A one-triangle test of drop-cutter for toroidal tools (a.k.a. filleted-endmills, or bull-nose).
The blue points are contacts with the facet, and the green points are contacts with the vertices. These are easy.
The edges-contacts (red-points) are a bit more involved, and are done with the offset-ellipse solver presented earlier here(the initial geometry) and here(offset-ellipse construction) and here(convergence of the solver) and here(toroid-line intesection animation).