniques. This results in some unintuitive math, but I tried to structure
it in a way that makes some sense.
Another improvement is that in areas where the other side of the mesh is close (e.g. ears),
the algorithm has a chance to switch to guiding towards the other side. This chance is based
on how deep the random walk is inside the object, and once again MIS is applied to the
decision, giving a total of nine techniques.
Combining all this, the noise of path-traced subsurface scattering is reduced significantly.
In my testing with the Rain character model and a simple lighting setup, the path-traced
SSS is now actually less noisy than the Christensen-Burley approximation at same render time
while of course still being significantly more realistic.
Differential Revision: https://developer.blender.org/D9932
Removal of Win32 code that allows background windows to receive raw input.
Differential Revision: https://developer.blender.org/D10408
Reviewed by Brecht Van Lommel
Ref T84819
Build System
============
This is an API breaking new version, and the updated code only builds with
OpenColorIO 2.0 and later. Adding backwards compatibility was too complicated.
* Tinyxml was replaced with Expat, adding a new dependency.
* Yaml-cpp is now built as a dependency on Unix, as was already done on Windows.
* Removed currently unused LCMS code.
* Pystring remains built as part of OCIO itself, since it has no good build system.
* Linux and macOS check for the OpenColorIO verison, and disable it if too old.
Ref D10270
Processors and Transforms
=========================
CPU processors now need to be created to do CPU processing. These are cached
internally, but the cache lookup is not fast enough to execute per pixel or
texture sample, so for performance these are now also exposed in the C API.
The C API for transforms will no longer be needed afer all changes, so remove
it to simplify the API and fallback implementation.
Ref D10271
Display Transforms
==================
Needs a bit more manual work constructing the transform. LegacyViewingPipeline
could also have been used, but isn't really any simpler and since it's legacy
we better not rely on it.
We moved more logic into the opencolorio module, to simplify the API. There is
no need to wrap a dozen functions just to be able to do this in C rather than C++.
It's also tightly coupled to the GPU shader logic, and so should be in the same
module.
Ref D10271
GPU Display Shader
==================
To avoid baking exposure and gamma into the GLSL shader and requiring slow
recompiles when tweaking, we manually apply them in the shader. This leads
to some logic duplicaton between the CPU and GPU display processor, but it
seems unavoidable.
Caching was also changed. Previously this was done both on the imbuf and
opencolorio module levels. Now it's all done in the opencolorio module by
simply matching color space names. We no longer use cacheIDs from OpenColorIO
since computing them is expensive, and they are unlikely to match now that
more is baked into the shader code.
Shaders can now use multiple 2D textures, 3D textures and uniforms, rather
than a single 3D texture. So allocating and binding those adds some code.
Color space conversions for blending with overlays is now hardcoded in the
shader. This was using harcoded numbers anyway, if this every becomes a
general OpenColorIO transform it can be changed, but for now there is no
point to add code complexity.
Ref D10273
CIE XYZ
=======
We need standard CIE XYZ values for rendering effects like blackbody emission.
The relation to the scene linear role is based on OpenColorIO configuration.
In OpenColorIO 2.0 configs roles can no longer have the same name as color
spaces, which means our XYZ role and colorspace in the configuration give an
error.
Instead use the new standard aces_interchange role, which relates scene linear
to a known scene referred color space. Compatibility with the old XYZ role is
preserved, if the configuration file has no conflicting names.
Also includes a non-functional change to the configuraton file to use an
XYZ-to-ACES matrix instead of REC709-to-ACES, makes debugging a little easier
since the matrix is the same one we have in the code now and that is also
found easily in the ACES specs.
Ref D10274
Baking vertex colors per-corner leads to unwanted discontinuities when there is
sampling noise, for example in ambient occlusion or with a bevel shader node for
normals. For this reason the code used to always average results per-vertex.
However when using split normals, multiple materials or UV islands, we do want to
preserve discontinuities. So now bake per corner, but make sure the sampling seed
is shared for vertices.
Fix T85550: vertex color baking crash with split normals, Ref D10399
Fix T84663: vertex color baking blending at UV seams
This patch will share the AOV settings between Cycles and Eevee.
It enable using the AOV name conflict detection of Blender. This
means that unlike how Cycles used to work it isn't possible to add an
AOV with a similar name. Conflicts with internal render pass names will
be indicated with an Warning icon.
Reviewed By: Brecht van Lommel
Differential Revision: https://developer.blender.org/D9774
This crash is caused by accessing object data in the kernel at an out of bound index from a deleted instance.
Cycles represents instances as Object nodes sharing the same Geometry node, so we need to tag the GeometryManager for an update if some objects are added or removed as no geometry might have been added or removed in order to properly update the BVH and its associated data arrays.
Regression caused by rBbbe6d4492823.
* USD and OpenVDB headers use deprecated TBB headers, suppress all deprecation
warnings there since we have no control over them.
* For our own TBB includes, use the individual headers rather than the tbb.h that
includes everything to avoid warnings, rather than suppressing all.
This is in anticipation of the TBB 2020 upgrade in D10359. Ref D10361.
Simplification of window creation code to allow greater flexibility.
Differential Revision: https://developer.blender.org/D10311
Reviewed by Brecht Van Lommel
Simplification of Win32 GHOST_WindowWin32 with improved support for owned windows.
Differential Revision: https://developer.blender.org/D9971
Reviewed by Brecht Van Lommel
Eevee is now used for Freestyle rendering by default, since other engines are
unlikely to have support for this. Workbench and Cycles do their own rendering.
RenderEngine add-ons can do their own Freestyle rendering by setting
bl_use_custom_freestyle = True.
Differential Revision: https://developer.blender.org/D8335
Commit 6e74a8b69f changed the denoiser input passes default to
include the normal pass. This does not always produce optimal images though, hence why the
default was previously set to only include the color and albedo passes. This restores that behavior, so
that viewport denoising with OptiX produces the same results as before.
The "cuda_mem_map_mutex" was potentially being locked recursively during the call to
"CUDADevice::move_textures_to_host", which crashed. This moves around the locking and
unlocking of "cuda_mem_map_mutex", so that it doesn't call a function that locks it while
still holding the lock.
Reviewed By: pmoursnv
Maniphest Tasks: T85089, T84734
Differential Revision: https://developer.blender.org/D10219
The changes to the socket API were not applied to the standalone app.
Also modify Camera.compute_auto_viewplane() to use Camera.full_width and Camera.full_height as it is not possible to publicly access Camera.width and Camera.height anymore, so the aspect ratio could be computed with stale data.
Differential Revision: https://developer.blender.org/D9961
Also set default CYCLES_INSTALL_PATH to CMAKE_INSTALL_PREFIX.
By default with a `make cycles` this will build to ${CMAKE_BINARY_DIR}/bin
Differential Revision: https://developer.blender.org/D9961
Using rna iterators in range-based for loops is possible since {rBc4286ddb095d32714c9d5f10751a14f5871b3844}.
This patch only updates the places that are easy to update
without more changes in surrounding code.
Differential Revision: https://developer.blender.org/D10195
The implementation is currently optimized to load animation sequences once
and then quickly scrubbing through them. Later on an option should be added
to optimize for memory usage and only load the current frame into memory.
Currently mesh and curve objects are supported, including support for UV and
vertex color attributes. Missing still is support for arbitrary attributes and
motion blur, as well as better handling of changing topology. Shader assignments
are made using FaceSets found in the Alembic archive.
The animation (and constant) data of the objects inside the Alembic archive is
loaded at once at the beginning of the render and kept inside a cache. At each
frame change we simply update the right socket of the corresponding Cycles node
if the data is animated. This allows for fast playback in the viewport
(depending on the scene size and compute power).
Note this is not yet exposed in the Blender UI, it's a feature that is still under
development and not ready for general use.
Ref T79174, D3089
Procedurals are nodes in the scene that can generate an arbitrary number of
other nodes at render time. This will be used to implement an Alembic procedural
that can load an Alembic file into Cycles nodes. In the future we also expect to
have a USD procedural.
Direct loading of such files at render time is a standard feature in other
production renderers. Reasons to support this are memory usage and performance,
delayed loading of heavy scene data until rendering, Cycles standalone rendering
using standard file formats beyond our XML files, and shared functionality for
Cycles integration in multiple 3D apps.
Ref T79174, D3089
Modifications to triangle shader association were not considered when checking for updates and the associated device data array was not tagged as modified so it was not resent to the device(s).
* tbb::blocked_range moved to a different namespace and since the fix is
non-trivial, remove some unused code that used this.
* Task group priorities are no longer supported. It's unclear if they are
useful at all right now and even set correctly, for now all tasks are equal
priority with TBB 2021.
This optimizes device updates (during user edits or frame changes in
the viewport) by avoiding unnecessary computations. To achieve this,
we use a combination of the sockets' update flags as well as some new
flags passed to the various managers when tagging for an update to tell
exactly what the tagging is for (e.g. shader was modified, object was
removed, etc.).
Besides avoiding recomputations, we also avoid resending to the devices
unmodified data arrays, thus reducing bandwidth usage. For OptiX and
Embree, BVH packing was also multithreaded.
The performance improvements may vary depending on the used device (CPU
or GPU), and the content of the scene. Simple scenes (e.g. with no adaptive
subdivision or volumes) rendered using OptiX will benefit from this work
the most.
On average, for a variety of animated scenes, this gives a 3x speedup.
Reviewed By: #cycles, brecht
Maniphest Tasks: T79174
Differential Revision: https://developer.blender.org/D9555
