//
// Copyright (C) 2012 Jorge Jimenez (jorge@iryoku.com)
// Copyright (C) 2012 Diego Gutierrez (diegog@unizar.es)
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
// 
//    1. Redistributions of source code must retain the above copyright notice,
//       this list of conditions and the following disclaimer.
//
//    2. Redistributions in binary form must reproduce the following disclaimer
//       in the documentation and/or other materials provided with the 
//       distribution:
//
//       "Uses Separable SSS. Copyright (C) 2012 by Jorge Jimenez and Diego
//        Gutierrez."
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS 
// IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, 
// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 
// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDERS OR CONTRIBUTORS 
// BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
// POSSIBILITY OF SUCH DAMAGE.
//
// The views and conclusions contained in the software and documentation are 
// those of the authors and should not be interpreted as representing official
// policies, either expressed or implied, of the copyright holders.
//

#version 450

#include "compiled.inc"
#include "std/gbuffer.glsl"

uniform sampler2D gbufferD;
uniform sampler2D gbuffer0;
uniform sampler2D gbuffer1;
uniform sampler2D tex;

uniform vec2 dir;
uniform vec2 cameraProj;
uniform mat4 projectionMatrix;

#ifdef _ExtBRDF
//!uniform vec4 materialParams[MAX_MATERIALS * 8];
#endif

in vec2 texCoord;
out vec4 fragColor;

// TODO: finish the SSS
const float SSS_SCALE = 0.05;
const float DEPTH_THRESHOLD = 0.05;

float hash13(vec3 p3) {
	p3 = fract(p3 * vec3(0.1031, 0.1030, 0.0973));
	p3 += dot(p3, p3.yzx + 33.33);
	return fract((p3.x + p3.y) * p3.z);
}

vec4 SSSSBlur(vec3 sssRadius, float sssWeight) {
	const int SSSS_N_SAMPLES = 11;
	vec4 kernel[SSSS_N_SAMPLES];

	kernel[0] = vec4(0.233, 0.455, 0.649, 0.0);     // Center sample
	kernel[1] = vec4(0.100, 0.336, 0.344, 0.37);    // +0.37
	kernel[2] = vec4(0.118, 0.198, 0.0,   0.97);    // +0.97
	kernel[3] = vec4(0.113, 0.007, 0.007, 1.93);    // +1.93
	kernel[4] = vec4(0.358, 0.004, 0.0,   3.87);    // +3.87
	kernel[5] = vec4(0.078, 0.0,   0.0,   6.53);    // +6.53 (red only)
	kernel[6] = vec4(0.100, 0.336, 0.344, -0.37);   // -0.37
	kernel[7] = vec4(0.118, 0.198, 0.0,   -0.97);   // -0.97
	kernel[8] = vec4(0.113, 0.007, 0.007, -1.93);   // -1.93
	kernel[9] = vec4(0.358, 0.004, 0.0,   -3.87);   // -3.87
	kernel[10] = vec4(0.078, 0.0,   0.0,   -6.53);  // -6.53 (red only)

	vec2 texSize = vec2(textureSize(tex, 0));
	ivec2 texelCoord = ivec2(texCoord * texSize);

	vec4 colorM = texelFetch(tex, texelCoord, 0);
	vec3 albedo = texelFetch(gbuffer1, texelCoord, 0).rgb;

	vec3 irradianceM = colorM.rgb / max(albedo, vec3(0.00001));

	float depth = texelFetch(gbufferD, texelCoord, 0).r;
	float depthM = cameraProj.y / (depth - cameraProj.x);

	float blurWidth = max(max(sssRadius.r, sssRadius.g), sssRadius.b);
	float projScale = dot(dir, vec2(projectionMatrix[0][0], projectionMatrix[1][1]));
	vec2 finalStep = blurWidth * (1.0 / depthM) * dir * projScale * SSS_SCALE;

	vec3 jitterSeed = vec3(texCoord.xy * 1000.0, fract(cameraProj.x * 0.0001));
	float jitterOffset = (hash13(jitterSeed) * 2.0 - 1.0) * 0.15;
	finalStep *= (1.0 + jitterOffset);

	vec3 colorBlurred = irradianceM * kernel[0].rgb;
	vec3 weightSum = kernel[0].rgb;

	for (int i = 1; i < SSSS_N_SAMPLES; i++) {
		float sampleJitter = hash13(vec3(texCoord.xy * 720.0, float(i) * 37.45)) * 0.1 - 0.05;
		vec2 offset = texCoord + (kernel[i].a + sampleJitter) * finalStep;

		vec3 irradiance = irradianceM;
		float s = 0.0;
		if (all(greaterThanEqual(offset, vec2(0.0))) && all(lessThan(offset, vec2(1.0)))) {
			ivec2 sampleTexel = ivec2(offset * texSize);

			float sampleDepth = texelFetch(gbufferD, sampleTexel, 0).r;
			float sampleDepthM = cameraProj.y / (sampleDepth - cameraProj.x);
			float depthDiff = abs(depthM - sampleDepthM);

			if (depthDiff < 1.0) {
				vec4 sampleG0 = texelFetch(gbuffer0, sampleTexel, 0);
				float sampleMetallic;
				uint sampleMatid;
				unpackFloatInt16(sampleG0.a, sampleMetallic, sampleMatid);
				bool sampleIsSSS = false;
				#ifdef _ExtBRDF
				if (sampleMatid >= 3u && sampleMatid < uint(MAX_MATERIALS)) {
					if (materialParams[sampleMatid * 8u + 3u].z > 0.0) sampleIsSSS = true;
				}
				#endif

				if (sampleIsSSS) {
					vec3 sampleColor = texelFetch(tex, sampleTexel, 0).rgb;
					vec3 sampleAlbedo = texelFetch(gbuffer1, sampleTexel, 0).rgb;
					irradiance = sampleColor / max(sampleAlbedo, vec3(0.00001));
				}

				if (depthDiff <= DEPTH_THRESHOLD) {
					s = 1.0;
				} else {
					s = exp(-depthDiff * 10.0);
				}
			}
		}

		colorBlurred += kernel[i].rgb * mix(irradianceM, irradiance, s);
		weightSum += kernel[i].rgb;
	}

	vec3 normalizedIrradiance = colorBlurred / max(weightSum, vec3(0.00001));
	float dither = hash13(vec3(texCoord * 1333.0, 0.0)) * 0.003 - 0.0015;
	normalizedIrradiance = max(normalizedIrradiance + vec3(dither), vec3(0.0));
	vec3 blurredColor = normalizedIrradiance * albedo;
	vec3 result = mix(colorM.rgb, blurredColor, sssWeight);
	return vec4(result, colorM.a);
}

void main() {
	vec2 texSize0 = vec2(textureSize(gbuffer0, 0));
	ivec2 texelCoord0 = ivec2(texCoord * texSize0);
	vec4 g0 = texelFetch(gbuffer0, texelCoord0, 0);
	float metallic;
	uint matid;
	unpackFloatInt16(g0.a, metallic, matid);
	
	bool applySSS = false;
	vec3 sssRadius = vec3(1.0);
	float sssWeight = 1.0;
	vec4 matp0, matp1, matp2, matp3, matp4, matp5, matp6, matp7;
	#ifdef _ExtBRDF
	if (matid >= 3u && matid < uint(MAX_MATERIALS)) {
		getMaterialParams(matid, matp0, matp1, matp2, matp3, matp4, matp5, matp6, matp7);
		// matp3.z = subsurface, matp4.xyz = subsurfaceRadiusRGB, matp7.x = subsurfaceScale
		if (matp3.z > 0.0) {
			applySSS = true;
			sssRadius = matp4.xyz * matp7.x;
			sssWeight = matp3.z;
		}
	}
	#endif

	if (applySSS) {
		fragColor = SSSSBlur(sssRadius, sssWeight);
	} else {
		vec2 texSizeMain = vec2(textureSize(tex, 0));
		ivec2 texelCoordMain = ivec2(texCoord * texSizeMain);
		fragColor = texelFetch(tex, texelCoordMain, 0);
	}
}