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HamsterofDeath
12-27-2002, 03:47 AM
i'm programming an outdoor-engine...
the most difficult part ist probably to draw only the visible part...
for now, i am here :
- build an octree
- calculate which end-of-octree-boxes are visible because of their distance to the viewer
- reduce the number of visible parts down to 1/4 by frustum culling

quite good, but not enough.
lets assume i stand in front of a hill. all i see is the hill, containing 200 triangles. behind it is another hill, a bit smaller. behind this one is another and so on.
i see 200 triangles, and MUCH more are calculated.

my idea is : you can see 1,2 or 3 sides of an end-of-octree-box. is it possible to ask opengl "has anything been drawn there yet ?"
if yes, i could skip the box, and all polys contained in it, by "theoretically draw" 3 quads

Joel
12-27-2002, 04:13 AM
Originally posted by HamsterofDeath:

my idea is : you can see 1,2 or 3 sides of an end-of-octree-box. is it possible to ask opengl "has anything been drawn there yet ?"
if yes, i could skip the box, and all polys contained in it, by "theoretically draw" 3 quads
see here : http://www.opengl.org/discussion_boards/ubb/Forum3/HTML/008313.html
especially the last post of pbrown that gives details on how to use this extension

And it has been discussed in other threads to...

HamsterofDeath
12-30-2002, 08:14 AM
looks like this only works with nvidia-cards...
i don't want to use anything chip-specific ...

zen
12-30-2002, 08:33 AM
I came across some papers/tuts on terrain occlusion culling (in SW of course).I don't have any links but you shouldn't have much trouble with google.I doubt they're worth the implementation though.

HamsterofDeath
12-30-2002, 10:00 AM
i got another idea :
i pick out a high point (for example the highest point of every hill) then find out the biggest cone possible that fits under this point without touching the landscape -
from a single point of view, the cone is a triangle, and every octree-box completely behind this triangle is invisible
few calculations - big speedup

Julien Cayzac
12-30-2002, 12:16 PM
Originally posted by HamsterofDeath:
looks like this only works with nvidia-cards...
i don't want to use anything chip-specific ...

ATI supports that extension too.
Since it's a so-called "directx9 feature", I guess it will eventualy become an ARB extension next year...

Julien.