I have tone mapping working in my app, and I'd like to add multisampling. So that I may perform tone mapping before the MSAA resolve, I'm doing my own custom MSAA resolve by a) binding the multisampled texture and rendering a full-screen quad, b) using texelFetch to grab the individual samples, tone map them, and then blend them.
When I do this, it looks great, but it takes a big wet bite out of my render times (about 3ms). I don't think it's the tone mapping operator, because even if I only grab one sample instead of all 4, the performance seems about the same. This is for a 1920x1080 buffer on my GTX 680.
If 3ms is typical, then I'm okay with it, but since it's a good 20% of my frame time at 60Hz, I want to make sure it's not excessive. Obviously I can't afford to give everything 3ms. I'm using OpenSceneGraph, and so it can be difficult to tell what exactly is going on in terms of the underlying OpenGL, but I'm currently running it through gDEBugger to see what I can find. If you can think of anything I should be looking for, let me know.
Edited by CDProp, 24 January 2014 - 02:35 PM.