8x tri-linear + anisotropic filtering
16x tri-linear + anisotropic filtering
Judging by the screenshots with highlighted MIP-levels, DeltaChrome doesn’t use tri-linear filtering together with anisotropic filtering, despite the settings. However, since there are no typical MIP-banding artifacts on the non-highlighted screenshots, we still can conclude that tri-linear filtering is not missing. All this means that anisotropic filtering algorithms used by S3 Graphics DeltaChrome chip are based on the company’s brand name tri-linear filtering algorithms.
We don’t know the details behind this algorithm yet, but we dare suppose that unlike NVIDIA solutions, DeltaChrome doesn’t use 8 fully-fledged bilinear or tri-linear sample blocks when performing 8x anisotropic filtering, for instance. Instead, the graphics processor selects only two “brandname” 4x4 sample blocks from a single MIP-level. The reference points in these sample blocks are located along the viewing axis projection on the texture. And in these points they perform certain actions imitating tri-linear filtering. In other words, the weight coefficient matrix of the texels taken from 4x4 blocks is the only thing that actually changes during anisotropic filtering. “Large size” of the 4x4 block, if I can say it this way, probably allows using only one block even in case of 4x anisotropic filtering.
As for the texture quality in the DeltaChrome pictures above, there are two things worth mentioning: first, there are no “inconvenient” angles (the anisotropic filtering algorithms by ATI lose their anisotropy level at certain angles), and second, there are no “simplified” tri-linear filtering like by NVIDIA’s solutions. These simplifications just make no sense for DeltaChrome with its tri-linear filtering algorithms. The only drawback we noticed in images provided by DeltaChrome is extremely high level of texture detail (LOD). You can tell this by the distance to the MIP-level borders compared to what we see on the screenshots taken from competitor products, and by the level of “noise” on the textures. Hopefully, in the next driver versions S3 Graphics will reduce the LOD to a common denominator or will allow adjusting it manually.