Hard Point - 321 PLP alignments are controlled with six points.

Points 1, 2, and 3 form the first "P" in PLP, or the PLANE to snap the measured plane to the nominal plane. This is also the "3" in the "321". It means "3" points are selected to form a plane.

Points 4 and 5 form the LINE (or the "L" in PLP). The line is used like a hand on a clock. The object is spun on the PLANE so that the measured line perfectly aligns with the nominal line when viewing from the top of the plane.

Point 6 is a single point. The measured point is translated in space to the nominal point - taking the model with it. At this point, there will be no deviation, as the points are made to match perfectly. This is why the point is referred to as a “hard point.”

In this model, there is a bracket plane and a hole that is the plane datum.   The hole is drawn as a Space Object circle named "Hole 1" in VTube-LASER.
In the Hard Point - 321 Plane Line Point alignment setup menu below, VTube is told that the three points that form the plane are Hole 1-vertex 1, Hole 1-vertex 2, and Hole 1-vertex 3. (See rows 1 through 3).

In the above setup, circle vertices 1-3 form a plane from the space object circle called "Hole 1."

VTube-LASER calculates the three vertices based on the circle's orientation and diameter.

The following image shows the setup for the LINE part. End 1 is the center of the Space Object circle. End 2 is the calculated midpoint of the master and measured tube.

The following image shows the setup for the LINE part. End 1 is the center of the Space Object circle. End 2 is the calculated midpoint of the master and measured tube.

The hard point is point 6 in this setup. It is the center of the circle.