#define M_PI        3.14159265358979323846  /* pi */
#define M_2PI       6.28318530717958647692  /* 2*pi */
#define M_PI_2      1.57079632679489661923  /* pi/2 */
#define M_1_PI      0.318309886183790671538  /* 1/pi */
#define M_1_2PI     0.159154943091895335768  /* 1/(2*pi) */
#define M_1_PI2     0.101321183642337771443  /* 1/(pi^2) */

#define LUT_SIZE 64

/* Buffers */
uniform sampler2D colorBuffer;
uniform sampler2D depthBuffer;
uniform sampler2D maxzBuffer;
uniform sampler2D minzBuffer;
uniform sampler2DArray planarDepth;

#define cameraForward   normalize(ViewMatrixInverse[2].xyz)
#define cameraPos       ViewMatrixInverse[3].xyz
#define cameraVec      ((ProjectionMatrix[3][3] == 0.0) ? normalize(cameraPos - worldPosition) : cameraForward)
#define viewCameraVec  ((ProjectionMatrix[3][3] == 0.0) ? normalize(-viewPosition) : vec3(0.0, 0.0, 1.0))

/* ------- Structures -------- */

/* ------ Lights ----- */
struct LightData {
	vec4 position_influence;      /* w : InfluenceRadius */
	vec4 color_spec;              /* w : Spec Intensity */
	vec4 spotdata_radius_shadow;  /* x : spot size, y : spot blend, z : radius, w: shadow id */
	vec4 rightvec_sizex;          /* xyz: Normalized up vector, w: area size X or spot scale X */
	vec4 upvec_sizey;             /* xyz: Normalized right vector, w: area size Y or spot scale Y */
	vec4 forwardvec_type;         /* xyz: Normalized forward vector, w: Lamp Type */
};

/* convenience aliases */
#define l_color        color_spec.rgb
#define l_spec         color_spec.a
#define l_position     position_influence.xyz
#define l_influence    position_influence.w
#define l_sizex        rightvec_sizex.w
#define l_sizey        upvec_sizey.w
#define l_right        rightvec_sizex.xyz
#define l_up           upvec_sizey.xyz
#define l_forward      forwardvec_type.xyz
#define l_type         forwardvec_type.w
#define l_spot_size    spotdata_radius_shadow.x
#define l_spot_blend   spotdata_radius_shadow.y
#define l_radius       spotdata_radius_shadow.z
#define l_shadowid     spotdata_radius_shadow.w

/* ------ Shadows ----- */
#ifndef MAX_CASCADE_NUM
#define MAX_CASCADE_NUM 4
#endif

struct ShadowData {
	vec4 near_far_bias_exp;
	vec4 shadow_data_start_end;
	vec4 contact_shadow_data;
};

struct ShadowCubeData {
	vec4 position;
};

struct ShadowCascadeData {
	mat4 shadowmat[MAX_CASCADE_NUM];
	vec4 split_start_distances;
	vec4 split_end_distances;
};

/* convenience aliases */
#define sh_near   near_far_bias_exp.x
#define sh_far    near_far_bias_exp.y
#define sh_bias   near_far_bias_exp.z
#define sh_exp    near_far_bias_exp.w
#define sh_bleed  near_far_bias_exp.w
#define sh_tex_start    shadow_data_start_end.x
#define sh_data_start   shadow_data_start_end.y
#define sh_multi_nbr    shadow_data_start_end.z
#define sh_blur         shadow_data_start_end.w
#define sh_contact_dist            contact_shadow_data.x
#define sh_contact_offset          contact_shadow_data.y
#define sh_contact_spread          contact_shadow_data.z
#define sh_contact_thickness       contact_shadow_data.w

/* ------- Convenience functions --------- */

vec3 mul(mat3 m, vec3 v) { return m * v; }
mat3 mul(mat3 m1, mat3 m2) { return m1 * m2; }
vec3 transform_direction(mat4 m, vec3 v) { return mat3(m) * v; }
vec3 transform_point(mat4 m, vec3 v) { return (m * vec4(v, 1.0)).xyz; }
vec3 project_point(mat4 m, vec3 v) {
	vec4 tmp = m * vec4(v, 1.0);
	return tmp.xyz / tmp.w;
}

#define min3(a, b, c)                   min(a, min(b, c))
#define min4(a, b, c, d)                min(a, min3(b, c, d))
#define min5(a, b, c, d, e)             min(a, min4(b, c, d, e))
#define min6(a, b, c, d, e, f)          min(a, min5(b, c, d, e, f))
#define min7(a, b, c, d, e, f, g)       min(a, min6(b, c, d, e, f, g))
#define min8(a, b, c, d, e, f, g, h)    min(a, min7(b, c, d, e, f, g, h))
#define min9(a, b, c, d, e, f, g, h, i) min(a, min8(b, c, d, e, f, g, h, i))

#define max3(a, b, c)                   max(a, max(b, c))
#define max4(a, b, c, d)                max(a, max3(b, c, d))
#define max5(a, b, c, d, e)             max(a, max4(b, c, d, e))
#define max6(a, b, c, d, e, f)          max(a, max5(b, c, d, e, f))
#define max7(a, b, c, d, e, f, g)       max(a, max6(b, c, d, e, f, g))
#define max8(a, b, c, d, e, f, g, h)    max(a, max7(b, c, d, e, f, g, h))
#define max9(a, b, c, d, e, f, g, h, i) max(a, max8(b, c, d, e, f, g, h, i))

#define avg3(a, b, c)                   (a + b + c) * (1.0 / 3.0)
#define avg4(a, b, c, d)                (a + b + c + d) * (1.0 / 4.0)
#define avg5(a, b, c, d, e)             (a + b + c + d + e) * (1.0 / 5.0)
#define avg6(a, b, c, d, e, f)          (a + b + c + d + e + f) * (1.0 / 6.0)
#define avg7(a, b, c, d, e, f, g)       (a + b + c + d + e + f + g) * (1.0 / 7.0)
#define avg8(a, b, c, d, e, f, g, h)    (a + b + c + d + e + f + g + h) * (1.0 / 8.0)
#define avg9(a, b, c, d, e, f, g, h, i) (a + b + c + d + e + f + g + h + i) * (1.0 / 9.0)

float min_v2(vec2 v) { return min(v.x, v.y); }
float min_v3(vec3 v) { return min(v.x, min(v.y, v.z)); }
float max_v2(vec2 v) { return max(v.x, v.y); }
float max_v3(vec3 v) { return max(v.x, max(v.y, v.z)); }

float sum(vec2 v) { return dot(vec2(1.0), v); }
float sum(vec3 v) { return dot(vec3(1.0), v); }
float sum(vec4 v) { return dot(vec4(1.0), v); }

float saturate(float a) { return clamp(a, 0.0, 1.0); }
vec2 saturate(vec2 a) { return clamp(a, 0.0, 1.0); }
vec3 saturate(vec3 a) { return clamp(a, 0.0, 1.0); }
vec4 saturate(vec4 a) { return clamp(a, 0.0, 1.0); }

float distance_squared(vec2 a, vec2 b) { a -= b; return dot(a, a); }
float distance_squared(vec3 a, vec3 b) { a -= b; return dot(a, a); }
float len_squared(vec3 a) { return dot(a, a); }

float inverse_distance(vec3 V) { return max( 1 / length(V), 1e-8); }

vec2 mip_ratio_interp(float mip) {
	float low_mip = floor(mip);
	return mix(mipRatio[int(low_mip)], mipRatio[int(low_mip + 1.0)], mip - low_mip);
}
/* ------- Fast Math ------- */

/* [Drobot2014a] Low Level Optimizations for GCN */
float fast_sqrt(float v)
{
	return intBitsToFloat(0x1fbd1df5 + (floatBitsToInt(v) >> 1));
}

vec2 fast_sqrt(vec2 v)
{
	return intBitsToFloat(0x1fbd1df5 + (floatBitsToInt(v) >> 1));
}

/* [Eberly2014] GPGPU Programming for Games and Science */
float fast_acos(float v)
{
	float res = -0.156583 * abs(v) + M_PI_2;
	res *= fast_sqrt(1.0 - abs(v));
	return (v >= 0) ? res : M_PI - res;
}

vec2 fast_acos(vec2 v)
{
	vec2 res = -0.156583 * abs(v) + M_PI_2;
	res *= fast_sqrt(1.0 - abs(v));
	v.x = (v.x >= 0) ? res.x : M_PI - res.x;
	v.y = (v.y >= 0) ? res.y : M_PI - res.y;
	return v;
}

float point_plane_projection_dist(vec3 lineorigin, vec3 planeorigin, vec3 planenormal)
{
	return dot(planenormal, planeorigin - lineorigin);
}

float line_plane_intersect_dist(vec3 lineorigin, vec3 linedirection, vec3 planeorigin, vec3 planenormal)
{
	return dot(planenormal, planeorigin - lineorigin) / dot(planenormal, linedirection);
}

float line_plane_intersect_dist(vec3 lineorigin, vec3 linedirection, vec4 plane)
{
	vec3 plane_co = plane.xyz * (-plane.w / len_squared(plane.xyz));
	vec3 h = lineorigin - plane_co;
	return -dot(plane.xyz, h) / dot(plane.xyz, linedirection);
}

vec3 line_plane_intersect(vec3 lineorigin, vec3 linedirection, vec3 planeorigin, vec3 planenormal)
{
	float dist = line_plane_intersect_dist(lineorigin, linedirection, planeorigin, planenormal);
	return lineorigin + linedirection * dist;
}

vec3 line_plane_intersect(vec3 lineorigin, vec3 linedirection, vec4 plane)
{
	float dist = line_plane_intersect_dist(lineorigin, linedirection, plane);
	return lineorigin + linedirection * dist;
}

float line_aligned_plane_intersect_dist(vec3 lineorigin, vec3 linedirection, vec3 planeorigin)
{
	/* aligned plane normal */
	vec3 L = planeorigin - lineorigin;
	float diskdist = length(L);
	vec3 planenormal = -normalize(L);
	return -diskdist / dot(planenormal, linedirection);
}

vec3 line_aligned_plane_intersect(vec3 lineorigin, vec3 linedirection, vec3 planeorigin)
{
	float dist = line_aligned_plane_intersect_dist(lineorigin, linedirection, planeorigin);
	if (dist < 0) {
		/* if intersection is behind we fake the intersection to be
		 * really far and (hopefully) not inside the radius of interest */
		dist = 1e16;
	}
	return lineorigin + linedirection * dist;
}

float line_unit_sphere_intersect_dist(vec3 lineorigin, vec3 linedirection)
{
	float a = dot(linedirection, linedirection);
	float b = dot(linedirection, lineorigin);
	float c = dot(lineorigin, lineorigin) - 1;

	float dist = 1e15;
	float determinant = b * b - a * c;
	if (determinant >= 0)
		dist = (sqrt(determinant) - b) / a;

	return dist;
}

float line_unit_box_intersect_dist(vec3 lineorigin, vec3 linedirection)
{
	/* https://seblagarde.wordpress.com/2012/09/29/image-based-lighting-approaches-and-parallax-corrected-cubemap/ */
	vec3 firstplane  = (vec3( 1.0) - lineorigin) / linedirection;
	vec3 secondplane = (vec3(-1.0) - lineorigin) / linedirection;
	vec3 furthestplane = max(firstplane, secondplane);

	return min_v3(furthestplane);
}


/* Return texture coordinates to sample Surface LUT */
vec2 lut_coords(float cosTheta, float roughness)
{
	float theta = acos(cosTheta);
	vec2 coords = vec2(roughness, theta / M_PI_2);

	/* scale and bias coordinates, for correct filtered lookup */
	return coords * (LUT_SIZE - 1.0) / LUT_SIZE + 0.5 / LUT_SIZE;
}

/* -- Tangent Space conversion -- */
vec3 tangent_to_world(vec3 vector, vec3 N, vec3 T, vec3 B)
{
	return T * vector.x + B * vector.y + N * vector.z;
}

vec3 world_to_tangent(vec3 vector, vec3 N, vec3 T, vec3 B)
{
	return vec3( dot(T, vector), dot(B, vector), dot(N, vector));
}

void make_orthonormal_basis(vec3 N, out vec3 T, out vec3 B)
{
	vec3 UpVector = abs(N.z) < 0.99999 ? vec3(0.0,0.0,1.0) : vec3(1.0,0.0,0.0);
	T = normalize( cross(UpVector, N) );
	B = cross(N, T);
}

/* ---- Opengl Depth conversion ---- */

float linear_depth(bool is_persp, float z, float zf, float zn)
{
	if (is_persp) {
		return (zn  * zf) / (z * (zn - zf) + zf);
	}
	else {
		return (z * 2.0 - 1.0) * zf;
	}
}

float buffer_depth(bool is_persp, float z, float zf, float zn)
{
	if (is_persp) {
		return (zf * (zn - z)) / (z * (zn - zf));
	}
	else {
		return (z / (zf * 2.0)) + 0.5;
	}
}

float get_view_z_from_depth(float depth)
{
	if (ProjectionMatrix[3][3] == 0.0) {
		float d = 2.0 * depth - 1.0;
		return -ProjectionMatrix[3][2] / (d + ProjectionMatrix[2][2]);
	}
	else {
		return viewVecs[0].z + depth * viewVecs[1].z;
	}
}

float get_depth_from_view_z(float z)
{
	if (ProjectionMatrix[3][3] == 0.0) {
		float d = (-ProjectionMatrix[3][2] / z) - ProjectionMatrix[2][2];
		return d * 0.5 + 0.5;
	}
	else {
		return (z - viewVecs[0].z) / viewVecs[1].z;
	}
}

vec2 get_uvs_from_view(vec3 view)
{
	vec3 ndc = project_point(ProjectionMatrix, view);
	return ndc.xy * 0.5 + 0.5;
}

vec3 get_view_space_from_depth(vec2 uvcoords, float depth)
{
	if (ProjectionMatrix[3][3] == 0.0) {
		return vec3(viewVecs[0].xy + uvcoords * viewVecs[1].xy, 1.0) * get_view_z_from_depth(depth);
	}
	else {
		return viewVecs[0].xyz + vec3(uvcoords, depth) * viewVecs[1].xyz;
	}
}

vec3 get_world_space_from_depth(vec2 uvcoords, float depth)
{
	return (ViewMatrixInverse * vec4(get_view_space_from_depth(uvcoords, depth), 1.0)).xyz;
}

vec3 get_specular_reflection_dominant_dir(vec3 N, vec3 V, float roughness)
{
	vec3 R = -reflect(V, N);
	float smoothness = 1.0 - roughness;
	float fac = smoothness * (sqrt(smoothness) + roughness);
	return normalize(mix(N, R, fac));
}

float specular_occlusion(float NV, float AO, float roughness)
{
	return saturate(pow(NV + AO, roughness) - 1.0 + AO);
}

/* --- Refraction utils --- */

float ior_from_f0(float f0)
{
	float f = sqrt(f0);
	return (-f - 1.0) / (f - 1.0);
}

float f0_from_ior(float eta)
{
	float A = (eta - 1.0) / (eta + 1.0);
	return A * A;
}

vec3 get_specular_refraction_dominant_dir(vec3 N, vec3 V, float roughness, float ior)
{
	/* TODO: This a bad approximation. Better approximation should fit
	 * the refracted vector and roughness into the best prefiltered reflection
	 * lobe. */
	/* Correct the IOR for ior < 1.0 to not see the abrupt delimitation or the TIR */
	ior = (ior < 1.0) ? mix(ior, 1.0, roughness) : ior;
	float eta = 1.0 / ior;

	float NV = dot(N, -V);

	/* Custom Refraction. */
	float k = 1.0 - eta * eta * (1.0 - NV * NV);
	k = max(0.0, k); /* Only this changes. */
	vec3 R = eta * -V - (eta * NV + sqrt(k)) * N;

	return R;
}

float get_btdf_lut(sampler2DArray btdf_lut_tex, float NV, float roughness, float ior)
{
	const vec3 lut_scale_bias_texel_size = vec3((LUT_SIZE - 1.0), 0.5, 1.5) / LUT_SIZE;

	vec3 coords;
	/* Try to compensate for the low resolution and interpolation error. */
	coords.x = (ior > 1.0)
	           ? (0.9 + lut_scale_bias_texel_size.z) + (0.1 - lut_scale_bias_texel_size.z) * f0_from_ior(ior)
	           : (0.9 + lut_scale_bias_texel_size.z) * ior * ior;
	coords.y = 1.0 - saturate(NV);
	coords.xy *= lut_scale_bias_texel_size.x;
	coords.xy += lut_scale_bias_texel_size.y;

	const float lut_lvl_ofs = 4.0; /* First texture lvl of roughness. */
	const float lut_lvl_scale = 16.0; /* How many lvl of roughness in the lut. */

	float mip = roughness * lut_lvl_scale;
	float mip_floor = floor(mip);

	coords.z = lut_lvl_ofs + mip_floor + 1.0;
	float btdf_high = textureLod(btdf_lut_tex, coords, 0.0).r;

	coords.z -= 1.0;
	float btdf_low = textureLod(btdf_lut_tex, coords, 0.0).r;

	float btdf = (ior == 1.0) ? 1.0 : mix(btdf_low, btdf_high, mip - coords.z);

	return btdf;
}

/* ---- Encode / Decode Normal buffer data ---- */
/* From http://aras-p.info/texts/CompactNormalStorage.html
 * Using Method #4: Spheremap Transform */
vec2 normal_encode(vec3 n, vec3 view)
{
	float p = sqrt(n.z * 8.0 + 8.0);
	return n.xy / p + 0.5;
}

vec3 normal_decode(vec2 enc, vec3 view)
{
	vec2 fenc = enc * 4.0 - 2.0;
	float f = dot(fenc, fenc);
	float g = sqrt(1.0 - f / 4.0);
	vec3 n;
	n.xy = fenc*g;
	n.z = 1 - f / 2;
	return n;
}

/* ---- RGBM (shared multiplier) encoding ---- */
/* From http://iwasbeingirony.blogspot.fr/2010/06/difference-between-rgbm-and-rgbd.html */

/* Higher RGBM_MAX_RANGE gives imprecision issues in low intensity. */
#define RGBM_MAX_RANGE 512.0

vec4 rgbm_encode(vec3 rgb)
{
	float maxRGB = max_v3(rgb);
	float M = maxRGB / RGBM_MAX_RANGE;
	M = ceil(M * 255.0) / 255.0;
	return vec4(rgb / (M * RGBM_MAX_RANGE), M);
}

vec3 rgbm_decode(vec4 data)
{
	return data.rgb * (data.a * RGBM_MAX_RANGE);
}

/* ---- RGBE (shared exponent) encoding ---- */
vec4 rgbe_encode(vec3 rgb)
{
	float maxRGB = max_v3(rgb);
	float fexp = ceil(log2(maxRGB));
	return vec4(rgb / exp2(fexp), (fexp + 128.0) / 255.0);
}

vec3 rgbe_decode(vec4 data)
{
	float fexp = data.a * 255.0 - 128.0;
	return data.rgb * exp2(fexp);
}

#if 1
#define irradiance_encode rgbe_encode
#define irradiance_decode rgbe_decode
#else /* No ecoding (when using floating point format) */
#define irradiance_encode(X) (X).rgbb
#define irradiance_decode(X) (X).rgb
#endif

/* Irradiance Visibility Encoding */
#if 1
vec4 visibility_encode(vec2 accum, float range)
{
	accum /= range;

	vec4 data;
	data.x = fract(accum.x);
	data.y = floor(accum.x) / 255.0;
	data.z = fract(accum.y);
	data.w = floor(accum.y) / 255.0;

	return data;
}

vec2 visibility_decode(vec4 data, float range)
{
	return (data.xz + data.yw * 255.0) * range;
}
#else /* No ecoding (when using floating point format) */
vec4 visibility_encode(vec2 accum, float range)
{
	return accum.xyxy;
}

vec2 visibility_decode(vec4 data, float range)
{
	return data.xy;
}
#endif

/* Fresnel monochromatic, perfect mirror */
float F_eta(float eta, float cos_theta)
{
	/* compute fresnel reflectance without explicitly computing
	 * the refracted direction */
	float c = abs(cos_theta);
	float g = eta * eta - 1.0 + c * c;
	float result;

	if (g > 0.0) {
		g = sqrt(g);
		vec2 g_c = vec2(g) + vec2(c, -c);
		float A = g_c.y / g_c.x;
		A *= A;
		g_c *= c;
		float B = (g_c.y - 1.0) / (g_c.x + 1.0);
		B *= B;
		result = 0.5 * A * (1.0 + B);
	}
	else {
		result = 1.0;  /* TIR (no refracted component) */
	}

	return result;
}

/* Fresnel */
vec3 F_schlick(vec3 f0, float cos_theta)
{
	float fac = 1.0 - cos_theta;
	float fac2 = fac * fac;
	fac = fac2 * fac2 * fac;

	/* Unreal specular matching : if specular color is below 2% intensity,
	 * (using green channel for intensity) treat as shadowning */
	return saturate(50.0 * dot(f0, vec3(0.3, 0.6, 0.1))) * fac + (1.0 - fac) * f0;
}

/* Fresnel approximation for LTC area lights (not MRP) */
vec3 F_area(vec3 f0, vec2 lut)
{
	vec2 fac = normalize(lut.xy); /* XXX FIXME this does not work!!! */

	/* Unreal specular matching : if specular color is below 2% intensity,
	 * treat as shadowning */
	return saturate(50.0 * dot(f0, vec3(0.3, 0.6, 0.1))) * fac.y + fac.x * f0;
}

/* Fresnel approximation for IBL */
vec3 F_ibl(vec3 f0, vec2 lut)
{
	/* Unreal specular matching : if specular color is below 2% intensity,
	 * treat as shadowning */
	return saturate(50.0 * dot(f0, vec3(0.3, 0.6, 0.1))) * lut.y + lut.x * f0;
}

/* GGX */
float D_ggx_opti(float NH, float a2)
{
	float tmp = (NH * a2 - NH) * NH + 1.0;
	return M_PI * tmp*tmp; /* Doing RCP and mul a2 at the end */
}

float G1_Smith_GGX(float NX, float a2)
{
	/* Using Brian Karis approach and refactoring by NX/NX
	 * this way the (2*NL)*(2*NV) in G = G1(V) * G1(L) gets canceled by the brdf denominator 4*NL*NV
	 * Rcp is done on the whole G later
	 * Note that this is not convenient for the transmition formula */
	return NX + sqrt(NX * (NX - NX * a2) + a2);
	/* return 2 / (1 + sqrt(1 + a2 * (1 - NX*NX) / (NX*NX) ) ); /* Reference function */
}

float bsdf_ggx(vec3 N, vec3 L, vec3 V, float roughness)
{
	float a = roughness;
	float a2 = a * a;

	vec3 H = normalize(L + V);
	float NH = max(dot(N, H), 1e-8);
	float NL = max(dot(N, L), 1e-8);
	float NV = max(dot(N, V), 1e-8);

	float G = G1_Smith_GGX(NV, a2) * G1_Smith_GGX(NL, a2); /* Doing RCP at the end */
	float D = D_ggx_opti(NH, a2);

	/* Denominator is canceled by G1_Smith */
	/* bsdf = D * G / (4.0 * NL * NV); /* Reference function */
	return NL * a2 / (D * G); /* NL to Fit cycles Equation : line. 345 in bsdf_microfacet.h */
}

void accumulate_light(vec3 light, float fac, inout vec4 accum)
{
	accum += vec4(light, 1.0) * min(fac, (1.0 - accum.a));
}

/* ----------- Cone Apperture Approximation --------- */

/* Return a fitted cone angle given the input roughness */
float cone_cosine(float r)
{
	/* Using phong gloss
	 * roughness = sqrt(2/(gloss+2)) */
	float gloss = -2 + 2 / (r * r);
	/* Drobot 2014 in GPUPro5 */
	// return cos(2.0 * sqrt(2.0 / (gloss + 2)));
	/* Uludag 2014 in GPUPro5 */
	// return pow(0.244, 1 / (gloss + 1));
	/* Jimenez 2016 in Practical Realtime Strategies for Accurate Indirect Occlusion*/
	return exp2(-3.32193 * r * r);
}

/* --------- Closure ---------- */
#ifdef VOLUMETRICS

struct Closure {
	vec3 absorption;
	vec3 scatter;
	vec3 emission;
	float anisotropy;
};

#define CLOSURE_DEFAULT Closure(vec3(0.0), vec3(0.0), vec3(0.0), 0.0)

Closure closure_mix(Closure cl1, Closure cl2, float fac)
{
	Closure cl;
	cl.absorption = mix(cl1.absorption, cl2.absorption, fac);
	cl.scatter = mix(cl1.scatter, cl2.scatter, fac);
	cl.emission = mix(cl1.emission, cl2.emission, fac);
	cl.anisotropy = mix(cl1.anisotropy, cl2.anisotropy, fac);
	return cl;
}

Closure closure_add(Closure cl1, Closure cl2)
{
	Closure cl;
	cl.absorption = cl1.absorption + cl2.absorption;
	cl.scatter = cl1.scatter + cl2.scatter;
	cl.emission = cl1.emission + cl2.emission;
	cl.anisotropy = (cl1.anisotropy + cl2.anisotropy) / 2.0; /* Average phase (no multi lobe) */
	return cl;
}

#else /* VOLUMETRICS */

struct Closure {
	vec3 radiance;
	float opacity;
#  ifdef USE_SSS
	vec4 sss_data;
#    ifdef USE_SSS_ALBEDO
	vec3 sss_albedo;
#    endif
#  endif
	vec4 ssr_data;
	vec2 ssr_normal;
	int ssr_id;
};

/* This is hacking ssr_id to tag transparent bsdf */
#define TRANSPARENT_CLOSURE_FLAG -2
#define REFRACT_CLOSURE_FLAG -3

#  ifdef USE_SSS
#    ifdef USE_SSS_ALBEDO
#define CLOSURE_DEFAULT Closure(vec3(0.0), 1.0, vec4(0.0), vec3(0.0), vec4(0.0), vec2(0.0), -1)
#    else
#define CLOSURE_DEFAULT Closure(vec3(0.0), 1.0, vec4(0.0), vec4(0.0), vec2(0.0), -1)
#    endif
#  else
#define CLOSURE_DEFAULT Closure(vec3(0.0), 1.0, vec4(0.0), vec2(0.0), -1)
#  endif

uniform int outputSsrId;

Closure closure_mix(Closure cl1, Closure cl2, float fac)
{
	Closure cl;

	if (cl1.ssr_id == TRANSPARENT_CLOSURE_FLAG) {
		cl1.radiance = cl2.radiance;
		cl1.ssr_normal = cl2.ssr_normal;
		cl1.ssr_data = cl2.ssr_data;
		cl1.ssr_id = cl2.ssr_id;
#  ifdef USE_SSS
		cl1.sss_data = cl2.sss_data;
#    ifdef USE_SSS_ALBEDO
		cl1.sss_albedo = cl2.sss_albedo;
#    endif
#  endif
	}
	if (cl2.ssr_id == TRANSPARENT_CLOSURE_FLAG) {
		cl2.radiance = cl1.radiance;
		cl2.ssr_normal = cl1.ssr_normal;
		cl2.ssr_data = cl1.ssr_data;
		cl2.ssr_id = cl1.ssr_id;
#  ifdef USE_SSS
		cl2.sss_data = cl1.sss_data;
#    ifdef USE_SSS_ALBEDO
		cl2.sss_albedo = cl1.sss_albedo;
#    endif
#  endif
	}
	if (cl1.ssr_id == outputSsrId) {
		cl.ssr_data = mix(cl1.ssr_data.xyzw, vec4(vec3(0.0), cl1.ssr_data.w), fac); /* do not blend roughness */
		cl.ssr_normal = cl1.ssr_normal;
		cl.ssr_id = cl1.ssr_id;
	}
	else {
		cl.ssr_data = mix(vec4(vec3(0.0), cl2.ssr_data.w), cl2.ssr_data.xyzw, fac); /* do not blend roughness */
		cl.ssr_normal = cl2.ssr_normal;
		cl.ssr_id = cl2.ssr_id;
	}
	cl.radiance = mix(cl1.radiance, cl2.radiance, fac);
	cl.opacity = mix(cl1.opacity, cl2.opacity, fac);

#  ifdef USE_SSS
	cl.sss_data.rgb = mix(cl1.sss_data.rgb, cl2.sss_data.rgb, fac);
	cl.sss_data.a = (cl1.sss_data.a > 0.0) ? cl1.sss_data.a : cl2.sss_data.a;
#    ifdef USE_SSS_ALBEDO
	/* TODO Find a solution to this. Dither? */
	cl.sss_albedo = (cl1.sss_data.a > 0.0) ? cl1.sss_albedo : cl2.sss_albedo;
#    endif
#  endif

	return cl;
}

Closure closure_add(Closure cl1, Closure cl2)
{
	Closure cl = (cl1.ssr_id == outputSsrId) ? cl1 : cl2;
#  ifdef USE_SSS
	cl.sss_data = (cl1.sss_data.a > 0.0) ? cl1.sss_data : cl2.sss_data;
#    ifdef USE_SSS_ALBEDO
	/* TODO Find a solution to this. Dither? */
	cl.sss_albedo = (cl1.sss_data.a > 0.0) ? cl1.sss_albedo : cl2.sss_albedo;
#    endif
#  endif
	cl.radiance = cl1.radiance + cl2.radiance;
	cl.opacity = saturate(cl1.opacity + cl2.opacity);
	return cl;
}

#  if defined(MESH_SHADER) && !defined(USE_ALPHA_HASH) && !defined(USE_ALPHA_CLIP) && !defined(SHADOW_SHADER) && !defined(USE_MULTIPLY)
layout(location = 0) out vec4 fragColor;
layout(location = 1) out vec4 ssrNormals;
layout(location = 2) out vec4 ssrData;
#    ifdef USE_SSS
layout(location = 3) out vec4 sssData;
#      ifdef USE_SSS_ALBEDO
layout(location = 4) out vec4 sssAlbedo;
#      endif /* USE_SSS_ALBEDO */
#    endif /* USE_SSS */

Closure nodetree_exec(void); /* Prototype */

#    if defined(USE_ALPHA_BLEND_VOLUMETRICS)
/* Prototype because this file is included before volumetric_lib.glsl */
vec4 volumetric_resolve(vec4 scene_color, vec2 frag_uvs, float frag_depth);
#    endif

#define NODETREE_EXEC
void main()
{
	Closure cl = nodetree_exec();
#    ifndef USE_ALPHA_BLEND
	/* Prevent alpha hash material writing into alpha channel. */
	cl.opacity = 1.0;
#    endif

#    if defined(USE_ALPHA_BLEND_VOLUMETRICS)
	/* XXX fragile, better use real viewport resolution */
	vec2 uvs = gl_FragCoord.xy / vec2(2 * textureSize(maxzBuffer, 0).xy);
	fragColor = volumetric_resolve(vec4(cl.radiance, cl.opacity), uvs, gl_FragCoord.z);
#    else
	fragColor = vec4(cl.radiance, cl.opacity);
#    endif

	ssrNormals = cl.ssr_normal.xyyy;
	ssrData = cl.ssr_data;
#    ifdef USE_SSS
	sssData = cl.sss_data;
#      ifdef USE_SSS_ALBEDO
	sssAlbedo = cl.sss_albedo.rgbb;
#      endif
#    endif

	/* For Probe capture */
#    ifdef USE_SSS
#      ifdef USE_SSS_ALBEDO
	fragColor.rgb += cl.sss_data.rgb * cl.sss_albedo.rgb * float(!sssToggle);
#      else
	fragColor.rgb += cl.sss_data.rgb * float(!sssToggle);
#      endif
#    endif
}

#  endif /* MESH_SHADER && !SHADOW_SHADER */

#endif /* VOLUMETRICS */

Closure nodetree_exec(void); /* Prototype */

/* TODO find a better place */
#ifdef USE_MULTIPLY

out vec4 fragColor;

#define NODETREE_EXEC
void main()
{
	Closure cl = nodetree_exec();
	fragColor = vec4(mix(vec3(1.0), cl.radiance, cl.opacity), 1.0);
}
#endif