[Bf-committers] OpenGL sRGB

Alberto Torres kungfoobar at gmail.com
Sun Jul 28 11:32:40 CEST 2013

Shader code already has functions for converting from/to sRGB, and it's in
the generated shaders unless you disable sRGB both in textures and output
color space. Maybe there's something wrong (e.g. is it converting
sRGB->linear twice when reading a texture?). I make heavy use of the
generated shaders in my engine, so I'll have to investigate this...

2013/7/28 Jason Wilkins <jason.a.wilkins at gmail.com>

> OpenGL has the ability to automatically convert colors to the sRGB color
> space when writing them to the framebuffer and also to read from textures
> in a mode that treats the texture as being in sRGB space.
> Since I've converted GHOST to use GLEW in order to load WGL extensions I
> was thinking it would be easy to go ahead and enable sRGB frame buffers as
> an option (sRGB textures could come when I'm writing shaders later).
> sRGB can be selectively enabled/disabled as you draw.
> It should be off for drawing the UI and other elements whose colors were
> selected by the user by looking at how they look on a computer monitor.
> It should only be on for elements like lit polygon models in the viewport
> so that the lighting computations final result is gamma correct.
> But elements in the viewport like the grid floor, wireframes, outlines,
> etc. should also not be rendered in sRGB because they are also UI elements.
> This leaves images like textures, previews, and render results.
> If an image is a jpg or something that has no color correction then can I
> assume it is already in sRGB and doesn't need correction?
> And if an image does have color correction information I can assume that
> Blender has already taken steps to make sure it is in sRGB?
> The leaves me thinking that the only place where Blender is not sRGB
> correct is when drawing lit 3D models to the viewport.  So it should be
> fairly easy to enable that.
> It also seems that when reading textures almost all of them will be in
> sRGB, so special shader code will be needed to map them to linear inside of
> shaders.  However, since it is so rare for shaders to be gamma correct,
> this might actually result in strange looking results to people used to
> incorrect lighting computations.
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