I built a terrain component for my engine that loads and renders 8k x 8k square height maps at 60 FPS. The component used a level of detail system to optimize which quadrants could render at higher or lower detail given distance and the index buffers were created to use a H-fractal format when accessing vertices to take maximum advantage of the vertex cache. Stitching between quadrants of different densities is supported and the overall quadrant count across the hight map is configurable. The stitching algorithm itself is a small and fast system that thinks of indices as points in 2D space and creating the next index is treated as a vector translation.