Orientation

This constraint forces two normals to have the same orientation.

A normal has a direction; it is drawn as an arrow in that direction. The direction of that arrow could be specified by two angles. The normal specifies those two angles, plus one additional angle that corresponds to the twist about that arrow.

Note

Technically, a normal represents a rotation matrix from one coordinate system to another. It is represented internally as a unit quaternion.

For example, the picture below shows two workplanes, whose normals are constrained to be parallel:

..image:: images/ref-parallel-normals.png

Because the normals are parallel, the planes are parallel. But one plane is twisted with respect to the other, so the planes are not identical. The line on the left is constrained to be horizontal in the leftmost plane, and the line on the right is constrained to be horizontal in the rightmost. These lines are not parallel, even though the normals of the workplanes are parallel.

If we replace the parallel constraint with a same orientation constraint, then the two workplanes become identical, and the two horizontal lines become parallel.

This is a useful constraint when building an assemblies; a single “same orientation” constraint will fix all three of the imported part’s rotational degrees of freedom.