pub fn spot_lit_specular(
    location: impl Into<Point3>,
    target: impl Into<Point3>,
    specular_exponent: scalar,
    cutoff_angle: scalar,
    light_color: impl Into<Color>,
    surface_scale: scalar,
    ks: scalar,
    shininess: scalar,
    input: impl Into<Option<ImageFilter>>,
    crop_rect: impl Into<CropRect>
) -> Option<ImageFilter>