When the full-screen anti-aliasing is enabled, the graphics cards’ performance didn’t suffer too much. I dare conclude that FSAA 4x in IL-2 Sturmovik: Forgotten Battles is no problem for the today’s monsters with 256bit bus and tremendous memory bandwidth. Nevertheless, the situation in higher resolutions changed a little bit in NVIDIA’s favor.
When we enabled anisotropic filtering the picture got completely different. The graphics cards on ATI chips took the lead.
Why so? The reason lies in the peculiarities of the anisotropic filtering algorithms from NVIDIA and ATI, as well as in the gaming engine itself. At first let’s dwell on the gaming engine.
Firstly, to draw the landscape IL-2 Sturmovik: Forgotten Battles seems to be using three texturing layers: two base textures and a “detail” texture reflecting the micro-relief of the surface when you are at the closest distance.
Secondly, a pretty large part of the ground in TheBlackDeath.ntrk demo is covered with woods. The woods are very originally drawn in this game. Instead of drawing each tree separately with the help of sprites or polygonal models, the engine imitates big pieces of woods with the help of five planes located in parallel one above the other at a low level above the ground. The planes are covered with transparent textures with the cross-sections of the trees. Note that these tree cross-sections are located exactly under one another on all five planes. This drawing technique provides excellent visual result at a big angle relative to the horizon even if the distance is not very big. However, as soon as the angle gets less than 30 degrees to the horizon the image turns not so realistic any more. You can even see separate tree cross-cuts.
So, the gaming engine is designed so that landscape drawing requires a lot of texture layers to be applied. Therefore, when anisotropic filtering is enabled it is applied to every texture thus increasing the workload immensely.
And how did our graphics cards perform here? The solutions on ATI chips featuring faster but less efficient implementation of the anisotropic filtering algorithms managed to get far ahead their rivals from NVIDIA.
As soon as FSAA joins the enabled anisotropic filtering the graphics cards performance got somewhat lower, although the overall picture remained the same: ATI based graphics cards were still ahead of NVIDIA based ones although their image quality at “inconvenient” angles was not that impeccable.