Compute a skinned mesh

I All, I'm loading a collada skeleton. For each bone, I have : - The inverse bind matrix - The local matrix For each vertex, I have : - The position at binding time - The bones and weights to affect A bone world matrix is computed by WorldMatrix = LocalMatrix; if(parent != NULL) AbsoluteMatrix = AbsoluteMatrix * parent->WorldMatrix(); Now, I have to compute all vertex position by the affected bones So I do: vector3 finalposition(0, 0, 0) for each(affectBone in myvertex.GetAffectBones()) { vector3 vertexBoneBindpose = affectBone.InvBindPose().Transform(myvertex.position); vector3 influence = affectBone.WorldMatrix().Transform(vertexBoneBindpose); finalposition += influence * affectBone.Weight(); } But it is not correct, my final geometry is not what I want Is someone can tell me where I'm wrong ? Thanks very much