Pattern "PxrSeExpr" "PxrSeExpr1"
		"float floatInput1" [0.5]  # outer rad
		"float floatInput2" [0.25] # inner rad
		"string expression"
		["d = dist(s-0.5,t-0.5,0, 0, 0, 0);\
		outer = (d < floatInput1) ? 1 : 0;\
		d = dist(s-0.5,t-0.5,0, 0, 0, 0);\
		inner = (d < floatInput2) ? 0 : 1;\
		resultF = outer * inner;\
		resultF\
		"]
		#d = dist(s, t, 0   x, y, z)


Bxdf "PxrSurface" "PxrSurface1"
		#"float inputMaterial" []
		"float diffuseGain" [0]
		"color diffuseColor" [1 1 1]
		"int diffuseDoubleSided" [1]
		"int specularFresnelMode" [1]
		"color specularEdgeColor" [0.9 0.9 0.9]
		"color specularIor" [0.155 0.117 0.138]
		"color specularExtinctionCoeff" [4 4 4]
		"float specularRoughness" [0.4]
		"float glassIor" [1.1]
		"int specularDoubleSided" [0]
		"reference float presence" ["PxrSeExpr1:resultF"]