I’m trying to draw an arc on a surface and I’m confused by the **Arc by Center, Normal, Radius** node; there is no normal input, so I assume it gets bundled with the center input somehow: for the **center** input, the tooltip says “XYZ or Coordinate System”–but I have not been able to discover what a Coordinate System is.

I’ve tried feeding it a plane (nothing), a [point,normal] pair in a list (draws an arc, but doesn’t use the normal), and a [normal, point] pair (same results).

Any explanation would be appreciated . . .