Alignment in 3D

Problem Rotate.3dm (3.0 MB)
I have a number of windows that I need to align to the horizon (blue). However the are placed on a curved surface. I need to rotate the blue windows on the red axis so that viewed from the this angle they are aligned with the purple line.

I’ve tried rotate3d but I can’t get the start angle to match the midpoint of the arc. Hope might I do this for a large number of such windows?

Hi Jim,

If I understand you correctly, try this.

1st create a named view and save the current view (you need to do this as the view will change as you will see)
Set the cplane perpendicular to the red curve
Once you’ve done that, rotate the view a bit and then select the named view to reset the camera
Now select the midpoint and rotate the lozenge shape to align with the purple line.

I hope that helps


2DCube Example.3dm (34.4 KB)

Another way:
Set Ortho to on
Make sure that object snaps End , Near and Midpoint are on
Perspective view, Cplane should be World Top or parallel to it
Command Rotate3D
Click end of red line (where the oval object is) first
Click any point on the red line to set the rotation axis
Click the midpoint of the semi-circle
Move your cursor away, Ortho will keep it parallel to the "Horizon"
Be sure NOT to snap on anything, and press Enter
Press escape to stop the Rotate3D command


Problem Rotate.3dm (3.0 MB)

I would like to rotate the BLUE along the RED Axis such that at the end, the blue and purple lines are aligned from the front or back views.

There is a way but it is very tedious if you have a bunch:

In perspective, set a CPlane perp to the end of the red line.
Project the blue line to the CPlane, ProjectToCPlane > Copy=Yes, change its color
Set a Cplane 3Point to the end of the red line and the ends of the blue and projected blue lines.
ProjectToCPlane the purple line and change its color.
In Back, rotate3d along the red line, snapping to the Int of the curve you’re rotating and the projected blue line, then to the Int of the curve you are rotating and the projected purple line…

It IS tricky to get it right because of the way apparent intersection snapping works - you need to make sure the snap goes to the curve being rotated and not the line. I’ll see if I can come up with a better workflow.


I managed to do just that in the way that I described it. And once you have constructed all of the “normals”(the red line), it is not very time consuming to do it multiple times.