As one of the advantages of Tangent-space normal map (besides few other) is that using Tangent-space NM, normals of animated or deforming mesh can be accurately calculated which cannot be done using Object-space normal map that means for the deforming faces of the mesh, during deformation there might be a situation where normal direction does not change and tangent direction changes, as a result, bitangent/bi-normal will change too.
I am trying to understand in which situations this can happen? (i.e. normal directing not changing but tangent direction is changing)
If above is not the case at all, what makes Tangent-space normal map special for deforming meshes which object-space normal map cannot do.
Copyright Notice：Content Author:「user2259784」，Reproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article：https://stackoverflow.com/questions/51829989/why-tangent-space-normal-map-is-suitable-for-deforming-or-animating-meshes