surface
test_vis1(float    Kd = 1,         
                   visToCamera = 1,
                   visToOthers = 1, 
                   visibility = 0,
				   minimum    = 0,
				   maximum    = 2;
		  color    surfaceColor = (1,1,1))
{

normal  n = normalize(N);
normal  nf = faceforward(n, I);
string  typename = "unknown";
color   diffusecolor, surfcolor = surfaceColor;


rayinfo("type", typename);

float isCameraRay = (typename == "camera") ? 1 : 0;

if((isCameraRay == 1 && visToCamera == 1) ||
   (isCameraRay == 0 && visToOthers == 1)){

    diffusecolor = Kd * diffuse(nf);
    Oi = Os;
    Ci = Oi  * Cs * diffusecolor * surfcolor;

    }
else 
    {

	Ci = 0;
	Oi = 0;
	if(n != nf){	
				float vis = smoothstep(minimum, maximum, length(I));
				
					diffusecolor = Kd * diffuse(nf); 
                    Oi = vis;				
                    Ci = Oi * mix(color trace(P,I),Cs,Oi) * diffusecolor * surfcolor;
}
}
}