Function trace_tangential 

pub fn trace_tangential(
    a: &SurfaceGeometry,
    b: &SurfaceGeometry,
    from: Contact,
    options: Marching,
    tol: Tolerances,
) -> OgeomResult<Traced>

Trace the tangential contact of two surfaces through a seed.

The seed need only be near the contact: it is first corrected onto it. The trace walks both ways from there (see the module documentation for the predictor and the corrector) and stops where the contact closes, runs off either surface’s domain, or ends: where the surfaces part by more than a hundred confusion distances, where their normals part by more than a branch point’s sine, or where the contact has no direction to follow (an isolated touch, a degenerate chart). Every point it returns was measured against both conditions.

Errors

OgeomError::Construction if the settings are unusable, the surfaces cross at the seed rather than touch, or the seed corrects to no contact: the surfaces come near there without touching, or touch at an isolated point.