Hmm yes that makes sense. What i'm doing so far is using VTF in the PS (not VS) to obtain normals. I think i might move this to VS or simply send in normals with vertex lke you said. Then i use an alphamap with 3 values (2 texture IDs and 1 weight) for the splatting, as apposed to the usual 4 splat weights channel. This gives me more textures to work with but limits me to 2 textures per vertex, which isn't a problem really. I also use detail maps.

Anyway, for the tangents and bitangents, is it better to send them in with the vertex or generate on the GPU? By better i mean performance wise.

@Scouting Ninja, thanks for the visual aid :)

Alright thanks i'll keep that in mind.

Extracting a normal (and by extension the whole TBN frame) is still not as straightforward as one might think.

You can cheat your way out of needing a TBN frame if you perform your lighting in object space.

In object space, your terrain is always a regular grid, and the (approximate) tangents and bitangents lie along the grid axes.