Re: [Algorithms] Bullets on walls

[Stephen J B. <sj...@li...>]

On Fri, 21 Jul 2000, Neal Tringham wrote:

> 
> Giovanni Bajo <ba...@pr...> writes:
> > In DirectX, there is a ZBIAS stuff that let you set a priority order
> > (integer) when Z matches. It is a renderstate. But looking at the caps, it
> > is not supported in every boards I have tried. I heard it is an old
> thingie
> > of first Voodoo boards.
> 
> Yes, the support for zbias seems to be rather inconsistent.
> 
> > I had not found something similiar in OpenGL.
> 
> You may want to look at the 1.1 glPolygonOffset function.
 
In OpenGL (and presumably in D3D also), you can fake a polygon
offset by moving the near clip plane a tiny bit between drawing
the 'base' and 'decal' polygons.  This (in effect) changes
the "meaning" of all the numbers currently stored in the Z
buffer - so they represent a distance that is a little further
away than than they did when they were originally rendered.
In effect, this moves the entire scene backwards a little bit.

You need to experiment a bit with how much to move it - but
it's a trick that does work on ALL hardware.

Steve Baker                      (817)619-2657 (Vox/Vox-Mail)
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