diff --git a/shaders/lib/shading-pbr.glsl b/shaders/lib/shading-pbr.glsl
index 269f16f..53cf840 100644
--- a/shaders/lib/shading-pbr.glsl
+++ b/shaders/lib/shading-pbr.glsl
@@ -13,6 +13,12 @@ struct T_PBRMaterial
 	float specularTint;	// Albedo color% in specular tint (non-metals)
 };
 
+struct T_PBRPrecomputed
+{
+	float nDotV , ax , ay , fv , vgs;
+	vec3 tangent , bitangent , cSpecular;
+};
+
 // -----------------------------------------------------------------------------
 
 float PBR_SchlickFresnel(
@@ -46,66 +52,93 @@ float PBR_SmithGGXAniso(
 	return 1 / ( nDotV + sqrt( x * x + y * y + nDotV * nDotV ) );
 }
 
+T_PBRPrecomputed PBR_Precompute(
+	in T_PBRMaterial material ,
+	in vec3 camDir ,
+	in vec3 normal )
+{
+	T_PBRPrecomputed rv;
+
+	rv.nDotV = dot( normal , camDir );
+	rv.fv = PBR_SchlickFresnel( rv.nDotV );
+
+	float tDir = step( .99 , abs( normal.z ) ) ,
+		aspect = sqrt( 1 - material.anisotropy * .9 ) ,
+		rsqr = material.roughness * material.roughness;
+
+	vec3 tUp = mix( vec3( 0 , 0 , 1 ) , vec3( 1 , 0 , 0 ) , tDir ) ,
+		tint = M_NormalizeColor( material.cAlbedo );
+	rv.tangent = normalize( cross( tUp , normal ) );
+	rv.bitangent = normalize( cross( normal , rv.tangent ) );
+
+	rv.cSpecular = mix(
+		material.specular * .08 * mix(
+			vec3( 1 ) , tint , material.specularTint ) ,
+		material.cAlbedo , material.metallic );
+
+	rv.ax = max( .001, rsqr / aspect );
+	rv.ay = max( .001, rsqr * aspect );
+	rv.vgs = PBR_SmithGGXAniso( rv.nDotV ,
+		dot( camDir , rv.tangent ) , dot( camDir , rv.bitangent ) ,
+		rv.ax , rv.ay );
+
+	return rv;
+}
+
 vec3 PBR_Shade(
 	in T_PBRMaterial material ,
+	in T_PBRPrecomputed pre ,
 	in vec3 camDir ,
 	in vec3 normal ,
 	in vec3 lightDir )
 {
-	float nDotL = dot( normal , lightDir ) ,
-		nDotV = dot( normal , camDir );
-	if ( nDotL < 0 || nDotV < 0 ) {
+	float nDotL = dot( normal , lightDir );
+	if ( nDotL < 0 || pre.nDotV < 0 ) {
 		return vec3( 0 );
 	}
 
-	vec3 tangent = cross( vec3( 0 , 1 , 0 ) , normal );
-	if ( length( tangent ) == 0 ) {
-		tangent = cross( vec3( 1 , 0 , 0 ) , normal );
-	}
-	tangent = normalize( tangent );
-	vec3 bitangent = normalize( cross( normal , tangent ) );
-
-	vec3 halfVec = normalize( lightDir + camDir ) ,
-		tint = M_NormalizeColor( material.cAlbedo ) ,
-		cSpecular = mix( material.specular * .08 * mix(
-				vec3( 1 ) , tint , material.specularTint ) ,
-			material.cAlbedo , material.metallic );
-	//vec3 Csheen = mix(vec3(1), Ctint, sheenTint);
-
+	vec3 halfVec = normalize( lightDir + camDir ) ;
 	float nDotH = dot( normal , halfVec ) ,
 		lDotH = dot( lightDir , halfVec ) ,
 
 	// Diffuse fresnel - go from 1 at normal incidence to .5 at grazing
 	// and mix in diffuse retro-reflection based on roughness
 		FL = PBR_SchlickFresnel( nDotL ) ,
-		FV = PBR_SchlickFresnel( nDotV ) ,
 		Fd90 = 0.5 + 2 * lDotH * lDotH * material.roughness ,
-		Fd = mix( 1 , Fd90 , FL ) * mix( 1 , Fd90 , FV ) ,
+		Fd = mix( 1 , Fd90 , FL ) * mix( 1 , Fd90 , pre.fv ) ,
 
 	// Based on Hanrahan-Krueger brdf approximation of isotropic bssrdf
 	// 1.25 scale is used to (roughly) preserve albedo
 	// Fss90 used to "flatten" retroreflection based on roughness
 		Fss90 = lDotH * lDotH * material.roughness ,
-		Fss = mix( 1 , Fss90 , FL ) * mix( 1 , Fss90 , FV ) ,
-		ss = 1.25 * ( Fss * ( 1 / ( nDotL + nDotV ) - .5 ) + .5 ) ,
+		Fss = mix( 1 , Fss90 , FL ) * mix( 1 , Fss90 , pre.fv ) ,
+		ss = 1.25 * ( Fss * ( 1 / ( nDotL + pre.nDotV ) - .5 ) + .5 ) ,
 
 	// Specular
-		aspect = sqrt( 1 - material.anisotropy * .9 ) ,
-		rsqr = material.roughness * material.roughness ,
-		ax = max( .001, rsqr / aspect ) ,
-		ay = max( .001, rsqr * aspect ) ,
-		Ds = PBR_GTR2Aniso( nDotH , dot( halfVec , tangent ) ,
-				dot( halfVec , bitangent ) , ax , ay ) ,
+		Ds = PBR_GTR2Aniso( nDotH , dot( halfVec , pre.tangent ) ,
+				dot( halfVec , pre.bitangent ) ,
+				pre.ax , pre.ay ) ,
 		FH = PBR_SchlickFresnel( lDotH ) ,
-		Gs  = PBR_SmithGGXAniso( nDotL , dot( lightDir , tangent ) ,
-				dot( lightDir , bitangent ) , ax , ay )
-			* PBR_SmithGGXAniso( nDotV , dot( camDir , tangent ) ,
-					dot( camDir , bitangent ) , ax , ay );
+		Gs  = PBR_SmithGGXAniso( nDotL , dot( lightDir , pre.tangent ) ,
+				dot( lightDir , pre.bitangent ) ,
+				pre.ax , pre.ay ) * pre.vgs;
 
-	vec3 Fs = mix( cSpecular , vec3(1) , FH );
+	vec3 Fs = mix( pre.cSpecular , vec3(1) , FH );
 	return nDotL * ( ( ( 1 / PI )
 			* mix( Fd , ss , material.subsurface )
 			* material.cAlbedo /* + Fsheen */)
 			* pow( 1 - material.metallic , 3 )
 		+ clamp( Gs , 0 , 1 ) * Fs * Ds );
 }
+
+vec3 PBR_Shade(
+	in T_PBRMaterial material ,
+	in vec3 camDir ,
+	in vec3 normal ,
+	in vec3 lightDir )
+{
+	return PBR_Shade(
+		material ,
+		PBR_Precompute( material , camDir , normal ) ,
+		camDir , normal , lightDir );
+}
diff --git a/shaders/scene.f.glsl b/shaders/scene.f.glsl
index d938dbc..fd92d75 100644
--- a/shaders/scene.f.glsl
+++ b/shaders/scene.f.glsl
@@ -65,6 +65,7 @@ vec2 RM_Map( vec3 pos )
 
 vec3 pointlight(
 	in T_PBRMaterial material ,
+	in T_PBRPrecomputed pre ,
 	in vec3 hitPos ,
 	in vec3 rayDir ,
 	in vec3 normal ,
@@ -79,7 +80,7 @@ vec3 pointlight(
 	}
 
 	return lightColor * lPwr * PBR_Shade(
-			material , -rayDir , normal , lightRay );
+			material , pre , -rayDir , normal , lightRay );
 }
 
 
@@ -123,11 +124,15 @@ void main( )
 					-rayDir , normal , sunlightDir );
 		} else {
 			T_PBRMaterial mat = PBRMaterials[ mtidx ];
-			bc = sunlightColor * PBR_Shade( mat ,
+			T_PBRPrecomputed pre = PBR_Precompute(
+					mat , -rayDir , normal );
+			bc = sunlightColor * PBR_Shade( mat , pre ,
 					-rayDir , normal , sunlightDir );
-			bc += pointlight( mat , hitPos , rayDir , normal ,
+			bc += pointlight( mat , pre ,
+					hitPos , rayDir , normal ,
 					pl1Pos , pl1Color , pl1Power );
-			bc += pointlight( mat , hitPos , rayDir , normal ,
+			bc += pointlight( mat , pre ,
+					hitPos , rayDir , normal ,
 					pl2Pos , pl2Color , pl2Power );
 		}