Curve.curvature: 2d cross product needs an absolute sign

[darikg]

I was a little surprised to see Curve.curvature returning negative values when the documentation defines the curvature as the ratio of two vector magnitures. Looking into it a little bit, it looks like np.cross returns a scalar for 2d input vectors, (as the comments in Curve.curvature said), but because that scalar component is the z-component of the cross product, this can be positive or negative, so we should take the absolute value of this.

[VikingScientist]

Good catch and thanks for the contribution 😄 👍