I mean , if I need to apply a hightmap to a terrain with lod above 0 , if I had to step one pixel on the heightmap image to read its value ,then apply the height to the nearest vertex of the terrain ,how could I speed it up such that I skip directly to the next vertex instead of stepping 1 quant in 3d per pixel on the heightmap image ?

I have tried this but the wait(1) inside this loop makes it impossible for realtime , the reason I was trying to accomplish it in real time is because I wanted to generate terrains from coherent noise ,such that I only generate about 3x3 terrains at a time ,while moving through a large scale world ..

but ,I think it's going to be best to pre create the terrains and only load and unload them as I move through the world,because the fastest is to apply the hightmap on a terrain with lod set at 0 , then save it and then load it in the game with lod set above 0.

I thought the wait (1) and lod speed issue was clear from your response so what do you mean "what do I mean" ;-)