Constraining fine registration to a particular axis

[BenEvans]

I am trying to use fine registration to match two clouds with quite different resolutions and slightly different extents. I effectively have a plane in Y and Z dimensions and am interested in change in the X dimension. I have been trying to register my higher-resolution clouds (SFM) to lower resolution (Laser) clouds prior to using the M3C2 plugin to calculate differences between the high res clouds. I am happy that the registration in the Y and Z dimensions is good enough, given how planar the features are, but the X is another matter.
I have tried using the fine registration tool and unchecking the Ty and Tz translation boxes, but when I do that no transformation is applied at all.
When I register with everything enabled the aligned cloud is shifted significantly in the Y direction as a result of differences in extent and changes in the point density of the lower res cloud along that axis.

Am I missing something? I just want to leave the Y and Z positions as they are and minimise the differences by shifting the aligned cloud in the X only. Any suggestions on how to achieve this?

Many thanks

Ben

[daniel]

It would be easier for me to understand with a screen capture, but in general, you should always use the highest density cloud as 'reference' (it's always possible to reload the original data, and apply the inverse transformation to shift the clouds the other way if that matters).

Then if the extents of the cloud is different, you have to change the 'overlap' parameter accordingly.

And last, I'm not sure about why disabling the Ty and Tz translation components has no effect in your case (I would need to see the data) but this feature is 'research' only and it's also possible that the clouds are 'locked' in their current position and cannot 'unlock' if you prevent the algorithm to move the clouds along Y and Z.