Tips to align Clouds

This chapter lists a few tips to align a cloud with another cloud, or a cloud with surfaces.

These recommendations apply to clouds or to a cloud and surfaces that have similar shapes, where the cloud to align will cover the other cloud or the surfaces.

Do not modify the target (cloud or surfaces).

To reduce the computation time, filter the cloud to align. Use the homogeneous filtering (the repartition of points is more suitable), and choose a filtering value that leaves only a few thousand points.

You can either:

Select the whole cloud to align, and the whole target (cloud or surfaces).

or portions of the cloud and only some surfaces of a model. In this case, be careful that the selected areas/surfaces have similar shapes.

Accept to align inertia axes.

This first step may take a few minutes.

Check whether the cloud has been aligned correctly.
If the result is not correct, undo the alignment and start again. This time, try to select a characteristic portion of the cloud to align, and its counterpart on the target: for instance, if the shape is symmetrical, select a portion that is not. Once again, accept to align inertia axes.

If the result is correct, hide the initial cloud and unfilter the result cloud (use 0 as the filter value).

Select the whole result cloud and the target, and launch the computation, but this time do not accept to align inertia axes. Repeat this step if necessary. If the cloud to align is large, you can filter it, but keep more points than for the first step.

Now, the result seems correct. Use the Distance Analysis for the last controls.
The first set is the aligned cloud, the second set is the target cloud or the surfaces. Set the Discretization at 100, uncheck Min/Max Values, Points and Spikes. Use the Limited color range with the values you require. Faulty areas will appear in red, correct areas in green.
To remove faulty areas, select the areas in red, and some areas in green, and launch another computation. The areas in green will act as a fastener, while the areas in red will be improved.

Altogether, aligning a cloud with another cloud or surface should require 3 or 4 iterations. If the result is not yet satisfactory after 4 iterations, you probably will not be able to improve it.