[LDCad] Advanced rotation techniques

[N. W. Perry]

I think there are fundamental geometric problems with the "select all three points at once then rotate" approach. This is because you can't specify "the three lowest points" without also specifying an absolute rotation. If you select your three lowest points and then _change_ the orientation of the part, there's no guarantee that the new "three lowest points" are the same three points.

Owen.

Indeed, and another thing is that you won't always have a nice level plane. What if, instead, you need the part to rest against the inside of a box with studs on the bottom? So I think of a step-by-step approach:

1. Move the part downwards until its lowest point hits the highest point of the "receiving" part.
   
2. Locate the point of contact, and rotate around this until the second low point contacts the ground.
   
3. Select the first and second points, get the vector between them, and rotate around this vector to find the third point.
   

This might still be automatable, but it would require analyzing the mesh of both parts and tracking the successive rotations. If a certain point becomes lower than the original lowest point, it has to become the new rotation center.

Still, I think there are certain cases where your eyes will tell you that a plane on one part can be rotated to match a plane on another, and if that's the case it's nice to have a one-step process.