Because texture sampling in dgVoodoo2 Glide does not use the GPU sampler (that provides anisotropic filtering) but instead it relies on a custom algorithm in order to be able to fully mimic the 3Dfx sampling process, including TMU-separated mipmap levels and multibase texturing, with only having a performance overhead on the GPU side and completely getting rid of it on the CPU side, making it possible to provide "unlimited" speed (and bug-free implementation) on updating texture memory and texture palettes during rendering that are relatively common in Glide applications.

Unlike Glide, the D3D implementation (all versions use the same backend) is based on the hw sampler, that's why the possibility for forced anisotropy is there.

So anisotropic filtering in dgvoodoo2 would be possible at some cost of speed+some bugs?
I guess you could always turn if off in dgvoodoo2 control panel if the result is not satisfactory.
It doesn't have to be turned on as default 😉

Anisotropic filtering as an algorithm is very complicated so it'd have very large overhead. Even trilinear has (relatively). That's what the sampler circuit is highly optimized for.

So, sorry, but no, I won't implement it. 😐