Q2: Our algorithm agreed with the majority of participants on all but 1 out of 40 curve queries. The anomalous curve was one of the 7 curves that could be classified as tangent plane or shell projection. In these cases, our algorithm uses the shape of the 2D stroke to distinguish the two types. A near straight line stroke in keeping with the non-accidental viewpoint assumption is classified as tangent plane and others as shell projections. Designers can readily create the alternate interpretation in our system using the shift key. In many cases the geometric difference in the resulting 3D curve between these two interpretations is also subtle.