 	}
 	
 	// relative Fresnel Factor
-	float F = getFresnelFactorAbsolute(K1, K2);
+	float F = fFByR0;
 	F = F*F;
 //	float cosNumNumSamples = cos(thetaR)*dimN*dimN;
 	float cosNumNumSamples = 1.0;

	float vv0 = _k1.y - _k2.y;
	float ww = _k1.z - _k2.z;	
	
	float fF = getFresnelFactorAbsolute(_k1, _k2);
	float nSkin = 1.5;
	float R0 = pow( (nSkin - 1.0) / (nSkin + 1.0) , 2.0); 
	
	fFByR0 = fF/R0;
	float shadowF = getShadowMaskFactor(_k1, _k2);

	vec3 V = vec3(uu0, vv0, ww);

	vec2 N_uv[2] = vec2[2](N_u, N_v);
	vec2 modUV = getRotation(u,v,phi);
	

	float iterMax = 500.0;
	float lambdaStep = (lambda_max - lambda_min)/(iterMax-1.0);
	float F2 = fFByR0*fFByR0;
	
