hello all,
i did a simple bit of billboarding where i stuffed positions and texcoords for a million billboards into a single VBO (4 vertices per billboard) and hit glDrawArrays (with a simple vertex shader which transforms the position into eye space then offsets it along the texcoord). I got around 200 million triangles per second, so I was reasonably happy with the performance.
But I wanted to save memory…so I gave ARB_instanced_arrays a go - stuffed 4 sets of texcoords into one VBO, then a million positions into another VBO and hit glDrawArraysInstanced.
Now I could maybe understand a slight drop in throughput (well…after all…I’m saving memory and there’s no such thing as a free lunch), but not more than a halving in throughput!
It went from 200mtps to 75mtps. Is this expected behaviour by the IHV’s? If it is, then fair enough I’ll drop it and revert back to not using it - i just want to be clear this is expected performance.
thanks for any advice.
card:Quadro 4000 driver:270.71 os:XP64