ARB_buffer_storage doesn't have anything to do with framebuffers. Marek
On Wed, May 21, 2014 at 2:27 AM, Ilia Mirkin <imir...@alum.mit.edu> wrote: > 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
