#local Eps = 1E-6;

#declare ringwulst = 
    difference {
	difference {
	    union {
		cylinder {
		    <0, -10, 0>
		    <0,  10, 0>
		    50
		}
		torus {
		    50, 15
		    scale <1, 10/15, 1>
		}
	    }
	    cylinder {
		<0, -10 - Eps, 0>
		<0,  10 + Eps, 0>
		15
	    }
	}
	difference {
	    union {
		cylinder {
		    <0, -8, 0>
		    <0,  8, 0>
		    50
		}
		torus {
		    50, 13
		    scale <1, 8/13, 1>
		}
	    }
	    cylinder {
		<0, -8 - Eps, 0>
		<0,  8 + Eps, 0>
		17
	    }
	}
	box {
	    <-100, -100, -100>
	    <   0,  100,    0>
	}

	#if (0)
	texture {
	    crackle 
	    texture_map {
		[ 0.0 T_arkonstahl ]
		[ 0.2 T_arkonstahl ]
		[ 0.2 T_luft ]
		[ 1.0 T_luft ]
	    }
	}
	#else 
	texture { T_arkonstahl }
	#end
    }