Re: Using wireframe to fake antialiasing

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Angus Dorbie (dorbie++at++sgi.com)
Wed, 20 Jan 1999 14:41:27 -0800


Scott Herod wrote:
>
> Has anyone been able to draw an object's wireframe on top
> of the object and fake antialiasing? While I can do it if
> I build the edges myself, I have not been able to get two-pass
> drawing, once with the object and once with it's wireframe,
> to work. Any suggestions would be appreciated.
>
> Thank you
> Scott Herod
> scott++at++evt.com
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Yes I did this for the UK M.O.D. Rapier fire trainer visual.

One thing you have to watch is that each edge should be drawn once, you
don't get this just drawing a wireframe rep of the same model. Typically
every edge will be drawn twice. So it's best if you have 2 versions of
your model. One solid and the other wireframe but with half the polys so
each edge exists once. The other thing you need to watch is that the
state on the wireframe model matches the state on the poly model exactly
including texture and surface normals. To do this in MultiGen make the
poly model first and shade, then the very last thing you do is copy this
model and delete half the polys so each edge only has one poly adjacent
(you can only approximate this) then you set the draw mode to wireframe
then use pfAntialias to turn on antialiasing (which will smooth the
lines only on a low end system but that's what you need.

If you have any problems I can send you a sample model which implements
this.

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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