 
 
 	//energy conservation
-	diffuse_light *= 1.0-metallic; // TODO: avoid diffuse and ambient light calculations when metallic == 1
+	diffuse_light *= 1.0-metallic; // TODO: avoid all diffuse and ambient light calculations when metallic == 1 up to this point
 	ambient_light *= 1.0-metallic;
 
 

#endif

#if defined(LIGHT_USE_CLEARCOAT)

# if !defined(SPECULAR_SCHLICK_GGX) && !defined(SPECULAR_BLINN)
 		vec3 H = normalize(V + L);
# endif
# if !defined(SPECULAR_SCHLICK_GGX)
		float cNdotH = max(dot(N,H), 0.0);
		float cLdotH = max(dot(L,H), 0.0);
		float cLdotH5 = SchlickFresnel(cLdotH);
#endif
		float Dr = GTR1(cNdotH, mix(.1, .001, clearcoat_gloss));
		float Fr = mix(.04, 1.0, cLdotH5);
		float Gr = G_GGX_2cos(cNdotL, .25) * G_GGX_2cos(cNdotV, .25);


		specular_light += .25*clearcoat*Gr*Fr*Dr;
#endif
	}


	float NdotV = dot(N, V);
	float cNdotV = max(NdotV, 0.0);

	if (metallic < 1.0) {
#if defined(DIFFUSE_OREN_NAYAR)
		vec3 diffuse_brdf_NL;
#else
		float diffuse_brdf_NL; // BRDF times N.L for calculating diffuse radiance
#endif


#if defined(DIFFUSE_LAMBERT_WRAP)
		//energy conserving lambert wrap shader
		diffuse_brdf_NL = max(0.0,(NdotL + roughness) / ((1.0 + roughness) * (1.0 + roughness)));

#elif defined(DIFFUSE_OREN_NAYAR)

		{
			// see http://mimosa-pudica.net/improved-oren-nayar.html
			float LdotV = dot(L, V);


			float s = LdotV - NdotL * NdotV;
			float t = mix(1.0, max(NdotL, NdotV), step(0.0, s));

			float sigma2 = roughness * roughness; // TODO: this needs checking
			vec3 A = 1.0 + sigma2 * (- 0.5 / (sigma2 + 0.33) + 0.17*diffuse_color / (sigma2 + 0.13) );
			float B = 0.45 * sigma2 / (sigma2 + 0.09);

			diffuse_brdf_NL = cNdotL * (A + vec3(B) * s / t) * (1.0 / M_PI);
		}

#elif defined(DIFFUSE_TOON)

		diffuse_brdf_NL = smoothstep(-roughness,max(roughness,0.01),NdotL);

#elif defined(DIFFUSE_BURLEY)

		{


			vec3 H = normalize(V + L);
			float cLdotH = max(0.0,dot(L, H));

			float FD90 = 0.5 + 2.0 * cLdotH * cLdotH * roughness;
			float FdV = 1.0 + (FD90 - 1.0) * SchlickFresnel(cNdotV);
			float FdL = 1.0 + (FD90 - 1.0) * SchlickFresnel(cNdotL);
			diffuse_brdf_NL = (1.0 / M_PI) * FdV * FdL * cNdotL;
	/*
			float energyBias = mix(roughness, 0.0, 0.5);
			float energyFactor = mix(roughness, 1.0, 1.0 / 1.51);
			float fd90 = energyBias + 2.0 * VoH * VoH * roughness;
			float f0 = 1.0;
			float lightScatter = f0 + (fd90 - f0) * pow(1.0 - cNdotL, 5.0);
			float viewScatter = f0 + (fd90 - f0) * pow(1.0 - cNdotV, 5.0);

			diffuse_brdf_NL = lightScatter * viewScatter * energyFactor;*/
		}
#else
		//lambert
		diffuse_brdf_NL = cNdotL * (1.0 / M_PI);
#endif

#if defined(TRANSMISSION_USED)
		diffuse_light += light_color * diffuse_color * mix(vec3(diffuse_brdf_NL), vec3(M_PI), transmission) * attenuation;
#else
		diffuse_light += light_color * diffuse_color * diffuse_brdf_NL * attenuation;
#endif



#if defined(LIGHT_USE_RIM)
		float rim_light = pow(1.0-cNdotV, (1.0-roughness)*16.0);
		diffuse_light += rim_light * rim * mix(vec3(1.0),diffuse_color,rim_tint) * light_color;
#endif
	}


	if (roughness < 1.0) {


		// D
