another zbuffer question

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John C Vanderburgh (jvanderb++at++afit.af.mil)
Wed, 19 Oct 1994 17:12:39 -0400


Hey all,
  Another z-buffer question...

I'm using a 32-bit zbuffer on an Onyx RE2 for my application.
According to the "getgdesc" routine, my min and max z-buffer
values are:

   GD_ZMIN = -2147479552
   GD_ZMAX = 2139095040

Based on those values, what is the "depth resolution" that
I should have in my application? The far clipping plane
of my (perspective) viewing frustum is at 35,000,000 units
from the eyepoint. (Remember, I'm modeling space...)
Why do I get z-buffer problems when
that's no where near my GD_ZMAX value? I know the GL Programming
Guide says,

"The z-buffer contains a finite number of integers,
each with a limited range of values that can be used to compare
against the z value of the incoming pixel. You can enhance the
resolution of the z-buffer by setting the near and far values
as close together as possible."

But what does "limited range of values" mean??
Specifically, how does the hardware use those 32 bits in the z-buffer?

Thanks for any help,

John Vanderburgh
AF Institute of Technology
Wright-Patterson AFB, OH


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