Once classified, the curve-type defines how the 2D stroke should be interpreted in 3D. Points on a shell contour for example, typically lie above their corresponding 3D contour point on the underlying geometry at a height equal to their projected distance in 2D. The general viewpoint assumption that the 2D stroke is strongly indicative of its 3D shape [Nakayama and Shimojo 1992; Xu et al. 2014], provides us with a good metric to evaluate such a 3D interpretation of a stroke. Incorrectly classified strokes, typically result in 3D curves of poor quality. We default these strokes to projections on 3D planes commonly employed in sketch-based modeling [Bae et al. 2008; Schmidt et al. 2009]. These insights form the foundation of our novel 2D stroke to 3D curve inference algorithm (Section 3).