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I'm very new at this, and have found how to constrain an empty's transforms to an object...but I'm unable to constrain an empty's transforms to a specific vertex of an object (I'm using solidified icospheres and the vertex is essentially the "north pole"...but I plan on having several special locations).

It seems that if I place the empty on the correct vertex, select the empty, and then create a transform constraint I can only pick the sphere as a whole for what I constrain to...not a vertex on the sphere's surface. It won't let me go into edit mode in the middle of picking what I am constraining to, and the vertex itself is not individually available for selection.

When my sphere rotates or translates I want several empties to stay on the surface of various special points on my icosphere, and the plane of the original point of mounting the empty should remain parallel to the tangent of the sphere surface (I'm placing empties with xy plane tangent to the sphere surface).

Perhaps this is better done with parenting (though I'd still need constraints for location, scaling, and rotation) plus constraints? Think of it as marking the location of cities on a globe and knowing which way is up or north.

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You can use "make vertex parent" to do that:

enter image description here

It is some kind of the invert of the hook:

  • Place the empty as wanted
  • Select it
  • Shift select the sphere
  • Enter edit mode for the sphere (maintaining the empty selected)
  • Select the wanted vertex of the sphere + 2 other vertices: because 3 vertices are needed to define an orientation plane
  • The make them parent of the empty using CtrlP

enter image description here

The result is visible here:

enter image description here

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  • $\begingroup$ Thank you, that worked! I had been stuck in part by trying to select a non-existent vertex in object mode...I hadn't realized I could select both and then go into edit mode. One question though...will I be guaranteed that the empty will remain tangent to the sphere surface rather than the face of the individual triangle (the picked points are non-colinear points which are close to tangent, but not actually tangent). $\endgroup$ – D. Stimits Apr 2 '18 at 17:55

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