The reported Freestyle warnings were due to wrong normals of filled faces at both ends of a 2D extruded curve. The problem is detailed in the comment #19 of T39669. The cause of the bug was an inconsistency in the use of vertex indices between BKE_mesh_nurbs_displist_to_mdata() and init_render_curve() in the case of DispList::type equal to DL_INDEX3. This commit also fixes a related bug that the normals of filled faces were not inverted when a scale of the curve object is set to a negative value (e.g., the Z scale was -1). Reviewers: campbellbarton Reviewed By: campbellbarton Differential Revision: https://developer.blender.org/D532