How to Use Tangents from a Mesh Line to Align Feathers on a 3D Tail Mesh in Blender Geometry Nodes?

Question

I'm working on a Blender project where I need to distribute and align feathers along a 3D tail. The tail starts as a simple mesh line, and I apply Skin and Subdivision Surface modifiers to turn it into a 3D mesh. The challenge is that I want the feathers rotation to follow the direction (tangent) of the original mesh line, not just rely on normals, which don't give the correct orientation in this case.

The setup I want:

-Everything should remain procedural and non-destructive. -I need the feathers to align with the tangent of the original curve (the mesh line) as the tail bends and moves.

My question: How can I extract the tangent information from the original mesh line (before it’s turned into a 3D object) and use it to align the feathers along the final 3D tail in Blender Geometry Nodes? I’m struggling with getting the feathers to align properly and flow down the tail naturally as it moves and bends.

Any suggestions or node setups would be really helpful!

Answer 1

You can use curves object to setup feathers along mesh. The only requirement for this setup is you have to have non-overlapping UV (at least generated) on the surface mesh.

Look at my setup. I've used basic modifiers to drive curves, such as Interpolate Hair Curves, Smooth Hair Curves and Surface Deform:

Surface Deform is important here, because it allows to animate the base mesh and feathers will follow mesh surface animation.

Then in last modifier I made a setup that replaces curves by feathers:

I've used Sample curve to sample the tangent vector from the middle of the curve, and used surface_normal attribute, which is stored by Interpolate Hair Curves

Tangent vector makes feathers follow direction, while surface normal is useful to rotate it along the axis parallel to the surface

Using this setup, you can drive feathers using the Sculpt mode of the Curves object.