   Tangent space confusion
  Lately I got caught up trying to understand perpicel lighting using normal map..I pretty much grasp the idea but stumble in implementation due to the poor sample not too mention some people use u,v,w and others use b,n,t.One particular method that I was reading needed a tangent T vector in the vertex format (other tangent vectors created after that). the article only include the shader code not the whole code.How do u come up/compute this vector in the first place ? since usually vertex format (from a loaded 3d mesh) only consist of position, normal, texture coordinate.thanks..any explanation or link to articles/sample code will help.. 
  There is an article here on GameDev called Cg Bumpmapping that explains how to calculate T and B (tangent and binormal) using the texture coords and vertex coords of a triangle.Then you can use the matrix defined by T,B,N to transform from texture space to object space. The inverse of the matrix transforms from object to texture space. ;  I asked the same question few days ago. Look at the samples codes and particulary the link to the opengl forumhttp://www.gamedev.net/community/forums/topic.asp?topic_id=227157 ;A good way to calculate the tangent basis. You have to remember that you''re unique, just like everybody else. 