I am designing a tool that can read an obj file with duplicate meshes in, and export the transformation, scaling and rotation of each duplicate relative to the original model. I can establish the transform from the average of all the vertexes, and I think I can get scale by comparing the maximum and minimum x,y and z values, but I'm completely stumped on rotation. Does anyone have any advice re this?
For identical meshes, this should be relatively easy, as opposed to the harder case of pointclouds with unknown correspondence.
In your case, you can just pick an arbitrary triangle, let's say the first one in the (identical) mesh.
And then find the transformation that transforms triangle T0 into triangle T1.
Additionally, there is also a method for mapping point clouds that are noisy, yet have known correspondence.