[Mesa-dev] Gallium API questions

[Brian Paul]

Keith Whitwell wrote:
>> We currently allow partial specification of position, requiring only
>> (x, y) and filling in z as 0 and w as 1 if missing. Is that still
>> valid? Similarly, colors may be specified as (r, g, b) triplets with
>> no alpha, and alpha defaults to 1. Is that still valid, or are there
>> changes further up the API that make this not needed?
> 
> I don't think either of those statements are true, except for the
> special case that in the fragment shader *only* position.z is writeable
> - ie the x,y coordinates are already fixed, and there is no meaning to
> writing the position.w coordinate once you're inside the fragment
> shader.

I believe Corbin was referring to incoming vertex data in the case of 
glVertex2f and glColor3f, for example.

I need to update the docs with fragment shader z-write...

-Brian