Dnia sobota, 13 marca 2010 o 01:10:01 Brian Paul napisał(a): > 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).
Yes, r300 subclasses these structs (and additionally wraps texture objects with renderbuffers). > > > (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. That's what I'm doing, but sometimes it happens that ctx->ReadBuffer- >_ColorReadBuffer is NULL (see drivers/dri/radeon/radeon_tex_copy.c). Is this a legal situation? What should I do then if user requested glCopyTexImage or glCopyPixels? > > 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. > I still don't get it. I see a reason in using _ColorReadBuffer in context of ctx->_ReadBuffer but not in context of ctx->_DrawBuffer (and similarly for _ColorDrawBuffers). Thanks for explanation, Maciej > > 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
