How does the Offset command know on which side of the curve the mouse is located?

[mrhe (Mariusz Hermansdorfer)]

@siemen

I’m after the relation between a point and a curve instead of the location of where the mouse is.

You could use the built-in Curve.Contains method to check whether a point is inside, outside or on a curve. Or you could use the winding number approach as described here:

C# Create a mesh with a hole inside

Thanks @Petras_Vestartas! In the meantime I have implemented the winding number approach from this paper as suggested by @laurent_delrieu. It is almost 10 times faster than the Curve.Contains method. [image] public static bool PointInPolygon(Point3d p, Point3d[] polylineArray) { int n = polylineArray.Length - 1; int windingNumber = 0; // the winding number counter // loop through all edges of the polygon for (int i = 0; i < n; i++) { // …