On Monday 17 October 2011 15:38:18 Henri Verbeet wrote:
I think the "gl_" prefix is somewhat questionable since the format being compressed or not is a property of the D3D format, it doesn't depend on what GL format we use, at least in the way the flag is currently used. You can change the meaning of the flag to be specific to the GL format, but then you'd have to set it in the format_texture_info[] table.
The idea is to mark formats that need glCompressedTexImage2D instead of glTexImage2D, so format_texture_info sounds about right.
/* Block-based formats can't be rendered to with FBOs even if GLaccepts them + * (e.g. WINED3DFMT_YV12, which is just a GL_ALPHA texture). Even fragment shaders + * can't account for that if a block is partially drawn.
There's no such restriction on the GL side, the internal format just has to be color-renderable. The reason we can't render directly to these is because there a fixup associated with the format, but that has nothing to do with either being FBO-attachable or being block-based, and applies to e.g. P8 as well.
The fixup is a separate issue. We can write to formats with fixups just fine if the input is in the correct format or we have a shader that can convert TO that format. The problem with the blocks is that if one pixel is modified the entire block may have to be modified, and we can't do that even with shaders. So we can't blit to e.g. YUY2 surfaces even if the input is YUY2 as well and the underlying luminance-alpha textures may be fbo attachable.
But following the logic of the compressed flag above, that should also be part of the format defintion in format_texture_info[]. When a native GL format is used(e.g. GL_APPLE_ycbcr_422 or standard s3tc) the check if the format is FBO attachable should be used. I can also move this to a separate patch.
On a somewhat related note, Windows 7 has overlay d3dx9 swapchains. The SDK claims that those may support YUV primaries, but according to http://www.virtualdub.org/blog/pivot/entry.php?id=282 and a follow-up post HW drivers only support RGB formats.