Re: Axial billboards, but po

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John C Vanderburgh (jvanderb++at++afit.af.mil)
Thu, 29 Sep 1994 15:08:51 -0400


Hey all,
  In my Performer application, I'm rendering some stars in a space environment as point light sources.
I use actual celestial coordinates converted to Earth-centered rectangular
coordinates, so my stars end up as a "celestial sphere" surrounding the
Earth. This was working well until I discovered that if I move far
enough in my world, objects that aren't within my "celestial sphere" (such
as the Sun or a distant planet, etc) will appear "behind" the stars. For
various reasons, I don't want to increase the radius of my
"celestial sphere" (in order to physically enclose all my objects).
  If I could somehow "clamp" the depth of the star pixels (in screen
space) to the largest z-buffer value, it would
seem that the stars would always appear "farther"
than any other objects in my world. I read the man pages on
"zbuffer", "zfunction", "zdraw", etc., but didn't find exactly what
I was looking for. So, is there a way to alter the
values used for z-buffer calculations for my stars? (or, for that matter,
any other suggestions on how to solve this dilemma?)

Thanks,

John Vanderburgh
AF Institute of Technology
Wright-Patterson AFB, OH
(jvanderb++at++afit.af.mil)


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