Brennan McTernan (brennan++at++mte.com)
Thu, 21 Jan 1999 16:14:43 -0500
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.
On Wed, 20 Jan 1999, Angus Dorbie wrote:
> Scott Herod wrote:
> >
> > Ahhh. So by simply doing a straight wireframe on a second
> > (or first) pass, I'm getting each edge twice and with alpha
> > blending on, I'm doubling the alpha values?
>
> Youre blending twice but you probably have some z fighting on the edges
> travelling in opposite directions so it's a little more complex.
>
> >
> > What you suggest is essentially what I ended up doing by hand
> > in an example that I worked up. I've got lighting to work
> > with materials but texgen is slightly (but noticably) off so
> > edges are visible. Straight textures worked well.
>
> Texgen or texture modulation?
>
> This should be very close, on IMPACT when I did this there was no
> noticeable edge, perhaps you have a lighting(surface normal) mismatch.
> It is unlikely that the problem would be with texture and extremely
> unlikely that texgen would be the culprit.
>
> >
> > It sounds like it would be best to just tell people that they
> > will need a machine with hardware multi-sampling in order to
> > smooth generic models.
>
> Absolutely not, nobody said this technique didn't involve some overhead,
> both in engineering and scene complexity.
>
> People have been using this since VGXT and customers are happy with the
> results when they implement this. I agree that if you wnat an easy life
> and/or correctly weighted samples then you need a true aa solution like
> a multisample buffer. When I did this using MultiGen is was very
> straightforward.
>
> Setting non occluding transparency (masking zwrites) on the wireframe
> models is also desirable.
>
> 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/
> =======================================================================
> List Archives, FAQ, FTP: http://www.sgi.com/software/performer/
> Submissions: info-performer++at++sgi.com
> Admin. requests: info-performer-request++at++sgi.com
>
This archive was generated by hypermail 2.0b2 on Thu Jan 21 1999 - 13:14:51 PST