title: rotate a mesh in python to be parallel to a vector
body: <p>I have two meshes (call them A and B) which I am interacting within python using the open3d library (happy to use <code>import trimesh</code> or something else if it works better). Mesh A is a curved structure and mesh B approximates to a flatter surface.</p>
  <p>I need to rotate the meshes so that the surface I am interested in is facing the camera.
  To identify the surfaces that I need I have written functions to turn the meshes into point clouds and create the best fit sphere for mesh A and a best-fit plane for mesh B. These work really well and match the objects nicely.</p>
  <p>I need to rotate the meshes and have gotten stuck with how to perform the rotation.</p>
  <p>The input data that I have:</p>
  <p>for mesh A:
  centroid of mesh A coords and coords of its best fit sphere (+ its radius) - I want to rotate the mesh so that is perpendicular to the vector described by the above data?</p>
  <p>for mesh B:
  centroid of mesh B coords and vector of the normal of the best fit plane - I want to rotate the mesh so that is perpendicular to the vector described by the above data</p>