[Glamor] [PATCH 1/2] Change the trapezoid render to use VBO

[Chris Wilson]

On Tue, 17 Jul 2012 06:53:41 +0800, junyan.he at linux.intel.com wrote:
> From: Junyan He <junyan.he at linux.intel.com>
> 
>  Because some uniform variables need to be set for every
>  trapezoid rendering, we can not use vbo to render multi
>  trapezoids one time, which have performance big loss.
>  We now add attributes which contain the same value to bypass
>  the uniform variable problem. The uniform value for one
>  trapezoid will be set to the same value to all the vertex
>  of that trapezoid as an attribute, then in FS, it is still
>  a constant.

This still has the problem that it misrenders neighbouring trapezoids,
which is not permitted even in the imprecise specification (and since it
does not conform to the specification of precise rasterisation it should
not be used there either). To get around the former issue with the
current design you still need an intermediate accumulation buffer.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre