shader ShapedScatter(color Color = 0.0, float Density = 1.0, float Anisotropy = 0.0, float Fac = 0.5, float Lower = 0.0, float Upper = 1.0, output closure color Volume = holdout(), output color Complement = 0.0, output float Threshold = 0.0) {
    Complement = transformc("rgb", "hsv", Color);
    Complement[0] = mod(Complement[0] + 0.5, 1.0);
    Complement = transformc("hsv", "rgb", Complement);
    Threshold = threshold(Fac, Lower, Upper);
    Volume = mix(holdout(), Complement * Density * henyey_greenstein(Anisotropy), Threshold);
    Complement = mix(0.0, Complement, Threshold);
}