And when I am on the curve I am on the boundary of the surface, so there is a direction along the surface that is the curve and the other one is pointing into the surface.

And we looked at the component of a vector field in the direction that was normal to the curve.

Firstly, using the first order derivative of Gaussian function as the base wavelet, the direction Angle function of a planar curve was analyzed on multiple scales to obtain the candidates of corners.