From: Brickley, Jeff (bricklej++at++newtec.wsmr.army.mil)
Date: 01/25/2001 06:37:21
The Z-buffer depth is usually handled by the driver to your
graphics card, however, Performer is higher level based on
OpenGL, and OpenGL has depth issues that most new
programmers are not aware of (and the rest of us forget
about it until someone asks). The ratio from near to far
results in the which bit is tested in depth testing for a
particular triangle/object and the bits are somewhat biased
toward the near clipping plane. The detailed information of
the reasons for this are at the OpenGL faqs page (
http://www.opengl.org/developers/faqs/technical/depthbuffer.
htm#dept0045 ) at www.opengl.org however, the net result is
this: adjust the near clipping plane out as you extend the
far clipping plane. I had this problem a number of years
ago, because I was running 0.1/10000000 when I was
exo-atmosphere and the result of z-fighting was frightening,
but 8000/10000000 looked pretty decent as long as you
weren't trying to look at something only 8km away in orbit
with you....
just me,
Jeff
======================================
Jeffry J. Brickley
<jbrickley++at++programmer.net>
Senior Software Engineer
SRS Information Services
Building 1554
PO Box 398
White Sands Missile Range, NM 88002
phone: 505-678-3557
fax: 505-678-7985
======================================
-----Original Message-----
From: Harry Overs [mailto:hovers++at++dera.gov.uk]
Sent: Thursday, January 25, 2001 2:57 AM
To: info-performer++at++sgi.com
Subject: Z buffer
Quick newby question:
How easy is it to increase the number of Z buffer bitplanes
used in my
performer(2.3) app running on Linux (RH6.1) ?
I am having trouble with roads flickering on my terrain, and
have been told
that increasing Z buffer can help. Thanks
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