[Mesa-dev] [Mesa3d-dev] r300g: hack around issue with doom3 and 0 stride

[Dave Airlie]

On Sun, Apr 11, 2010 at 9:27 AM, Zack Rusin <zackr at vmware.com> wrote:
> On Saturday 10 April 2010 18:44:27 Luca Barbieri wrote:
>> > r300g: hack around issue with doom3 and 0 stride
>> >
>> > This is most likely a bug in the mesa state tracker, but do the quick
>> > hack for now to avoid the divide by 0.
>>
>> This is not a bug: stride 0 means that the vertex attribute is
>> constant for all vertices.
>
> Right, it's how our vbo code handles cases like
> glBegin(primitive);
> glColor4f(...);
> glVertex(...);
> glVertex(...);
> glVertex(...);
> glEnd();
>
>> Thus, the patch is not likely to be correct: you should instead either
>> program stride 0 to the hardware if supported, or fetch the vertex
>> attribute with the CPU
>
> Dave, jfyi, i implemented this a long time ago in svga, just search for
> zero_stride in there (svga_hw_update_zero_stride in particular), you should be
> able to almost simply copy&paste that code.

Wierdly we've never hit this divide by zero with any piglit test or any games
except doom3, I know some of our tests use the above code, so I suspect
this stride 0 vbo isn't one of the above. I could be wrong of course.

Dave.

>
> z
>