Function sphere_against_field 

pub fn sphere_against_field(
    body: &RigidBody<EuclideanR3>,
    geometry: &GeometryStore,
    field: &dyn DistanceField,
    _space: &EuclideanR3,
) -> Result<FieldContact<EuclideanR3>, FieldRefusal>

Separation is the field distance at the sphere’s center minus its radius; the field must be an exact distance.