Posted by dxli on Oct 19, 2024; 8:03pm
URL: https://forum.librecad.org/cannot-snap-intersection-of-two-inscribed-ellipses-tp5725436p5725476.html

in 2.2.1, added new algorithm to recover tangent points within tolerance(1e-5 of the curve length).

if two curves are found within this distance, the offset of one curve is used to locate the tangent point.

For example, if two tangent circles doesn't have an intersection, due to rounding errors. For the CAD engine, there's a gap of 1e-9 between them. Slighly increase the radius of the smaller circle by 2e-9, and the intersections can be now found using the enlarged circle and the other circle.

The algorithm uses bisection to find the optimum shape/position changes to locate a tangent point.

The clear drawback, if the two circles are actually separated by a gap of 1e-9, a tangent point will still be found, but it's less problematic, compared with failure in finding an actual tangent point.