Original post by EmptyVoid
But what I'd really like to know is why you rebuild the index buffer every time you update the chunks
I don't. While conceptually there is one VB/IB per chunk, you will quickly notice that when you're restricting terrain patches to have at most a LOD level difference <= 1, you have 16 possible IB combinations (north/east/south/west = 4 directions, and for each, the adjacent patch is at the same LOD level, or at +1 LOD level, so that's 2^4 combinations). So I precalculate those 16 IBs, and at render time only find which of the 16 combination my patch is in, and use the appropriate IB.