I try to place a prisma in the scene, where the vertex ID 1 is moveable on a surface(plane) and also the vertex IDs 2 & 0 are moveable on the bezier.

enter image description here

I tried the "shrinkwrap"-constraint for the surfacecontact and also the "clamp to"-constraint for the beziercontact, but these constraints unfortunately just work with the origin of the prisma and not with specific vertices.

Is there a possibility to edit these constraints to the specific vertices and not the origin of the prisma?


1 Answer 1


You can use intermediate empties to do that. Here is a UI version (not Python).

For ID1:

Hook ID1 to an empty placed at its location. Then after that shrinkwrap the empty to the plane.

For ID0 and ID2:

Hook them the same way: place 1 empty at the location of the wanted vertex, hook the vertex. But here after that, add a "clamp to" constraint to the empties.

enter image description here

How to hook:

enter image description here

Note: for ID0 and 2, you can also use 1 empty for both if you want to keep a constant distance between them:

  • Select them both
  • Place the cursor at the middle
  • Move the empty to the cursor
  • Do the hook on both

The file here contains this last version:

Following the question in the comments: keeping the shape "rigid", here is another setting.

  • The prism is constrained by a bone
  • The bone follow an empty which is clamped to the curve
  • The bone also tracks to a second empty
  • This second empty: shrinks to the plane, is limited in distance from the first empty and shrinked again to the plane

enter image description here

The new file:

  • $\begingroup$ First of all thanks, this works great so far. But what do I do if i don't want any distortion of the prisma and maintain the original form? $\endgroup$
    – P. Sector
    Commented Apr 6, 2017 at 9:02
  • $\begingroup$ So you want: if ID1 moves the other are moving with no distortion and vice versa for ID0 and 2? $\endgroup$
    – lemon
    Commented Apr 6, 2017 at 9:06
  • $\begingroup$ Kind of, yes. In the end i want to move the whole prisma without distortion with these constraints along the bezier and the plane $\endgroup$
    – P. Sector
    Commented Apr 6, 2017 at 9:14

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