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I have 4 arms one of them being the original collection the other 3 collection instances (picture 1). The original is parented to an empty and follows that empty like it should, the instances however don't they move away from the original point (picture 2). Is there a way to make them stay in their relative position around the empty when the empty is moved or is there a better way of "instancing" the arms to get a better result?

Image 1

Image 2

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  • $\begingroup$ Hello and welcome. Please use a title that matches the content of the post. It should read like a question, be descriptive but succinct, unique and identifying, summarizing the problem so anyone searching for similar issues is likely to find this. Remove anything superfluous, avoid vague words like "this", "help with", "issue", "like in image" "question about", instead describe what "it" is. Your title is the first thing visitors see, answers you get depend heavily on it. See What is the problem of asking “How do I do this?" $\endgroup$ Commented Oct 16 at 12:06
  • $\begingroup$ if you move the original object away from the world center, il will move the collection instances away as well, do you really need the original object? Can't you create a third collection instance instead and mask the original object? $\endgroup$ Commented Oct 16 at 12:22
  • $\begingroup$ @moonboots Yes I suppose I could, how do I then connect the instances to the empty in the best way? $\endgroup$ Commented Oct 16 at 12:47
  • $\begingroup$ you should describe your whole project a bit more, maybe collection instances is not the best solution? $\endgroup$ Commented Oct 16 at 12:57
  • $\begingroup$ Thees four arms basically act like a claw and are rigged to open up. The claw is connected to another arm that rotates up and down. I basically want to move the entire "claw" when the arm that connects to the claw moves. $\endgroup$ Commented Oct 16 at 13:19

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When a collection is instanced, its representation in world coordinates becomes the representation in the instances' local coordinates. If you transform the collection, either directly or indirectly by parenting it to an empty or other object, it will move in world coordinates, and the instances will reflect this transformation in their local coordinates. If the instances are rotated with respect to each other, movement (direct or indirect) of the original in one direction will translate to movement in various rotated directions for the instances.

This is rarely what you want, so it's better practice to keep the original around as a "master copy", fixed at the world origin and oriented in some way that makes sense for the object and made invisible in renders and/or the viewport. Then, instance all the copies you want to actually be visible in your scene.

So, if you have a "claw" modeled in world coordinates at the world origin placed in a collection:

enter image description here enter image description here

You can exclude the whole collection from the view layer in the outliner, so it doesn't appear in renders and in the viewport:

enter image description here

and then create four instances. The instance origins (i.e., the position of the empty automatically created for each instance) will correspond with the world origin of the original. Here, I've rotated them around the Z axis to place them in position, without moving the original collection:

enter image description here

Now, if they're all parented to something (an empty, or in this case a cube), they'll all move as a unit, since the original collection isn't being transformed:

enter image description here

Note that you can take advantage of the common transformation power of the original, if you want. For example, if you rotate the original (invisible) Claw collection around the y-axis, the whole claw opens and closes with a single movement. Technically, you could make this (part of) your open/close rigging.

enter image description here

This may be more trouble than its worth, though, since there are more direct ways to rig a common movement of multiple bones using armatures.

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