Shawn Chang said:In actual drawing, the index buffer only uses three vertices 0, 5, and 7. But the GPU side will also execute the calculation of the five vertices 1, 2, 3, 4, and 6?
Yes. Don't leave unused indices in the active index range, aim to reference every vertex between min and max.
For implementing mesh level-of-detail, duplicate vertices and have a compacted index range for each LOD, don't make low resolution meshes by sparsely sample from the LOD 0 mesh.