Frederic BOUVIER wrote:

> I wrote:
>
> > We can also begin to think about a multi pass method that would :
> > 1. draw the clouds above the viewer without depth update,
> > 2. draw the scene,
> > 3 .redraw the clouds above with depth test
>
> Thinking more about it, for the record if someone wants to toy with this :
> 0. clear the stencil buffer
> 1. draw the clouds above the viewer without depth update,
> 2. draw the scene with stencil buffer write enabled ( terrain and objects
>    overwrite all clouds, even those that are between the viewer and the
terrain )
> 3 .redraw the clouds above with depth test and stencil test to only
>    update terrain that can be obscured by clouds - this should clear the
transparency
>   'drawn twice' problem
>
> > With an impact on framerate due to double writing and problem like
> > the one Melchior is experiencing with overlapping semi transparent
> > objects. Haven't thought about it much of that.
>
> Obviously, this should be optional to accomodate less capable hardware

I manage to implement this algorithm tonight. The results are here :

1. /sim/rendering/multi-pass-clouds=false :
 http://perso.wanadoo.fr/frbouvi/flightsim/fg-multip-off-1.jpg (204kb)

2. /sim/rendering/multi-pass-clouds=true :
 http://perso.wanadoo.fr/frbouvi/flightsim/fg-multip-on-1.jpg (198kb)

3 /sim/rendering/multi-pass-clouds=true ( billboard tree detail ) :
 http://perso.wanadoo.fr/frbouvi/flightsim/fg-multip-on-2.jpg (106kb)

If you think it's worth being in the release ( being optional
thanks to property ), just speak and I will prepare a patch
tomorrow evening ( sky.[ch]xx was touched in SimGear, main.cxx
in flightgear, preferences.xml in fgfsbase )

Otherwise, I'll hold off until the release is out.

Cheers,
-Fred



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