Freehand 3D Curve Recognition and Oversketching

Abstract

In the CAD/CAS field, the increasing domination of spline-based graphic objects has driven a great attention to methods focusing on the management of free-form curves. Based on the quick brainstorm illustration and stepwise refinement characteristics in conceptual designing stage, we present a method, which automatically reconstructs the designer s free-form 3D curve through recognizing his design intention . This algorithm automatically extracts the relevant control points through corner detection and dynamic-threshold sampling mechanism; as a result the Bspline curve is approximately produced. Furthermore, considering the ambiguity of designer s intention during the conceptual designing, this redraw operation feature is implemented through the so-called over-sketching . For this we introduce constrained length and tangent angle features, which supports fully free form 3D curve sketching, and it is capable of effectively smoothen transition interval. The method has been tested with various types of sketches, which are rendered in 3D scene environment. We further discuss the modification and its application to surfaces.