More terrain questions

#1 Here's a start for ya:

http://www.gamedev.net/reference/programming/features/quadtrees/

Hope it helps.

#2 The algorithm would take a few pages to describe :) If you want an idea of how LOD on terrain works, you should search the resource database for Terrain LOD. There are number of rendering articles and reading a few of these should give you an idea of what's involved. At some point we'll have to get Mark Frohnmayer to write something up on this one (he wrote it). I could describe the one I wrote for Tribes 1, but I like this new one better :0

#3 Just a basic overview of your question:

Lets say you have a human face that has...300 polys, when you are up close, all 300 of those polys would matter...however at, say 20 feet away, they don't. But you still need to see things like a nose, insets for the eyes and such. What a LOD algorithm would do is do things like maybe flatten out a cheek by removing a vertex and merging the 4 triangles that made up the little cheek-bone protrusion and making them into...say, 2. (This is just an example) You loose detail in poly count, but it's not very noticable. It's not as easy as it sounds, but that's the basic idea.

#4 Thanks, guys. About the last reply, what I was asking is how the jumps from one LOD to another are made without popping or warping, like in Tribes 1.

#5 Hmmm, well in just looking at the problem my quick solution would be to mark some terrain vertices as static, and I'd make sure to do a trace of the tops of ridglines by grabbing the highest 3% of the map and marking it static, that way mountians wouldn't 'grow' like they did in Tribes 1.

#6 Thats what I had thought at first, but then I noticed warping on all areas of a hillside in Tribes 1. Maybe it does warp, but it reaches the highest detail level at a distance where it is unnoticeable. I have no idea...

#7 Changing LOD without popping is often accomplished with "geomorphing", which is basically where vertices are merged over time - ie, two verts will gravitate toward each other over the course of a few frames, then merge.

#8 I'm pretty sure thats what T1 used. Thats what causes the morphing. I was just wondering how LOD transitions are accomplished (if at all...) withought popping or geomorphing or something else that causes warping.

alas, an answer may never be... figured out. At least by someone not verrrry familiar with the techniques used here.

#9 Well, I certainly can't see any way to do it. I've only seen three ways to do terrain LOD - standard mesh decimation, decimation with geomorphing, and mesh mipmaps.

None of them are perfectly seamless, but if geomorphing is actually done well, it isn't very noticable - and all but unnoticable at higher detail settings.