surface
test_gather(float invert			  = 0,
				  swap 				  = 0,
				  Ks                  = 1,
				  refractive_index = 1.52,
				  samplecone          = 0,
				  samples             =10)
{
vector  i = normalize(I);
normal  n = normalize(N);
normal  nf = faceforward(n, i);
color   hitcol = 0;

float refIndex = refractive_index;

float sc = ((2 * PI)/360) * samplecone;

Ci = 0;
Oi = Os;


		if(invert == 0){

				if(n.-i < 0){

						refIndex = 1/refIndex;
		}else{
				if(n.-i < 0){
	
						refIndex = refIndex;
}
}
}




vector rayRef = refract(i, nf, refIndex);

float numhits = 0;

gather("illuminance", P, rayRef, sc, samples, "surface:Ci", hitcol)
			{
				Ci += hitcol;
				numhits += 1;
			}


Ci = (Ci / numhits);
Oi = 1;

}