Re: [Mesa3d-users] Antialiased Polygons Show Lines

[Brian P. <br...@va...>]

michael wrote:
> 
> I've searched around, yet have found no solution to what I am
> experiencing.
> 
> Whenever I enable GL_POLYGON_SMOOTH, the polys are definitely
> anti-aliased, however, I see the triangular lines outlining the polys
> (also anti-aliased when the depth buffer is disabled).  The lines are
> the color of glClearColor like there are holes.  Even with the simplest
> case of 1 gluSphere this happens.
> 
> I'm currently running Mesa-3.4.1, no hardware accel, linux 2.2.18.
> The same thing happened with last night's cvs snapshot, and a 3.3
> version of Mesa.
> I've also rendered it in both a gtkglarea context and an
> OSMesaCreateContext.
> Blending func is GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA.
> 
> It's all working, just can't get rid of the lines.

Try glBlendFunc(GL_SRC_ALPHA_SATURATE, GL_ONE) and render your
polgyons in front-to-back order.  This also requires a destination
alpha buffer.  See the OpenGL Programming Guide for details.  You
can find it on-line if you search for it.

Unfortunately, it's often hard to meet these requirements, but
that's what you have to do if you want the correct results.

If you're working with 2-D objects, like character glyphs made out
of non-overlappying polygons, you can try glBlendFunc(GL_ONE, GL_ONE).
Then the coverage of pixels along shared edges will sum to 100%.

Finally, note that GL_POLYGONS are always broken down and processed
as triangles.  That's why you're seeing internal edges.

-Brian