/**
 * 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

#ifdef GL_ES
precision mediump float;
#endif

#include "../compiled.glsl"

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

uniform vec2 dir;

in vec2 texCoord;
out vec4 fragColor;

const float SSSS_FOVY = 45.0;

// Separable SSS Reflectance
vec4 SSSSBlur(float sssWidth) {
	// Quality = 0
	const int SSSS_N_SAMPLES  = 11;
	vec4 kernel[SSSS_N_SAMPLES];		
	kernel[0] = vec4(0.560479, 0.669086, 0.784728, 0);
	kernel[1] = vec4(0.00471691, 0.000184771, 5.07566e-005, -2);
	kernel[2] = vec4(0.0192831, 0.00282018, 0.00084214, -1.28);
	kernel[3] = vec4(0.03639, 0.0130999, 0.00643685, -0.72);
	kernel[4] = vec4(0.0821904, 0.0358608, 0.0209261, -0.32);
	kernel[5] = vec4(0.0771802, 0.113491, 0.0793803, -0.08);
	kernel[6] = vec4(0.0771802, 0.113491, 0.0793803, 0.08);
	kernel[7] = vec4(0.0821904, 0.0358608, 0.0209261, 0.32);
	kernel[8] = vec4(0.03639, 0.0130999, 0.00643685, 0.72);
	kernel[9] = vec4(0.0192831, 0.00282018, 0.00084214, 1.28);
	kernel[10] = vec4(0.00471691, 0.000184771, 5.07565e-005, 2);
	
	vec4 colorM = texture(tex, texCoord);

	// Initialize the stencil buffer in case it was not already available:
	// if (initStencil) // (Checked in compile time, it's optimized away)
		// if (SSSS_STREGTH_SOURCE == 0.0) discard;

	// Fetch linear depth of current pixel
	// vec4 g0 = texture(gbuffer0, texCoord);
	// float depth = 1.0 - g0.a;
	float depth = texture(gbufferD, texCoord).r * 2.0 - 1.0;
	const float projectionA = cameraPlane.y / (cameraPlane.y - cameraPlane.x);
	const float projectionB = (-cameraPlane.y * cameraPlane.x) / (cameraPlane.y - cameraPlane.x);
	float depthM = projectionB / (depth * 0.5 + 0.5 - projectionA);

	// Calculate the sssWidth scale (1.0 for a unit plane sitting on the projection window)
	float distanceToProjectionWindow = 1.0 / tan(0.5 * radians(SSSS_FOVY));
	float scale = distanceToProjectionWindow / depthM;

	// Calculate the final step to fetch the surrounding pixels
	vec2 finalStep = sssWidth * scale * dir;
	finalStep *= 1.0;//SSSS_STREGTH_SOURCE; // Modulate it using the alpha channel.
	finalStep *= 1.0 / 3.0; // Divide by 3 as the kernels range from -3 to 3.

	// Accumulate the center sample:
	vec4 colorBlurred = colorM;
	colorBlurred.rgb *= kernel[0].rgb;

	// Accumulate the other samples
	// for (int i = 1; i < SSSS_N_SAMPLES; i++) {
		// Fetch color and depth for current sample
		vec2 offset = texCoord + kernel[1].a * finalStep;
		vec4 color = texture(tex, offset);
		// #if SSSS_FOLLOW_SURFACE == 1
		// If the difference in depth is huge, we lerp color back to "colorM":
		// float depth = texture(depthTex, offset).r;
		// float s = SSSSSaturate(300.0f * distanceToProjectionWindow *
							//    sssWidth * abs(depthM - depth));
		// color.rgb = SSSSLerp(color.rgb, colorM.rgb, s);
		// #endif
		// Accumulate
		colorBlurred.rgb += kernel[1].rgb * color.rgb;
		
		
		offset = texCoord + kernel[2].a * finalStep;
		color = texture(tex, offset);
		colorBlurred.rgb += kernel[2].rgb * color.rgb;
		
		offset = texCoord + kernel[3].a * finalStep;
		color = texture(tex, offset);
		colorBlurred.rgb += kernel[3].rgb * color.rgb;
		
		offset = texCoord + kernel[4].a * finalStep;
		color = texture(tex, offset);
		colorBlurred.rgb += kernel[4].rgb * color.rgb;
		
		offset = texCoord + kernel[5].a * finalStep;
		color = texture(tex, offset);
		colorBlurred.rgb += kernel[5].rgb * color.rgb;
		
		offset = texCoord + kernel[6].a * finalStep;
		color = texture(tex, offset);
		colorBlurred.rgb += kernel[6].rgb * color.rgb;
		
		offset = texCoord + kernel[7].a * finalStep;
		color = texture(tex, offset);
		colorBlurred.rgb += kernel[7].rgb * color.rgb;
		
		offset = texCoord + kernel[8].a * finalStep;
		color = texture(tex, offset);
		colorBlurred.rgb += kernel[8].rgb * color.rgb;
		
		offset = texCoord + kernel[9].a * finalStep;
		color = texture(tex, offset);
		colorBlurred.rgb += kernel[9].rgb * color.rgb;
		
		offset = texCoord + kernel[10].a * finalStep;
		color = texture(tex, offset);
		colorBlurred.rgb += kernel[10].rgb * color.rgb;
	// }

	return colorBlurred;
}

void main() {
	// SSS only masked objects
	if (texture(gbuffer0, texCoord).a == 2.0) {
		fragColor = SSSSBlur(0.005);
	}
	else {
		fragColor = texture(tex, texCoord);
	}
}