//> the compiler should be able to optimize the following branch
					if(isMesh){
						vec2 invSize = 1.0 / texSize;\
						vec4 uvOffset = vec4(1.0, 0.0, 0.0, 1.0) * vec4(invSize, invSize);\
						vec4 c1 = texture2D( maskTexture, vUv + uvOffset.xy);\
						vec4 c2 = texture2D( maskTexture, vUv - uvOffset.xy);\
						vec4 c3 = texture2D( maskTexture, vUv + uvOffset.yw);\
						vec4 c4 = texture2D( maskTexture, vUv - uvOffset.yw);\
						float diff1 = (c1.r - c2.r)*0.5;\
						float diff2 = (c3.r - c4.r)*0.5;\
						float d = length( vec2(diff1, diff2) );\
						float a1 = min(c1.g, c2.g);\
						float a2 = min(c3.g, c4.g);\
						float visibilityFactor = min(a1, a2);\
						vec3 edgeColor = 1.0 - visibilityFactor > 0.001 ? visibleEdgeColor : hiddenEdgeColor;\
						gl_FragColor = vec4(edgeColor, 1.0) * vec4(d);\
					} else {
						vec4 edge = texture2D( maskTexture, vUv);
						vec3 edgeColor = 1.0 - edge.g > 0.001 ? visibleEdgeColor : hiddenEdgeColor;
						gl_FragColor = vec4( edgeColor, 1.0) * (1.0-edge.r);
					}