Logic of "Edges From Directions" on non-linear curves/swept edges?

Grasshopper
1

What if the edges are not linear v0.gh (31.6 KB)

Hi everyone,

I am looking for technical clarification on the internal logic of the native Grasshopper component “Edges From Directions” (Surface > Util).

When the input Brep contains non-linear edges (curves, arcs, or splines), how does the component determine the “direction” of that edge to compare it against the target vector (D)?

I have observed inconsistent results when working with swept surfaces. Specifically, I would like to know:

  1. Sampling Point: Does the component evaluate the tangent at t=0 (Start), t=0.5 (Mid-parameter), or does it use a Chord Vector (End - Start)?
  2. Domain Sensitivity: Does the “Reparameterize” state of the input Brep edges affect the direction calculation?
  3. Closed Loops: How does it handle closed edges (like the circular edge of a cylinder) where the start and end points coincide?

In my current workflow (selecting edges from a swept Brep), some geometrically parallel edges are being ignored, possibly due to flipped curve directions or sampling point discrepancies.

If anyone (or the developers) could shed light on the exact RhinoCommon method used behind this component, it would be greatly appreciated!

Thanks in advance.

image
image2125×763 90.2 KB

2

Hello?

3

There are no info on that, it is not done through direct api method. You have to conduct experiments to find out