The invention provides a computer implemented method for designing a part. The method comprises a step of providing a surface and a base curve lying on the surface. The method also comprises a step of sampling the base curve into a list of base points. The method also comprises a step of determining a grid of points of perpendicular geodesic curves. The points of the grid each belong to a respective level. Each level of the grid corresponds to a respective geodesic distance to the base curve. Each perpendicular geodesic curve lies on the surface and departs perpendicularly from the base curve at a respective base point. The method then comprises a step of computing a plurality of parallel geodesic curves lying on the surface by using the grid of points. Each parallel geodesic curve corresponds to a respective level. A representation of the part is displayed.