I’m doing work on older GPUS which only support 16bit indexes for DrawIndexedPrimitive calls (and I assume the same for OpenGL as a hardware limitation).
While I understand this means obviously all indices have to be under 0xffff and therefore at most 65k vertices, I can’t find a good answer to what limit this means for the maximum number of polys you can draw at once. Does it mean the index buffer is also limited to 65k elements – about 22k triangles – or could you send 100k triangles at once if you wanted to, from your 65k indices?
The size of the indices you happen to use in a draw call is not related to the size of the index.