Re: Using wireframe to fake antialiasing

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Angus Dorbie (dorbie++at++sgi.com)
Thu, 21 Jan 1999 14:38:49 -0800

Brennan McTernan wrote:
>
> I have been watching this thread because I have also done this with some
> success. After painful experience, having the client buy a machine with
> multisampling is the way to go.

This is a CHEAP approach for antialiasing on a low end system. Buying an
hardware aa machine is not an option at most price points where you use
this hack to improve a solution.

>
> I have two other thoughts about this. First, hidden deep within the OGL
> documentation is a discussion about the way polys and lines are drawn.
> Check out glPolygonOffsetEXT. You can't get around your lines breaking up
> at some places without looking at the factor and bias parameters of this
> call. A second thought is change z buffer testing to less-than-or-equal,
> and then draw your polygons in wireframe. Don't forget to put the zbuffer
> test back.

Polygon offset is important where you have poly colors describing edges
within an object, if the object is just textured then zfighting between
lines and polys is unimportant because they match perfectly. Less than
or equal is an acceptable test even for permanent rendering, in fact
it's probably the most used.

CHeers,Angus.

-- 
"Only the mediocre are always at their best." -- Jean Giraudoux


For advanced 3D graphics Performer + OpenGL based examples and tutors:
http://www.dorbie.com/

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