How to Make a Joint Follow the Rotation of a Spline
In Cinema 4D, you can use Constraints to make a Joint copy the rotation of any object, including a Spline. Add a Constraint Tag to the Joint and select PSR Constraint to follow position, scale, and rotation, or just Rotation if you want to limit it to rotation 🔄.
Step-by-Step Setup
Select the Joint and go to Tags / Constraint. In the Tag, add the Spline as Target. Check only Rotation if you don't want the Joint to copy position or scale. Adjust Weight to control how much the Spline's rotation is followed.
Considerations with Splines
Splines do not have rotation by default like normal 3D objects. For the Joint to follow correctly, you can use a Null object aligned to the Spline's tangent or combine Align to Spline Tag with the Constraint. It's like teaching a dog to walk in a straight line 🐶: if the path curves, it needs guidance to not get lost.