Create a set of equally spaced curve contour points.

Input parameters:

1. Cv → Curve to contour.
2. Pt → Contour base point
3. Nr → Contour slice normal direction.
4. Sp → Spacing between contour layers.

Output parameters:

1. Ct → Contour points, sorted by layer.
2. Lc → Loci of contour points on the curve.
3. Ly → Layer, i.e. contour section offset, given as an integer. Layer zero is the section through the base point.