//
// 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 tex;

uniform vec2 dir;
uniform vec2 cameraProj;

in vec2 texCoord;
out vec4 fragColor;

const vec3 SKIN_SSS_RADIUS = vec3(4.8, 2.4, 1.5);
const float SSS_DISTANCE_SCALE = 0.001;

// Temp hash func - 
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() {
	const int SSSS_N_SAMPLES = 15;
	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);    // +0.37mm
	kernel[2] = vec4(0.118, 0.198, 0.0,   0.97);    // +0.97mm
	kernel[3] = vec4(0.113, 0.007, 0.007, 1.93);    // +1.93mm
	kernel[4] = vec4(0.358, 0.004, 0.0,   3.87);    // +3.87mm
	kernel[5] = vec4(0.078, 0.0,   0.0,   6.53);    // +6.53mm (red only)
	kernel[6] = vec4(0.0,   0.0,   0.0,   0.0);     // Unused
	kernel[7] = vec4(0.0,   0.0,   0.0,   0.0);     // Unused
	kernel[8] = vec4(0.100, 0.336, 0.344, -0.37);   // -0.37mm
	kernel[9] = vec4(0.118, 0.198, 0.0,   -0.97);   // -0.97mm
	kernel[10] = vec4(0.113, 0.007, 0.007, -1.93);  // -1.93mm
	kernel[11] = vec4(0.358, 0.004, 0.0,   -3.87);  // -3.87mm
	kernel[12] = vec4(0.078, 0.0,   0.0,   -6.53);  // -6.53mm (red only)
	kernel[13] = vec4(0.0,   0.0,   0.0,   0.0);    // Unused
	kernel[14] = vec4(0.0,   0.0,   0.0,   0.0);    // Unused
	
	vec4 colorM = textureLod(tex, texCoord, 0.0);

	float depth = textureLod(gbufferD, texCoord, 0.0).r;
	float depthM = cameraProj.y / (depth - cameraProj.x);

	float distanceScale = 1.0 / max(depthM, 0.1);
	
	vec2 finalStep = sssWidth * distanceScale * dir * SSS_DISTANCE_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 = vec3(0.0);
	vec3 weightSum = vec3(0.0);
	colorBlurred += colorM.rgb * kernel[0].rgb;
	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;
		vec4 color = textureLod(tex, offset, 0.0);
		const float DEPTH_THRESHOLD = 0.05;
		float sampleDepth = textureLod(gbufferD, offset, 0.0).r;
		float sampleDepthM = cameraProj.y / (sampleDepth - cameraProj.x);
		
		float depthDiff = abs(depthM - sampleDepthM);
		float depthWeight = exp(-depthDiff * 10.0);
		
		if (depthDiff > DEPTH_THRESHOLD) {
			color.rgb = mix(colorM.rgb, color.rgb, depthWeight);
		}
		
		colorBlurred += color.rgb * kernel[i].rgb;
		weightSum += kernel[i].rgb;
	}
	vec3 normalizedColor = colorBlurred / max(weightSum, vec3(0.00001));
	float dither = hash13(vec3(texCoord * 1333.0, 0.0)) * 0.003 - 0.0015;
	normalizedColor = max(normalizedColor + vec3(dither), vec3(0.0));
	return vec4(normalizedColor, colorM.a);
}

void main() {
	vec4 g0 = textureLod(gbuffer0, texCoord, 0.0);
	float metallic;
	uint matid;
	unpackFloatInt16(g0.a, metallic, matid);
	
	if (matid == 2u) {
		vec4 originalColor = textureLod(tex, texCoord, 0.0);
		vec4 blurredColor = SSSSBlur();
		vec4 sssContribution = blurredColor - originalColor;
		vec4 combined = originalColor + max(vec4(0.0), sssContribution) * 0.8;
		fragColor = max(vec4(0.0), min(combined, vec4(10.0)));
	} else {
		fragColor = textureLod(tex, texCoord, 0.0);
	}
}