Occlusion Culling Perfomance Issues/Drop--Comprehensive

[Syx]

Actually, your memory usage dropped by about 15-25 MB. Which seems on par with activating OC. My theory is FFXI poorly uses the IDirect3DQuery9 command for calculating meshes to cull. When you move the camera within the game, it has to recalculate all of the meshes, identify the polygons that can be discarded, and render the scene. That recalculation adds a few milliseconds to the rendering of the scene, at which point the calculations complete and the benefits kick in. So what you're seeing is this backface culling engine at work sacrificing 8-10ms to recalculate all faces of every model's mesh that are not visible on your screen. Yes, this includes characters and objects that were not visible on the screen since the last time the algorithm was used.

The problem is, IDirect3DQuery9 is not a terribly efficient method of culling on its own. Sloppy usage of this query results in lots of draw call overhead and noticeable latency while the GPU waits for the results of the queries. There are algorithms for reusing query data, but there's no way of us knowing if SE uses them without some reverse engineering or a drinking with chatty dev. Anywho, I tested your findings on my system and I see the same drop in GPU (GTX 660 SLI) usage, but I also see a shift in CPU (i5-3570k @4.2GHz) usage. All four cores seem to change their utilization. What I did was slowly pan the camera around the market area in Ul'dah while watching my G15 keyboard's LCD, I saw a 15-30% drop in GPU usage while panning and a 20% spike in CPU usage on one core, with a more moderate 10% increase in the remaining three cores. My fps would dip from 42-45 (22-24ms) down to 36-38 (26-28 ms). Not as drastic as your system, but still a variance of about 2-6 ms in draw time. With culling disabled, my fps remained a constant 36-38 fps during the same panning action as well as stationary. Take into consideration my framebuffer usage is smaller due to running the game at 1080p. Might be time to upgrade your CPU! Hope this information helps.