A well known feature of a GPU is the post transform vertex cache, used in cases where a drawcall uses an index buffer to index the vertex to be processed, to cache the output of the vertex shader for each vertex. If subsequently the same vertex is indexed, as part of another triangle, the results are already in the cache and the GPU needs not process that particular vertex again. Since all caches are of limited capacity, rendering engines typically rearrange the vertex indices in meshes to encourage more locality in vertex reuse and better cache hit ratio.