title: 3 dimensional matrix multiplication in matlab
body: <p>I have a normal map of size <code>m</code>x<code>n</code>x<code>3</code>, where each pixel has a normal vector {Nx, Ny, Nz}.
  I want to rotate each normal vector independently by a rotation matrix. Let <code>R</code> be the rotation matrix of size <code>m</code>x<code>n</code>x<code>3</code>x<code>3</code>, where each pixel has a rotation matrix of size <code>3</code>x<code>3</code>.</p>
  
  <p>I want to multiply rotation matrix at each pixel to the normal vector to get the rotated 
  normal vectors. I am looking for an optimized way to do the task, as looping over each pixel may not be the best way.</p>
  
  <p>Please help!! </p>