“…The Azimuthal Equidistant Projection (AEP) is able to project normals onto points in a Euclidean space according to the direction. It has previously been employed to capture the local variations in facial shape [23], and can be applied to the normals, in order to project each 3D direction into the position in a Euclidean 2D plane. So for a regular grid of normals, defined as n(i, j) = (u i, j , v i, j , w i, j ), the AEP point p(i, j) = (x i, j , y i, j ) in this plane is defined as:…”