Re: what's reason.?
Joaquin Casillas Melendez (jcasilla++at++glup.irobot.uv.es)
Mon, 14 Sep 1998 11:58:46 -0700
Svend Tang-Petersen wrote:
>
> Hi.
>
> A quick guess would be that this is a problem often occurring in
> database modeling
> namely z-fighting (z-buffering).
>
> It occurs if you have modeled polygons which are exactly or almost on
> top of each other.
> The problem then is when the scene gets drawn that the distance to the
> two polygons is the same
> when you take the precision of the z-buffer into account.
>
> So when you're drawing the scene the color which gets chosen is
> depending on the drawing order
> of the polygons and the round off error/comparison with the depth value
> already in the z-buffer.
> This can give the effect of seeing one or the other polygon at random,
> thus the flickering.
>
> There are a couple of ways to get around this:
>
> a) Never model polygons that are exactly on top of each other, but have
> a small offset
> between them.
>
> b) In perfly try to change the range of the z-buffer, by moving the
> Near clipping plane out
> and the Far clipping plane in.
>
Well, there is also another aproach:
c) Take a look at pfLayer nodes if you want to draw coplanar
geometry. It might help to solve the z-fighting problem.
-----------------------------------------------
Joaquin Casillas Melendez mailto:jcasilla++at++glup.irobot.uv.es
LISITT (ARTEC) Phone: +34 6 360 4484
Dept. Electr. & Informatics Addr: Poligono de la Coma s/n
University of Valencia Valencia (SPAIN)
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on Mon Sep 14 1998 - 02:54:25 PDT