pub fn connect_bdpt<'a>(
    scene: &'a Scene,
    light_vertices: &[Vertex<'a>],
    camera_vertices: &[Vertex<'a>],
    s: usize,
    t: usize,
    light_distr: Arc<Distribution1D>,
    camera: &'a Arc<Camera>,
    sampler: &mut Sampler,
    p_raster: &mut Point2f,
    mis_weight_opt: Option<&mut Float>
) -> Spectrum