[Algorithms] texture space

[Vladimir K. <vka...@si...>]

Hi All,

I know similar question was discussed here some time ago.
But I need a bit more info.

I want to put dot3 bumpmapping onto animated character.
To transform light vector into texture space I need to calculate
orthonormal basis for the tangent space for vertex.

How can I calculate tangent vector of this basis ?
How it depends on texture coordinates of face ?

I found not bad example for this at nvidia site - md2shader.
But I don't understand how it's done here.
In md2shader used only one tex coordinate for calculations.
I think it's wrong.

I know you say that it's school level question.
But may be somebody can point me good code example 
or explanation.

Thanks
vlad