1. A method performed by a product data management (PDM) data processing system, comprising: receiving a graphic model having a plurality of curves forming a curve chain; defining a distance threshold and angle threshold corresponding to the graphical model; optimizing the curve chain under shape constraints, including selecting two of the plurality of curves of the curve chain, adjusting a control point at a curve end of each of the selected curves to a point in the middle of the curve ends, and adjusting a second control point of each of the selected curves by projecting each second control point to a gap angle bisector between the selected curves; identifying a surface associated with the curve chain; optimizing the curve chain with under surface and distance constraints with respect to the identified surface; and storing the graphical model with the optimized curve chain.