Aligning Clouds

task target 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 reference cloud or the reference surfaces.
  • Do not modify the reference (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 reference (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.

This first step may take a few minutes.

  1. Check whether the cloud has been aligned correctly.

  2. Depending on what you see:

    • 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 reference:
        for instance, if the shape is symmetrical, select a portion that is not.

    • If the result is correct,

      • Hide the cloud to align and unfilter the output cloud.

      • Select the whole output cloud and the reference,

      • 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.

  3. Now, the result seems correct:

    • Use the Deviation Analysis for the last controls.
      • The first set is the cloud to align, the second set is the reference 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.
  4. 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.

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