Yes, but it seems suboptimal, incurring overhead on every rendered pixel. Another way that I just realized would be to convert a texture to BGRA the first time it's rendered to.
In contrast to the shader solution that has only a one-time overhead. Is this a stupid idea for any reason? Wladimir On Feb 3, 2017 11:00, "Christian Gmeiner" <christian.gmei...@gmail.com> wrote: > Hi, > > 2017-02-03 10:56 GMT+01:00 Wladimir J. van der Laan <laa...@gmail.com>: > > Hello, > > > > With the Etnaviv driver we're running into an issue: The GPU can only > render *to* > > BGRA formats. It can however render *from* BGRA as well as RGBA textures. > > > > I know that the OpenGL ES standard allows drivers to choose what order > is most > > appropriate when being asked for "GL_RGBA" textures. So back when > etnaviv supported > > only BGRA, Mesa automatically picked that and everything was okay. > > > > However a recent patch added support for RGBA formats in > etnaviv_format.c. > > > > Now, Mesa creates a real GL_RGBA texture when this is requested. This is > all > > and well for rendering, however for anything using FBO to render to > textures > > this is a problem. > > > > Qt, for example, is assuming it can attach the GL_RGBA texture to a FBO. > This > > fails now that GL_RGBA textures are really GL_RGBA, and it doesn't > handle that > > error to fall back to something else so rendering issues ensue. > > > > I'm not sure how to handle this: > > > > - The quick fix would be to revert the RGBA formats patch, but the > hardware > > supports rendering *from* RGBA textures fine so this would be throwing > away a > > feature. > > > > - Another way would be to try to fix Qt to cope with this, and try e.g. > GL_BGRA_EXT > > when it wants to render to a texture. Burdening the client code with > this seems > > unintuitive to me. > > > > - Another hack would be to implement shader variants, and swap R/B in > the pixel > > shader to emulate rendering to RGBA. > > > > In my opinion shader variants are the way to go - almost every driver > make use of them to > 'fix' such issues. > > greets > -- > Christian Gmeiner, MSc > > https://www.youtube.com/user/AloryOFFICIAL > https://soundcloud.com/christian-gmeiner >
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