Wjbender you currently go from heightmap data and try to convert that into mesh data, right? Why not just take a vertex position and calculate the corresponding pixel position, like px = (int)(clamp((vertex.x-min_terrain_x)/size_terrain_x,0,1)*(bitmap_size_x-1); then read the height at the position via pixel instructions?
"Falls das Resultat nicht einfach nur dermassen gut aussieht, sollten Sie nochmal von vorn anfangen..." - Manual
