QSolid Demos：

1.BiArc Fitting： based on the specified tolerance, to fit any 2d curve with many small arcs, at very few positions, with lines instead.

the following left pictures is original spline curves, the right pictures is the arcs fitted to the original spline curves.

2.Fill Surface： given the boundary curves, and specify the shape control curves inside the boundary, fill the surface.

the tolerance can satisfy the practical use.