X-bit labs

eVGA e-GeForce FX 5950 Ultra and PowerColor RADEON 9800 XT: Extreme Overclocking and More! (page 11)

Category: Video

by Tim Tscheblockov

[ 01/04/2004 | 09:43 PM ]

The next demo record is Demo-Mig29-Intercept:

This is a harder demo as it features weather effects like rain and clouds. Instead of a demo flight in a cloudless sky, we have a real air fight here.

The graphics cards show much lower results in this test. We can also note that EVGA e-GeForce FX 5950 Ultra receives a considerable performance boost from overclocking (i.e. it is the graphics card that bears the main workload in this test) and that there is a significant difference between “quality” and “fast” AF modes.

The reason for such performance of the tested graphics cards lies in the demo record itself. Most of the action takes place above the cloud deck, which loads the graphics card.

Let’s see how the gaming engine draws the clouds. When the plane is just a little above the clouds, you can take a peep behind the scenes (take a closer look at the rectangle outlined area):

The screenshot suggests that the cloud deck in Lock-On is modeled in a way similar to the forests of “Il2-Sturmovik”. It is a row of parallel planes that carry textures with “sections” of the clouds. This greatly reduces the rendering speed. First, high-resolution “translucent” textures are used for the sections of the clouds. Second, a number of planes with the sections are at a sharp angle to the line of sight. This makes the adaptive anisotropic filtering algorithms employed in graphics chips from ATI and NVIDIA use highest, resource-consuming, anisotropy levels on part of each of the parallel planes.

As a result, the workload increases dramatically and the graphics cards show much lower results than in the first demo. Note also that EVGA e-GeForce FX 5950 Ultra receives a performance boost when switching from “quality” to “fast” AF, while PowerColor RADEON 9800 XT gets nothing. I suspect this is a well-known “bug” in the ATI’s driver: when “quality” AF is on, tri-linear filtering is only enabled for the first texture. That is, PowerColor RADEON 9800 XT always uses the “fast” variant of anisotropic filtering in this test, without tri-linear filtering.

Anyway, EVGA e-GeForce FX 5950 Ultra looks better than PowerColor RADEON 9800 XT in this test.