Best Fit Registration

This command analyses the overlap of selected objects to calculate the best fit of these objects. Best fit means the transformation that minimizes the distance with other objects in a least squares sense. This function assumes that the first object in the selection is the reference immobile object, unless you want to replay the previous best fit operation. Insure that all objects are roughly pre-positioned or fit the conditions where the automatic pre-alignment will work. To obtain a good result, it is highly recommended that the immobile object covers the main part of your model.

1. Focus to the fixed object by clicking Show and go back to the previous display with Restore. Using Set allows to select another fixed object in the current selection, or to select a new one.

2. Select the type of best fit you want to calculate:

   • All together means that if N objects are selected, the best fit of each object is computed with the other N-1 objects.

   • On fixed object means that objects 2 to N are all best fitted with the fixed object.

   • Compensate ball radius on fixed surface or mesh means that you will have to enter the probe radius value of the probe that was used to make the point clouds. Measured points are objects 2 to N and assumed as sphere centers while the fixed object is considered as the reference model with the true dimensions (mesh or CAD surfaces). When you enter the sphere radius, red balls are displayed on the surface of the reference object. You may swap the option Other side compensation to have the spheres on the same side as measurement ball.

3. The Enable scaling option is available when the registration is made on the fixed object of the selection. This allows comparison of a part and its pattern when the part has been modified due to thermal modification.

4. If your selection contains at least two surfaces or meshes (or clouds containing scanning direction allowing to determine the local orientation side to be best-fitted onto a surface), you will have the possibility to select the type of attraction that should be done between two overlapping areas. If you select Make attraction between all sides, an attraction will always occur between overlapping areas, whatever the normal orientation is. However, if you select No attraction between surface sides with different orientations, the best fit will only occur in the case of picture 1 and not in the case of picture 2.
   
   A default threshold is defined by the software. However, you have the possibility to adjust this value if necessary by checking User-defined threshold. This threshold defines how far a point is considered as overlapping the one on the other object.

5. If the conditions are fulfilled, you can apply an automatic pre-alignment by checking Pre-align in a first step.

6. You can add some constraints to the Best-Fit:

   • Rotations. You can:

     • Allow all the rotations: by default alignment behavior, no constraints will be applied.

     • Preserve the orientation of the X axis: the rotation will be only around the X axis, no rotation around Y and Z.

     • Preserve the orientation of the Y axis: the rotation will be only around the Y axis, no rotation around X and Z.

     • Preserve the orientation of the Z axis: the rotation will be only around the Z axis, no rotation around X and Y. If Z is the correct vertical in all your objects, as it will not move during the best-fit, the vertical will still be correct at the end of the best-fit.

     • Disable all rotations: the alignment will be only a translation.

   • Translations. You can disable each translation (along X, Y or Z) by unchecking the corresponding option.

   • If at least one translation is disabled, you will have to define the rotation center (by default it's the center of the bounding box for each object). Click on the purple circle to be able to click a point in the 3D scene. You can also modify the X,Y,Z fields manually.

7. Click Preview to see if the result fits your need.