Re: Earth-Sky Model Problems
John Rohlf (jrohlf++at++tubes)
Wed, 5 Jul 95 11:56:21 PDT
>
>
> Hi all,
>
>
> 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?)
>
>
This is reasonable but too late for inclusion in 2.0.
However, it is trival to call the above in your pfChannel
draw callback before calling pfClearChan().
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on Mon Aug 10 1998 - 17:51:39 PDT