Parametric Surface-Surface Intersect

Marching methods

Reference : Why CAD Surface Geometry is Inexact

Incremental progression along the intersection curve.
This method use starting points on the intersection curve to obtain new points evaluating the tangent direction of the curve.

1. search for starting points for every intersection curve，can use the subdivision method.
   

2. The marching process first-order ordinary differential equations
   

3. curve fitting

The numerical intersection algorithms introduce gaps and openings at the best-fit curves representing the intersections, making the resulting surfaces non-watertight.