On Thu, Dec 11, 2008 at 06:49:44PM +0100, Philipp Klaus Krause wrote: > Brian Paul schrieb: > > >>> 1. Has anyone started a similar work? How can I contact him? > >> Well, we already have the similar GL_EXT_paletted_texture in Mesa. > > > > That's quite a bit different from OES_compressed_paletted_texture. > > > > In OES_compressed_paletted_texture the palette is encoded at the start > > of the texture data itself. In GL_EXT_paletted_texture a separate color > > table is specified and potentially shared by all index-format textures. > > > > One could easily convert OES_compressed_paletted_texture images into > > ordinary RGB textures at some point in Mesa or the driver. > > To me it seems GL_EXT_paletted_texture is more powerful, but both are > about paletted textures. So it could make sense (until a driver wants to > support hardware that can do GL_OES_compressed_texture but not > GL_EXT_paletted_texture) to implement OES_compressed_paletted_texture on > top of GL_EXT_paletted_texture (instead of on top of ordinary RGB textures).
In hardware, nobody supports the full range of GL_EXT_paletted_texture, and nobody ever really did. The problem is multitexture. Each texture can have a separate palette, but all hardware that I have ever seen has only one texture palette. This ultimately leads to a giant pile of suck. The problems are compounded by the ability to change the palette at any time between rendering. GL_OES_compressed_paletted_texture has the same problem with a single hardware texture palette. However, once a texture is set, it's palette cannot change. This greatly simplifies things when a driver gets into a situation where multiple palettes are needed. It can convert one of the textures from paletted to RGBA and keep that converted copy forever.
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