On Fri, Mar 12, 2010 at 12:19 PM, Maciej Cencora <m.cenc...@gmail.com> wrote: > Hi all, > > I've got some questions regarding FBOs in mesa. I hope you'll be able to > answer at least some of them. > > GLcontext structure holds pointers to 4 gl_framebuffers (DrawBuffer, > ReadBuffer, > WinSysDrawBuffer, WinSysReadBuffer) and one to gl_renderbuffer > (CurrentRenderbuffer). gl_framebuffer struct contains amongs other fields: > _ColorDrawBuffers[], _ColorReadBuffers, _DepthBuffer, _StencilBuffer. > Now having in mind that r300 wraps all gl_renderbuffers and gl_texture_object
Do you mean that r300 subclasses gl_renderbuffer and gl_texture_object? That's what I think you mean. The term "wrapping" has a special meaning for renderbuffers (see below). > (they contain HW buffer objects that I'm interested in), what is the proper > way > to get to read and draw buffers? The current "read" framebuffer is at ctx->ReadBuffer. The current drawing framebuffer is ctx->DrawBuffer. Then, if you're reading _colors_ the renderbuffer to use is ctx->ReadBuffer->_ColorReadBuffer. If you want to read _stencil_ values, it would be ctx->ReadBuffer->_StencilBuffer. Similarly for Z/depth, etc. To draw to color buffers (there may be more than one) you'll want ctx->DrawBuffer->_ColorDrawBuffers[]. For stencil it's ctx->DrawBuffer->_Stencil, etc. Renderbuffers typically correspond to a region of video memory. How that works is driver-dependent. > What operations use ctx->_ReadBuffer besides glReadPixels,glCopyPixels and > glCopyTex(Sub)Image? glCopyColorTable and maybe some other obscure functions. You got the main ones. > What operations use ctx->_DrawBuffer besides rendering operations? > (glBegin/glEnd, glDrawElements, glDrawArrays, ...) That's basically it, plus glClear. > Am I correct that for ctx->_DrawBuffer field _ColorReadBuffer is unused, and > for > ctx->_ReadBuffer _ColorDrawBuffers is unused? No, they're used - see above. The _ColorReadBuffer field depends on the glReadBuffer() call. The _ColorDrawBuffers[] pointers depend on the glDrawBuffer() and glDrawBuffersARB() functions. It's important to understand the heirarchy of gl_framebuffers and gl_renderbuffers. Each framebuffer object has a collection of renderbuffers. Renderbuffers may also act as wrappers for gl_texture_object when doing render to texture. In this case, the renderbuffer acts as a 2D view into a level/slice/face of a texture object. Also, we have special depth/stencil renderbuffers which wrap combined depth/stencil buffers. See main/depthstencil.c That's mainly for software rendering, though. -Brian ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Mesa3d-dev mailing list Mesa3d-dev@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mesa3d-dev
