Re: [Algorithms] Terrain Organization

[Tom H. <to...@3d...>]

At 01:03 PM 7/30/2000 +0200, you wrote:
>Check the archives on this one, but I think someone (nVidia, perhaps?) said
>once that on TnL type cards it is more efficient to pump the polygons at the
>card than to spend too much time (ROAM) LODding on the CPU. If that is true
>(I for one think it makes sense), the recursive quadtree you described would
>work just fine. Apparently, terrain LOD has no future with TnL - unless you
>want some extremely detailed stuff up front. Anyway, if your terrain has 5-10
>K polys in an average scene, you could care less if you LOD it down to 2-5K
>on a TnL card...

I have a few problems with those assertions:

1. A terrain with 5-10k polys in the scene is pretty weak. To have good 
detail up close, and have a large view distance (10,000 meters is a goal 
for me, although infinite yon clip with a spherical world would be even 
better) you end up with 100s of thousands of triangles in a single scene at 
full tessellation.
2. Not everyone has TnL capable machines, and it is generally a "good 
thing" if your engine can scale across systems with different geometry 
performance.
3. You _can_ do continuous terrain LOD on a TnL card, but you are bound by 
the LOD calculation itself, and hence, CPU speed as you mention. However, 
things can and are being sped up greatly on this front, both with faster 
CPUs, and better split metrics.

Now, that isn't to say that CLOD terrain is for everyone. Far from it. For 
small view areas and rather coarse tessellation of static terrain, just 
drawing a static LOD works quite well.

Tom