Hi Ufuk, Joseba,
and also i dont believe culling far plane is a good idea if you are
rendering large area, the increment of performance will not be dramatic.
Actually I've been in a similar position in the past, and my reason to
do it in two passes was so that the very large node (in my case it was a
skydome) would not affect my ability to see objects from very close up.
As you know, OSG automatically computes near/far planes by default based
on your scene, and if the ratio between the computed near and far planes
is too small, it will push the near plane forward. That means that
objects close to the camera will suddenly be clipped. But on the other
hand, I don't want to manually place the near/far planes, or decrease
the near/far ratio too much, because then the depth precision will be
diminished and I will get z-fighting.
So one solution was as Joseba suggested, render the skydome in one
camera and the rest of the scene in another. Another was to use
callbacks to disable near/far plane calculation on the skydome. This
only worked because a skydome is always drawn at the far plane and never
interacts with scene objects. In Joseba's case this would not work
because the terrain interacts with scene objects, so to resolve depth
correctly between the two, both need to use the same depth buffer and range.
Joseba, I don't know why you're getting a black screen, but as I said
above, using two cameras with different projection matrices won't work
for you because then the terrain and the rest of the scene won't have
the same depth range, and you'll get artifacts. What you could do
however, is split your terrain so you can render the far off part first,
with a separate camera and with depth testing and writing disabled, and
then render the close part (that interacts with the other scene objects)
normally. You could even make a system that determines which terrain
tiles are far away automatically each frame so you can move across the
whole terrain without problem. Make sure you disable depth and color
buffer clearing in the second camera.
Another option might be to use a skybox to simulate far off terrain
instead of geometry.
Hope this helps,
J-S
--
______________________________________________________
Jean-Sebastien Guay jean-sebastien.g...@cm-labs.com
http://www.cm-labs.com/
http://whitestar02.webhop.org/
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