Solved by ptrblck in post #2 
              
              
                The error thrown in your line of code is because you are trying to calculate the cross product of two 1-dimensional tensors in dim4. 
However, even if you fix it by using torch.cross(m1, m2, 0), you’ll get the following error: 
RuntimeError: dimension 0 does not have size 3

I’m not a mathematician,…