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Seen a lot of examples, geometry nodes and prior, older versions of Blender, but, not this. I might've missed it.

Since some things have changed between 3.0x and 3.1. Basically an array of cylinders, for example. In a circle they go straight up, evenly spaced. That parts not too hard to do and numerous examples. What I'm looking to do and not finding a straightforward or simple example, maybe I can have one, but not both, ok. I'll go for straightforward. What I want is to:

  1. Rotate like dominos that face each other in a circle, tip any one and they all fall down 1b) Rotate them 360 degrees around origin center - like spinning in place
  2. Rotate them 360 degrees inward so they all face the center - lengthwise 2b) Rotate them 360 degrees outward so they all face away from the center - lengthwise

Probably most easily shown with a Suzanne. One is inward or outward like a top. The other is like rotating forward and back lengthwise on a massage table from right side up to upside down either looking down at the floor or up at the ceiling (or some point in between) - if that makes sense.

Ideally easily modifiable. Maybe even Geometry Nodes Menu options for each. In 3.0 and 3.1 that's become more possible all connecting back to and from Group Input.

Whether Cylinder, Suzanne, or Cube, they should all behave the same way.

Radians, Degrees, Tangents, no clue, but, I'm guessing somehow they figure into this.

I've seen several very complex, poorly explained array examples that I haven't been able to figure out. Anyone got a solution that does?

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1 Answer 1

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I'm not sure I totally understand, but maybe something like this?

screenshot showing instance rotation nodes

The input geometry is the Suzanne.

  1. Instance the suzanne onto the points of a mesh circle
  2. The first Rotate Instances node makes the suzannes point to the centre
  3. The second RI rotates each suzanne around its own origin - taking the 3 rotations from the 3 Modifier inputs. I think this gives you the rotations you want?
  4. The third RI rotates the ring of suzannes around the main origin - like a merry-go-round. Is this your item 1b?

You can use the drop-down to re-use the same node set-up on a different object:

screenshot highlighting node selector dropdown

It seems like you have to have added a GN to the new object before you can use the dropdown. Maybe that adds the modifier, and then the dropdown allows you to choose the node group.

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  • $\begingroup$ It's near perfect. The only thing missing would be the ability to choose "Object Info" perhaps a different object as desired rather than having to recreate the nodes specific to the object. Other than that, even if only that it's exactly what I was looking for. Consider it solved. Anyone interested - pasteall.org/blend/522c1f6e7c034f9b8ffd878c69b53550 $\endgroup$
    – unkerjay
    Mar 17, 2022 at 17:57
  • $\begingroup$ @unkerjay, I've added a bit on re-using the same node group on a different object. It might be possible with an Object Info as well. $\endgroup$
    – David Wood
    Mar 18, 2022 at 9:21
  • $\begingroup$ @unkerjay, BTW I see that this set-up only works if the objects' origin is at the world origin. You'd have to rebase the rotations if you'd Applied a translation to the base object. $\endgroup$
    – David Wood
    Mar 18, 2022 at 9:22
  • $\begingroup$ I didn't test this, but isn't this what the "Local Space" checkbox is for ? $\endgroup$
    – Gorgious
    Mar 18, 2022 at 9:37
  • $\begingroup$ @Gorgious I don't think my previous comment makes any sense, now I have had a look. When you Apply a transformation, it moves the object's origin back to the world origin, so naturally that will affect how the object is placed as an instance, and how it rotates. The "Local Space" checkbox lets you rotate the objects around their own origin (in the first two Rotate Instances - to make them face the middle of the circle and to pitch/roll/yaw). It's switched off in the third, 'merry-go-round' Rotate so they all rotate together around the center of the circle. $\endgroup$
    – David Wood
    Mar 18, 2022 at 14:54

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