how calculate tangent and binormal for tangent space ?

I didn’t found something about it. Can you explain me or give me a link ?

I 'm working with triangles and i have already computed the per vertex normals

Look at nVidia and ATI developer pages (follow the Developers link from both sites). They contain papers (most of them is on nVidia page) about this subject. At ATI page there is also reasonably commented source code of tool that can generate tanget space normal maps. During generation it calculates the tangent space so you can look in it to see how it does that.

There is a rather over-long explanation of how to do this, along with code, on my website at: