Transfer rotation attributes from one instance to another

Question

I'm using instances from a collection to generate points on which I will place other objects (instances). I want that these new instances have the same orientation as the original instances.

I tried this but it doesn't work

Any idea on how I could transfer rotation attributes between them?

Thanks

Answer 1

As suggested in my earlier comment, in the absence of a Rotation input node.. (Why isn't there one? Maybe it's coming, unless there's some semantic hitch?)..

..You can instance a single-face proxy on one of the vertices of each of your instancers. That will be created with the instancer's rotation. Its face-index, when realized, should be in sync with the point-index (when the instancers are converted to points).

You can pick up the Normal of the realized proxy, to get the Z-axis of the instancer, and then rotate the proxy by 90 around its local Y to have its Normal point down the instancer's X, and extract that vector, too.

A 2-stage alignment can generate a Euler rotation which can be used as the 'Rotation' with which instances are created:

I've only included a 'Factor' input in the group for debugging and illustration. The group is probably better off without it.

(Blender3.0)

Answer 2

Blender 3.1

With this solution you can create the rotation of the individual objects of a collection with minimal excess geometry:

Here I first move the instances along their local axes on Z and X, and thus create the crucial directions (normals/tangents).

These are then simply turned into a rotation with Align Euler to Vector, and you can use this directly for instantiation or other processing.

_{(Blender 3.1)}

Blender 3.3+

With this version things become a lot easier, because here only the node Instance Rotation is needed:

_{(Blender 3.3+)}