John Carmack wrote:
>
> >This is done inside glide, mesa doesn't see it. I was wondering about
> this for
> >the mga driver - do you have the magic incantations to build the displaced
> >vertices for the two triangles? I don't see any way to avoid taking
> 1/sqrt(area)
> >to get the increments. It's the square root I'd like to avoid...
>
> Fat line joining is rather non-trivial. I think the OpenGL spec has an
> exact description of what is supposed to be done.
>
> For textured single unit lines, I think just drawing from a surrounding one
> unit box corner at each vertex would work fine, although even that might
> have some artifacts with blending enabled.
I hadn't even considered fat lines (or stipples). I was just thinking about how
to define the two triangles which define the line - for points it's easy as the
offsets will be axis-aligned, but for lines I'm not sure you can get away with
just adding and subtracting .5 to get the corners of the thin quad.
The other nasty thing is interaction with hardware culling, though providing you
never set up the card to do 'GL_FRONT_AND_BACK' culling it can be worked around.
Most cards don't implement this anyway, it seems.
I'd like to prototype this at the driver level first (ie inside mga), and hoist
it to Mesa once it's working. I'll try & get something running there for points
& lines tonight.
I don't know if this stuff will make 3.1 - I think the consensus is that we are
fixing bugs & no more for now.
Keith
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