Function plan_overlap 

pub fn plan_overlap(
    a: &ExactBRep,
    b: &ExactBRep,
    tolerance: Tolerance,
) -> Result<PlanOverlap, ExactMeasureError>

Whether the plan projections of a and b overlap over a patch of positive area, are certainly apart, or neither could be shown (#217).

Overlap is shown by two planar faces, one of each body, not vertical, whose shadows share an open patch: a slab under a column’s base, two slabs, a beam’s soffit over a wall’s top. Curved faces never show it; their shadows are still measured by plan_boundary_distance.

Errors

As boundary_distance.