Geometry nodes: Aligning things
Geonode bread and butter: align this thing to that thing!
Note! Align Euler to Vector is now deprecated, use Align Rotation to Vector instead.
It's generally pretty easy to get a vector that captures the alignment as a direction, but not obvious how to orient something to face that way.
Turns out this is the job of the Align Euler to Vector node. It's not a super intuitive one.
If the axis is Z, and a direction vector is fed to the vector input, you will get a rotation out. For some reason this is typed as vector, not rotation... but when you rotate something by that, its Z axis will become aligned with the vector.
The rotation input can be used to daisy-chain these, so you can align the X axis then the Y axis (and your Z axis is defacto aligned orthogonally to both; you don't need a third node).