Hello Teem users,

I have a question about the usage of tenInterpDistanceTwo_d function.
I want to calculate the orientation distance between two tensors.
Tensor A = [4, 0, 0, 4, 0, 4] i.e., perfect sphere.
Tensor B = [10, 0, 0, 1, 0, 1] i.e., linear shape tensor.

My expectation is that if a tensor is compared with a sphere tensor, the orientation should be 0. 

tenInterpDistanceTwo_d can give me a value very close to 0.

But if I change B to [1, 0, 0, 10, 0, 1] or [1, 0, 0, 1, 0, 10], the function returns a very large orientation distance value. But B is still a linear shaped tensor. This is not what I expect.

What is the reason behind this?

Furthermore, in the paper Geodesic-Loxodromes for Diffusion Tensor Interpolation and Difference Measurement, page 6, it says ''there is little orientation change between isotropic and anisotropic
tensors of comparable size".

In this case, B is very anisotropic tensor and A is a perfect isotropic tensor and both have exactly the same trace (=12, i.e., the size in the context), why it returns a large value far from 0.

Thank you very much.


Changgong Zhang
Ph.D candidate in Computer Graphics and Visualization section
TU Delft