unexpected results in random rotation validation

[parrenc]

Hi, thank you for providing this amazing library.

I was trying to apply random rotation validation on bcpd_nonrigid.py with the given bunny example, and obtained some weird results.

For example, when applying rotation in X direction by 90 degree counterclockwise. It only took 4 iterations and had an RMSE of 0.3329578008. You could tell from the visualization that it produced a weird shape. (validation result in red dots)

When apply rotation in X direction in X direction by 15 degree counterclockwise. It took 39 iterations and had an RMSE of 0.037521531764196. However, the visualization shows that it produced a 3d stick-like shape. (validation result in red dots)

Here is the link to the results of all of my experiment.
https://docs.google.com/spreadsheets/d/1h7GLeuVPQ0mmztkSOsyosEjR5jvQw7SVpCX44bua_V0/edit?usp=sharing
And here is the link to the validation output PLY files.
https://drive.google.com/drive/folders/1j3NVyijAx_NZHTKLMuxTn9HF1xGPS7ko?usp=sharing

These results do not show a pattern, so I'm wondering what I'm doing wrong here. Are there specific parameters that I need to tune to get the algorithm working? Any help would be appreciated.