Cycles now uses the color space on the image datablock, and uses OpenColorIO
to convert to scene linear as needed. Byte images do not take extra memory,
they are compressed in scene linear + sRGB transfer function which in common
cases is a no-op.
Eevee and workbench were changed to work similar. Float images are stored as
scene linear. Byte images are compressed as scene linear + sRGB and stored in
a GL_SRGB8_ALPHA8 texture. From the GLSL shader side this means they are read
as scene linear, simplifying the code and taking advantage of hardware support.
Further, OpenGL image textures are now all stored with premultiplied alpha.
Eevee texture sampling looks a little different now because interpolation
happens premultiplied and in scene linear space.
Overlays and grease pencil work in sRGB space so those now have an extra
conversion to sRGB after reading from image textures. This is not particularly
elegant but as long as engines use different conventions, one or the other
needs to do conversion.
This change breaks compatibility for cases where multiple image texture nodes
were using the same image with different color space node settings. However it
gives more predictable behavior for baking and texture painting if save, load
and image editing operations have a single color space to handle.
Differential Revision: https://developer.blender.org/D4807
This patch adds a new "Use Alpha" option on image empties to avoid ordering
issue of reference images.
If ordering is not important, "Use Alpha" can be enabled to provide
transparency and alpha blending support.
Support for showing images in background/foreground and only in perspective/orthographic view.
Internally the depth of the image is modified in the fragment shader by setting `gl_FragDepth` explicitly.
The UI still needs some work to improve usability, see D3863 for details.
Currently there is one duplicated function, not sure how to best deduplicate it yet. (`is_image_empty_visible`)
Reviewer: fclem, brecht, campbellbarton
Differential Revision: https://developer.blender.org/D3863
