The Blender/Cycles XYZ color space has a D65 white point instead of E, and
this was not correctly accounted for both in the OpenColor config reading code
and the bundled config.
This meant that since the OpenColorIO v2 upgrade, the Linear ACES color space
was not working correctly, and other OpenColorIO configs defining
aces_interchange were not interpreted correctly.
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
Change to false color are based on artist feedback:
* Even 2.5 EV differences down to -10 EV.
* Even 2.167 EV differences up to +6.5 EV.
* Slightly below middle grey biased toward cyan.
* Slightly above middle grey biased toward yellow.
* Converts to nonlinear luma for more accuracy.
* Replace Log view transform with Filmic Log.
* Remove Rec.709, DCI-P3 displays that were incomplete and outdated.
* Remove outdated RRT and Film transforms, replaced by Filmic.
* Remove camera responsive curves that don't work with HDR colors.
* Rename Default view transform to Standard.
We're breaking compatibility now for 2.80, so that we can add future
improvements on a clean config.
Part of the code was contributed by George Vogiatzis in D4782.
Differential Revision: https://developer.blender.org/D4900
* Use simple default view transform for color pickers, as Filmic does not work
well for all types of colors. We better handle this with an option and tagging
of colors as emissive or albedo like.
* For solid/workbench we also no longer use Filmic, as there is not enough contrast
and it's not really needed since this is not physically based lighting.
* For lookdev always take into account the view transform and look. Other view
settings like exposure are only taken into account if scene lighting is used,
since these are often dependent on scene light intensity.
Fixes T61022, T57649, T59363.
In 2d655d3 the color picker was changed to use display space HSV values.
This works ok for a simple sRGB EOTF, but fails with view transforms like
Filmic where display space V 1.0 maps to RGB 16.292.
Instead we now use the color_picking role from the OCIO config when
converting from RGB to HSV in the color picker. This role is set to sRGB
in the default OCIO config.
This color space fits the following requirements:
* It is approximately perceptually linear, so that the HSV numbers and
the HSV cube/circle have an intuitive distribution.
* It has the same gamut as the scene linear color space.
* Color picking values 0..1 map to scene linear values in the 0..1 range,
so that picked albedo values are energy conserving.
This ignores the scene color managment view settings for solid mode and
lookdev when not using scene lights and world. The scene settings are
intended for tweaking renders and should not affect studio lighting and
matcaps.
There may be cases where a simple sRGB transform is better than Filmic
and we could add configuration for this. Not sure if it really matters
and it may be better if we just assume matcaps and studiolights are all
created for one view transform.
Differential Revision: https://developer.blender.org/D3569
I've limited it to just the RGB<->XYZ stuff for now, correct image handling is the next step.
Reviewers: brecht, sergey
Differential Revision: https://developer.blender.org/D3478
* "Filmic" and "False Color" view transforms added (sRGB display device only).
* "Very Low/Low/Base/High/Very High Contrast" looks added.
* Added filtering so that Filmic only shows look names prefixed with "Filmic - ".
Filmic Dynamic Range LUT configuration created by Troy James Sobotka with
special thanks and feedback from Guillermo, Claudio Rocha, Bassam Kurdali,
Eugenio Pignataro, Henri Hebeisen, Jason Clarke, Haarm-Peter Duiker, Thomas
Mansencal, and Timothy Lottes.
Differential Revision: https://developer.blender.org/D2659
Previously converting from linear space to SRGB was doing rather
slow inverted 1D lookup. Adding explicit inverse LUT gives 20%
speedup of OpenGL render.
Next question is: why do we even bother with sRGB conversion here,
OpenGL is already in the proper space so in theory we can avoid
quite some color space conversions. In any case, having this case
optimized in nice anyway.
* Reorder list a bit to put brands together
* Move looks menu below views
* Rename camera_response to film_response folder, to make clear that these
are photographic film types, not camera models
This commit implement's OCIO's Looks idea which
is about applying some color correction on the
buffer before it get's affected by a display
transform.
This is mainly used to modify images in an
artistics way.
Currently we've got looks generated from film
response curves for all sorts of cameras.
Patch by both of me and Brecht.
- Sequencer preview was clamping float buffers
- ACES color space wasn't correct, was noticeable when
applying display processor from linear space to display.
- Extended sRGB LUT to sRGBf from nuke-default config.
Makes sequencer behave much better in sRGB space.
have no effect on the end result, because it is only an intermediate space and
scene_linear was already set to Linear. It does avoid some unnecessary matrix
transforms which should be a bit faster, and it makes it more clear what's
happening.
This commit integrates support of OpenColorIO library into build systems.
It also contains C-API for OpenColorIO library which could be used by Blender.
CMake has got find rules familiar to OpenImageIO's one which makes it easier
for build system to find needed libraries and includes. Scons only could use
explicitly defined paths to libraries and includes.
C-API would be compiled and Blender would be linked against C-API and OpenColorIO
but it wouldn't affect on Blender behavior at all.
OpenColorIO could be disabled by setting up WITH_OCIO to Off in CMake and
setting WITH_BF_OCIO in Scons.
