“Application”, “Balanced” and “Aggressive” Modes

We have already mentioned earlier in this review that the driver offers three work modes for NVIDIA GeForce FX 5800 Ultra, differing in performance-to-quality ratio: “Application”, “Balanced”, “Aggressive”.

Let’s make GeForce FX draw a picture in different modes. For the beginning, we took a small test program drawing a pyramid with the base “lying” on the screen and a far-off vertex. The pyramid has many sides and looks like a cone. A “tessellated” texture is laid over the sides of the pyramid; MIP-levels are “highlighted”; tri-linear filtering is on:

Now, a fragment of this scene as rendered by GeForce FX in different modes:

Application

Balanced

Aggressive

Take a look at the color transitions between MIP-levels. In the “Application” mode they become “blurred” thanks to tri-linear filtering: at this kind of filtering, a pixel color is created as a combination of two values taken from two neighboring MIP-levels and summed up with weights depending on the distance to the pixel. That is, tri-linear filtering should result in smooth and continuous half-tone transitions in this test scene.

But we only see this smoothness in the “Application” mode. In “Balanced” and “Aggressive” modes, the smooth transitions get broken into pieces: some of the pieces have tone transitions and some are colored in pure tones.

This can mean only one thing: GeForce FX uses a combination of bi-linear and tri-linear filtering in “Balanced” and “Aggressive” modes instead of true tri-linear filtering. You can see it with a naked eye that tri-linear filtering is performed on less than a half of the image area in the “Balanced” mode, and on less than a quarter – in the “Aggressive” mode.

Now, let’s add anisotropic filtering of the maximum 8x level to the enabled tri-linear filtering:

Application

Balanced

Aggressive

It’s perfectly seen that besides the mixture of bi- and tri-linear filtering, the GPU shifted MIP-levels closer to the observer in “Balanced” and “Aggressive” modes. In other words, it lowered textures level of detail (LOD).

Let’s take a real gaming scene from Serious Sam: The Second Encounter. The game ran in OpenGL, with 32-bit color depth and “Quality” graphics quality settings. We used the “GFX: Extreme Quality” add-on. To make the transitions between MIP-levels visible, we enabled their “coloring” and used only bi-linear filtering:

Here is a fragment of the screenshot taken in different modes:

By the evident shift of MIP-levels we conclude that the modes use different textures level of detail.

But this is not all, yet. Other fragments of the same scene…:

…indicate that GeForce FX uses forced texture compression in the “Aggressive” mode. You can see the artifacts of this compression in the sky texture and the heart icon. Texture compression is most annoying when used on “transparent” textures. For example, here is a screenshot of the same scene taken in “Application” (left) and “Aggressive” (right) modes:

So, forced texture compression and reduced level of detail are well-known methods of reducing the amount of texture data requested by the GPU. This lowers graphics memory bus workload and increases performance at the expense of worse image quality.

But what does GeForce FX get by substituting “true” tri-linear filtering with its “quasi” variant in “Balanced” and “Aggressive” modes? Only the reduction of requested texturing data? Or is this somehow connected with the new “fast” anisotropic filtering from NVIDIA? Let’s figure it out.