Hi Thomas,
For a transformation to be rigid, it should satisfy the following conditions:
1. Similarity Transform: For homogeneous scale, all singular values of the rotation matrix should approximately be equal (within roughly eps of largest singular value)
2. abs(det(T) - 1) ~= 0
The transformation matrix does not satisfy either of the above conditions. Both of these conditions fail due to small differences of about 1e-4.
'rigid3d' is working as expected. For the issue of using the same Transform matrix which worked before, there is a precision issue of what the older exported transformation was and what the new values you are trying to create rigid3d form. There could also possibly a datatype mismatch.
Using the same values as provided in the question, casting the values to single before creating the rigid3d object works fine. Please take a look at the following for single vs double values:
>>href = rigid3d(priorPos)
Error using rigid3d (line 143)
The transformation matrix is not rigid.
A rigid transformation matrix must only contain a rotation and a translation.
The final column must consist of zeros, except for a one in the last row.
Casting into single datatype resolves the issue. But note that doing this might lead in loss of precision.
>> href = rigid3d(single (priorPos))
href =
rigid3d with properties:
Rotation: [3x3 single]
Translation: [0.09997 -0.299979 0.885011]
Hope this helps!
