In the indirect case we can possibly just adjust the indirect setup code to write the uniform with MI_SRM, if we know where it will be -- so not too awful -- but it is different.
On Sun, Jun 22, 2014 at 1:59 PM, Marek Olšák <mar...@gmail.com> wrote: > That's right. A uniform won't work with ARB_draw_indirect unless you > lower it to direct draws, which would be very bad if it was applied to > all drivers. > > Radeonsi indeed supports BaseVertex and BaseInstance as system values > in the vertex shader. Well, vertex fetching has to be done in the > vertex shader on that hardware, so the system values are kinda > required there. > > Marek > > On Sun, Jun 22, 2014 at 12:27 AM, Chris Forbes <chr...@ijw.co.nz> wrote: >> This will be broken for indirect draws too, and possibly >> performance-crippling to fix there, since we don't have the baseVertex >> value available to shove into a uniform. >> >> On Sun, Jun 22, 2014 at 3:36 AM, Roland Scheidegger <srol...@vmware.com> >> wrote: >>> Am 21.06.2014 03:00, schrieb Ian Romanick: >>>> This patch series fixes bugs in the i965 w.r.t. several uses of >>>> gl_VertexID. OpenGL (desktop and ES) have the following expectations of >>>> gl_VertexID: >>>> >>>> 1. When used with BaseVertex drawing commands, gl_VertexID will include >>>> the value of basevertex. This differens from "the other API," but the >>>> change in OpenGL was based on feedback from application developers. >>>> This only affects OpenGL 3.2+. >>> >>> I don't question this, but note some binary drivers may not agree. There >>> are unforunately lots of man pages around of >>> glDrawElementsInstancedBaseVertexBaseInstance too which state: >>> "The basevertex has no effect on the shader-visible value of >>> gl_VertexID." There's a bug filed about this >>> (https://www.khronos.org/bugzilla/show_bug.cgi?id=932) which is still >>> open though maybe it has all been resolved... >>> (I'll just mention that llvmpipe right now will do d3d10-style vertexID >>> though I guess indeed at some point we need to make it either switchable >>> or implement GL_ARB_shader_draw_parameters so it can be worked around >>> easily in the state tracker.) >>> >>> Roland >>> >>> >>>> >>>> 2. When used with DrawArrays drawing commands, gl_VertexID will count >>>> from the 'start' value instead of zero. This affects OpenGL 3.0+ and >>>> OpenGL ES 3.0+. >>>> >>>> The i965 driver botched both of these for slightly different reasons. >>>> For #1, our hardware was designed with the "other API's" semantic in >>>> mind, so gl_VertexID doesn't include the basevertex value. >>>> >>>> For #2, we implement DrawArrays with a non-zero start index by >>>> reprogramming the array base offset. As a result, gl_VertexID always >>>> counts from zero. >>>> >>>> I suspect other hardware may suffer from one or both of these issues. I >>>> have sent tests to the piglit list to reproduce them. >>>> >>>> To fix both of these issues, the shader needs to know the basevertex >>>> value. A later GL extension, GL_ARB_shader_draw_parameters, adds >>>> gl_BaseVertex and gl_BaseInstance as built-in variables. I believe some >>>> hardware implements these as system values much like gl_VertexID. >>>> >>>> I started this series with the assumption that we could have a >>>> SYSTEM_VALUE_BASE_VERTEX that might come from a uniform. In the end, I >>>> couldn't make that work. I left patch 7 in the series, but we may want >>>> to remove it. >>>> >>>> I added a STATE_BASE_VERTEX uniform instead. >>>> >>>> There is now a lowering pass that converts gl_VertexID to >>>> gl_VertexIDMESA + gl_BaseVertex (backed by a uniform). Some of these >>>> names should probably be changed. >>>> >>>> I have also contemplated adding an extension that exposes the other >>>> semantic for gl_VertexID for applications that actually want that. This >>>> is primarily things that are porting content (or "bridging" content) >>>> from the other API. That, however, can happen later. >>>> >>>> _______________________________________________ >>>> mesa-dev mailing list >>>> mesa-dev@lists.freedesktop.org >>>> https://urldefense.proofpoint.com/v1/url?u=http://lists.freedesktop.org/mailman/listinfo/mesa-dev&k=oIvRg1%2BdGAgOoM1BIlLLqw%3D%3D%0A&r=F4msKE2WxRzA%2BwN%2B25muztFm5TSPwE8HKJfWfR2NgfY%3D%0A&m=E56BlL24I31lr1fFtEsKBJjAprQ%2BQdhUczD1EsQ3dIY%3D%0A&s=2634834afd3400c841ab62f11a9b5350d604592529cfea97f2297c9398c0fd93 >>>> >>> _______________________________________________ >>> mesa-dev mailing list >>> mesa-dev@lists.freedesktop.org >>> http://lists.freedesktop.org/mailman/listinfo/mesa-dev >> _______________________________________________ >> mesa-dev mailing list >> mesa-dev@lists.freedesktop.org >> http://lists.freedesktop.org/mailman/listinfo/mesa-dev _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
