From: John Harries <jharries@io...>  20020228 14:01:41

Yes, you need to retransform. Your tangent space is defined by the vectors S, T and SxT. (Where SxT is cross_product(S, T)). Note that SxT is also the vertex normal. S and T should be derived from the texture coordinate derivatives only once. Since S, T, SxT forms an orthonormal basis you can transform S and your normal and then perform a crossproduct to calculate T. Easy in a vertex shader. Does this help? John Original Message From: gdalgorithmslistadmin@... [mailto:gdalgorithmslistadmin@...]On Behalf Of Adam Moravanszky Sent: Thursday, February 28, 2002 7:33 AM To: Algorithms List Subject: [Algorithms] Skinning + Tangent vectors Hello. I am completely new to mesh deformation with bones, so this may sound naive: If I have a mesh which needs tangent vectors per vertex (for bump mapping, for example) , should these be animated along with the vertex positions and the normals, or can that be avoided? Regenerating them from scratch every frame from the unchanging texture coordinates is too expensive??! P.S: I am doing skinning in software with Cal3D so this need not be hardware friendly. What I would like to avoid is rewriting my shaders to light in any other space than standard tangent space. P.P.S: I saw in the archives that this is supposedly covered in the book "Mathematics for 3D Game Programming & Computer Graphics", but alas, I don't have it. Thanks, Adam 