CloudCompare forum

I would like to compare cloud to cloud but first I need to match both clouds together. How does self-matching work? When using the "finely registered already aligned entities" function, when I select all the matching points, will the cloud not be deformed, stretched so that the program fits them? When fitting two clouds together, won't it distort the cloud-to-cloud comparison?
Or maybe it's better to manually match "Aligns to clouds by picking equivalent point pairs"?

Is there a plugin that shows with vectors in which direction the clouds are tilted relative to each other?

No, ICP is a rigid registration algorithm. All points are taken into account, but that's just to minimize the errors (not to 'stretch' the cloud).

Still, it is a good idea to set the 'overlap' parameters correctly, in order to avoid taking into account points that are far from the 'reference' cloud.

See https://www.cloudcompare.org/doc/wiki/index.php/ICP

Is there a plugin that shows with vectors in which direction the clouds are tilted relative to each other?

Not sure to understand, but ... probably not ;)