On Tue, May 20, 2014 at 6:20 PM, Marek Olšák <mar...@gmail.com> wrote: > On Tue, May 20, 2014 at 11:04 PM, Ilia Mirkin <imir...@alum.mit.edu> wrote: >> On Tue, May 20, 2014 at 4:51 PM, Marek Olšák <mar...@gmail.com> wrote: >>> On Tue, May 20, 2014 at 9:58 PM, Ilia Mirkin <imir...@alum.mit.edu> wrote: >>>> Hello, >>>> >>>> I attempted doing this a while back, before I really understood what >>>> was going on. I got some advice that went totally over my head, and I >>>> dropped the issue. I think I'm much better-prepared to tackle the >>>> issue this time around. >>>> >>>> To recap, nv30 (and nv40) hw can't handle certain color/depth format >>>> combinations. Specifically, a 16-bit color format must be paired with >>>> a 16-bit depth format, and a 32-bit color format must be paired with a >>>> 32-bit depth format (well, Z24S8). This HW also can't handle different >>>> per-attachment sizes, and also the "linearity" of all the attachments >>>> must be the same. (Whether a surface is linear or not is _generally_ >>>> dictated by its w/h, but not always -- POT textures can sometimes end >>>> up allocated linearly by e.g. the ddx, or something else.) The >>>> different sizes are handled by not exposing ARB_fbo. However the rest >>>> of the cases remain. >>>> >>>> Now that I kinda understand how things are structured, I was thinking >>>> of doing the following: >>>> >>>> When rendering (i.e. draw_vbo & co) and the fbo has changed (and has >>>> one of the problems above), I would instead put in a temporary texture >>>> as the depth attachment. Before actually drawing, I would blit from >>>> the real target texture into the temporary texture, and then when >>>> rendering is done, blit back from the temp texture back into the >>>> target. This deals with the target texture getting modified between >>>> draws with various blits/mapping/whatever. >>>> >>>> This means that you'll only get 16 bits of depth even if you ask for >>>> 24 with a 16-bit color format, but the alternative seems too >>>> complex/costly. >>>> >>>> So there are a few questions from this approach: >>>> >>>> 1. Where do I get the temporary texture from? (And more importantly -- >>>> when... what happens if allocation fails?) >>>> >>>> 2. Having to blit the depth texture back and forth on every draw seems >>>> _really_ wasteful... anything I can do about that? >>> >>> You can do that in set_framebuffer_state. When binding, blit to a >>> depth buffer which matches the colorbuffer format. When unbinding, >>> blit back. >> >> set_framebuffer_state doesn't allow an error to be returned. Should I >> just print a warning and move on? > > Yes, because you have no other choice. > >> >> I guess I'm still not 100% on all the terminology -- what do you mean >> exactly by bind/unbind? Do you mean the transfer_map/unmap stuff? So >> basically I would blit once on set_framebuffer_state, and then blit >> back and forth on resource map/unmap, and only ever render to the >> "temporary" buffer without worrying about blitting wihle rendering? > > "bind" is when a buffer is set, "unbind" is when the buffer is unset. > set_framebuffer_state unbinds the current framebuffer and binds a new > one. > > transfer_map/unmap must use the resource which contains the latest > data, there is no doubt about that. > > If there are no transfers, you only have to do the blits between > 32-bit and 16-bit in set_framebuffer_state, because that's the only > place where the framebuffer is changed.
OK, I see. That makes sense, I think. So I just have to be careful with the transfers to make sure to blit things back first (or maybe I don't even have to do that, haven't checked the transfer api), similar for blit. And I'll need to turn off ARB_buffer_storage. -ilia _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
