Cycles: Correct sRGB conversion for interpolated textures.
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Authored by Stefan Werner (swerner) on Sep 18 2019, 5:07 PM.

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Reviewers

Brecht Van Lommel (brecht)
Lukas Stockner (lukasstockner97)
Sergey Sharybin (sergey)

Summary

Conversion from sRGB->linear must happen before texure interpolation.
Previously, compress_as_srgb was a flag of the image node and
the node code did the conversion after the filtered lookup.
Now it's saved in the texture info and conversion happens before
the lookup filter. We can now also leverage GPU color space
conversions.

Fixing T69982

Diff Detail

Repository

rB Blender

Branch

cycles_srgb_texture_fix

Build Status

Buildable 5016
Build 5016: arc lint + arc unit

Event Timeline

Stefan Werner (swerner) created this revision.Sep 18 2019, 5:07 PM

Harbormaster completed remote builds in B5014: Diff 18332.Sep 18 2019, 5:07 PM

Stefan Werner (swerner) edited the summary of this revision. (Show Details)Sep 18 2019, 5:08 PM

Stefan Werner (swerner) added reviewers: Brecht Van Lommel (brecht), Lukas Stockner (lukasstockner97), Sergey Sharybin (sergey).

Stefan Werner (swerner) added a project: Cycles.

Stefan Werner (swerner) added a subscriber: Cycles.

Cleanup: Whitespace

Harbormaster completed remote builds in B5016: Diff 18334.Sep 18 2019, 5:11 PM

Note that there's one case where the color space conversion still happens in the wrong place, that is when OSL is enabled and reading external textures. OpenImageIO's TextureSys is loading 8 bit sRGB textures without color transform and calculates temporary mip maps and any interpolations in the wrong color space.

Code seems fine, but render tests with 16bit images seems to be missing sRGB to linear conversion.

This revision now requires changes to proceed.Sep 19 2019, 1:39 PM

Brecht Van Lommel (brecht) added inline comments.Sep 19 2019, 1:55 PM

intern/cycles/render/nodes.cpp
399	This should be `u_colorspace_srgb`, and then the OSL code should somehow handle that builtin colorspace. We can't assume that the OCIO configuration contains a colorspace named "sRGB", for example the ACES one does not.