// Use v_modelPos from modelPos_pars_frag

#ifdef FLAT_SHADED
    vec3 fdx = dFdx(v_modelPos);
    vec3 fdy = dFdy(v_modelPos);
    vec3 N = normalize(cross(fdx, fdy));
#else
    vec3 N = normalize(v_Normal);
    #ifdef DOUBLE_SIDED
        N = N * (float(gl_FrontFacing) * 2.0 - 1.0);
    #endif
#endif

#ifdef USE_TBN
	vec3 tangent = normalize(v_Tangent);
	vec3 bitangent = normalize(v_Bitangent);
	#ifdef DOUBLE_SIDED
		tangent = tangent * (float(gl_FrontFacing) * 2.0 - 1.0);
		bitangent = bitangent * (float(gl_FrontFacing) * 2.0 - 1.0);
	#endif
	mat3 tspace = mat3(tangent, bitangent, N);
#endif

// non perturbed normal
vec3 geometryNormal = N;

#ifdef USE_NORMAL_MAP
    vec3 mapN = texture2D(normalMap, v_Uv).rgb * 2.0 - 1.0;
    mapN.xy *= normalScale;
    #ifdef USE_TBN
        N = normalize(tspace * mapN);
    #else
        mapN.xy *= (float(gl_FrontFacing) * 2.0 - 1.0);
        N = normalize(tsn(N, v_modelPos, v_Uv) * mapN);
    #endif
#elif defined(USE_BUMPMAP)
    N = perturbNormalArb(v_modelPos, N, dHdxy_fwd(v_Uv));
#endif

#ifdef USE_CLEARCOAT
	vec3 clearcoatNormal = geometryNormal;
#endif

#ifdef USE_CLEARCOAT_NORMALMAP
	vec3 clearcoatMapN = texture2D(clearcoatNormalMap, v_Uv).xyz * 2.0 - 1.0;
	clearcoatMapN.xy *= clearcoatNormalScale;

	#ifdef USE_TBN
		clearcoatNormal = normalize(tspace * clearcoatMapN);
	#else
		clearcoatMapN.xy *= (float(gl_FrontFacing) * 2.0 - 1.0);
		clearcoatNormal = normalize(tsn(clearcoatNormal, v_modelPos, v_Uv) * clearcoatMapN);
	#endif
#endif