Okay, so I've been trying to find the cause of a reported slowdown with something I work on. I'm a hobby programmer and I work on a faster, better engine for a Half-Life mod, and I mostly do my programming on WON Half-Life, which is the ancient retail version of the engine. I do this because unlike the Steam version, it allows me to debug the code. Here performance is usually good, unless I enter a heavy are, but even there, the lowest I get is 37 fps with 3 renderpasses.
However, there is the Steam version of Half-Life, and it runs ungodly slow. After a long session of profiling and cutting off bits of the code, I've come to the conclusion that it's rendering from VBOs that's slow. I store all of my rendered geometry in a single large VBO as simple triangles: the world, the models, and particles. Now I run everything through ARB shaders, but toggling these brings absolutely no difference in performance.
But when I render on Steam HL without vbos, just immediate mode, performance is at the absolute top, whereas rendering the same geometry as VBOs brings it down to like 40 fps, and it's not even that much. In one scene where in the WON version I get 75+ fps, in the Steam version I get 28 fps at best.
So yeah, I'm digging around, trying to find the cause, but I figured I might as well ask for some help on the matter, but I figured I'd ask: what on earth could possibly cause such a grave performance difference between the two platforms? At the momment I'm totally clueless. What could this platform be doing that is completely ruining VBO performance?
I've found the problem, after a very long session of digging through code with gEDebugger, I figured that maybe Steam HL, unlike WON HL, somehow used vertex arrays, and I used vertex attribs. I've eventually found my guess to be true, and a client state being enabled was causing the crippled performance. You can disregard this.
Last edited by MagnumOpus; 06-02-2013 at 04:22 AM.