Re: Z-Buffer, fog, and post processing

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Rick Weyrauch (rweyrauch++at++camus.paradigmsim.com)
Fri, 20 Sep 1996 04:37:01 -0500

On Sep 19, 5:02pm, Jude Anthony wrote:
> Subject: Z-Buffer, fog, and post processing
> I'm working on a simulation involving large databases and terrain.
> For reference, our clipping planes are about 20 nautical miles apart
> (some 37,000+ meters). Unfortunately, all the data doesn't fit
> between the clipping planes, so when we move from one end of the
> terrain to the other, mountains appear to extrude themselves from
> an invisible play-doh press.
>
> We would like to have the mountains appear gradually out of haze. We
> tried to implement this using fog, but the linear fog near and far
> ranges don't do what you would expect them to do (nor what the man
> pages say they should do). I'm interested in examining the Z-buffer
> after each draw frame and blending the color of far-off pixels with
> the sky color, thus implementing a nice haze effect.
>
> I tried the man pages, but I can't find any reference to Z-buffer,
> let alone reading a Z-buffer. Nor is there anything intuitive for
> changing the color of a single pixel. Anybody know where I can find
> some example code for this kind of effect?
>
> We're using an Onyx with IR2.
>
> Thanks,
> Jude Anthony
> jude++at++p3.enzian.com
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>-- End of excerpt from Jude Anthony

Jude,

Take a look at spline fog (PFFOG_PIX_SPLINE, and pfFogRamp). A spline fog ramp
can be set up so that objects near the far clipping plane will fogged and
eliminate the "play-doh press" phenomenon.

Rick

-- 


Rick Weyrauch				voice: (214) 960-2301
Paradigm Simulation Inc.		fax:   (214) 960-2303
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