bool _hit_two_sided_intersection(Ray const& ray_wld, ObjectIntersections* hit, ObjectBase const* object, int num_forward_roots, Float d0,Float d1) {
    //There are six cases that we need to consider.  ASCII art drawn for a sphere.                   /    ___
    //  Case A:                                                                                     +    /   \
    //      Ray does not intersect object at all.        ray origin: +       ahead: =             //    |     |
    //      Zero forward roots.                        intersection: X    backward: -            L       \___/
    //                                                         both: *                                    ___
    //  Case B:                                                                                          /   \
    //      Ray intersects object ahead of it (once the front side, once the back side).       ----+====X=====X==>
    //      Two forward roots.                                                                           \___/
    //                                                                                                    ___
    //  Case C:                                                                                          /   \
    //      Ray is on the surface heading into the object.                                          ----*=====X==>
    //      One or two forward roots (first root may not be counted).                                    \___/
    //                                                                                                    ___
    //  Case D:                                                                                          /   \
    //      Ray starting inside the object.                                                         ----X--+==X==>
    //      One forward root.                                                                            \___/
    //                                                                                                    ___
    //  Case E:                                                                                          /   \
    //      Ray is on the surface heading away from object.                                         ----X-----*==>
    //      Zero or one forward roots (second root may not be counted).                                  \___/
    //                                                                                                    ___
    //  Case F:                                                                                          /   \
    //      Ray is outside the object heading away.  Two intersections behind.                      ----X-----X----+==>
    //      Zero forward roots.                                                                          \___/

    if (num_forward_roots>0) {
        //Case B, C, D, or some Es
        if (ray_wld.orig.object==object) {
            //Case C, D, or some Es
            if (d0<static_cast<Float>(-0.000001)) { //The first root is well behind us
                //Case D or some Es
                if (d1<static_cast<Float>(0.000001)) {
                    //Case some Es
                    assert(num_forward_roots==0||num_forward_roots==1,"Implementation error!");
                    //    Ignore "d0" far behind us and "d1" we're leaving from
                } else {
                    //Case D
                    assert(num_forward_roots==1,"Implementation error!");
                    //    Ignore "d0" far behind us
                    hit->add(object, d1, ray_wld.t);
                    return true;
                }
            } else {
                //Case C
                assert(num_forward_roots==1||num_forward_roots==2,"Implementation error!");
                //    Ignore front surface hit "d0".
                hit->add(object, d1, ray_wld.t);
                return true;
            }
        } else {
            //Case B
            assert(num_forward_roots==2,"Implementation error!");
            hit->add(object, d0, ray_wld.t);
            hit->add(object, d1, ray_wld.t);
            return true;
        }
    } else {
        //Case A, some Es, or F
    }
    return false;
}