Tangent Vector

Hi, this site describes how to calculate the Tangent Basis:

link

Thank you!

And can it be possible to compute it for one vertex?
Because if I computed them per-triangle, how would i pass them to vertex attributes? :-\

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You cannot calculate the tangent basis for just one vertex - as the calculation requires the UV coordinates of the other verts in the triangle.

Sorry, I'm not sure what you mean by "pass them to vertex attributes".

Well, I want to pass the tangent as a parameter for glVertexAttribute.
But as I think, the tangent is same for 3 vertexes.

Hm.. calculating the tangent basis is only the first step to bump mapping. My light still has some error.. It produces very interesting things..

Generally, the tangent vectors of the vertices of a triangle aren't the same. Think about the way per-vertex normals are generated. Each per-vertex normal is the sum and normalization of the normals of the triangles it is a part of. The same is true of tangent vectors, with one difference: you can't generate a per-triangle tangent vector, because a tangent vector can be different for each vertex of a triangle (this is dependent on the texture coords).

I generally use this code (with modifications) to generate my tangents: http://www.terathon.com/code/tangent.php

btw, I don't bother storing the binormal/bitangent; I create it with lBinormal = cross( IN.mNormal, IN.mTangent ) in my vertex programs.