Troy Stephen (troys++at++wormald.COM.AU)
Thu, 29 Jun 1995 12:55:33 +1000 (AEST)
A while back I posted a question about the earth-sky model which I was
having problems with and never got a reply. I'll briefly summarize, and
hopefully somebody can give me some ideas:
The problem is related to the location of the sky and ground polygons.
It seems that they are rendered well short of the far clip plane, but
exactly where is impossible to determine - this is a frustrating problem
when you want to specify the exact visual range of your simulation
because simply setting the far clip plane range is not sufficient as your
scene will be clipped by the sky polygon (and NOT the far clip plane as
you would hope).
It also makes it difficult to position celestial objects, because you
never quite know how far away you can project them without having them
disappear behind the sky polygon.
It's real easy to demonstrate - just start up perfly, and with earth-sky
mode set PFES_FAST position a model so that it is just being clipped
by the far clip plane. Now select PFES_SKY_GRND and you will notice
that the model is now clipped closer to the viewpoint.
Would it be possible in Performer 2.0, when the earth-sky
polygons are rendered they are forced to the maximum z-value by:
zMax = getgconfig( GC_ZMAX );
lsetdepth( zMax, zMax );
(or maybe there is a flaw in this proposal?)
Thanks for any ideas.
Troy Stephen
Wormald Technology.
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