#line 2
/**
 * @file        ssao.frag
 *
 * @author      FH Wedel, Henrik Patjens
 * @date        November 2017
 * @brief       Fragment-Shader zum Rendern von Objekten mit Forward-Rendering
 *
 * Diese Datei ist Bestandteil des Praktikums "Special Effects und Shaderprogrammierung".
 *
 * Copyright (C) 2017 by FH Wedel
 */


#define DIST_MIN 0.0001
#define DIST_MAX 0.005


// Version wird durch die utils.glsl definiert.
out vec4 FragColor;                         /**< Farbe des Fragments */

// ----------------------------------------------------------------------------
//
// Uniforms
//
// ----------------------------------------------------------------------------
layout (binding = 0) uniform sampler2D normalTex;
layout (binding = 1) uniform sampler2D depthTex;
//layout (RGBA8, binding = 2) uniform image2D discardTex;
uniform int sampleSize;
uniform mat4 ProjectionMatrix;
uniform mat4 InverseProjectionMatrix;
uniform int resX;
uniform int resY;

// ----------------------------------------------------------------------------
//
// Variablen
//
// ----------------------------------------------------------------------------

// ----------------------------------------------------------------------------
//
// Funktionen
//
// ----------------------------------------------------------------------------

/**
* Berechnet die View Space position des aktuellen Fragments
*/
vec3 getViewPos(){
    float x = (gl_FragCoord.x / resX) * 2.0 - 1.0;
    float y = (gl_FragCoord.y / resY) * 2.0 - 1.0;
    float z = texture(depthTex, gl_FragCoord.xy).r * 2.0 - 1.0;
    vec4 projPos = vec4(x,y,z, 1.0);
    vec4 viewPos = InverseProjectionMatrix * projPos;
    return wdiv(viewPos);
}

/**
 * Einsprungpunkt für den Fragment-Shader
 */
void main() {
    float occlusion = 0.0;

    vec3 origin = getViewPos();

    vec3 normal = normalize(texture(normalTex,gl_FragCoord.xy).rgb * 2.0 - 1.0);
    //vec3 normal = normalize(texelFetch(normalTex, ivec2(gl_FragCoord.xy),0).xyz * 2.0 - 1.0);
    vec3 u = normalize(vec3(rand(gl_FragCoord.xy),rand(gl_FragCoord.yz),rand(gl_FragCoord.xz)));
    //TODO: n == u beachten!
    vec3 tangent = normalize(cross(normal,u));
    vec3 bitangent = normalize(cross(normal, tangent));
    mat3 tbn = mat3(tangent, bitangent, normal);

    for(int i = 0; i < sampleSize; i++){
        //sample position berechnen
        vec3 kernel = tbn * sampleHemisphereCos(hammersley(i, sampleSize));
        kernel = kernel + origin;
        //projizieren
        vec4 offset = vec4(kernel,1.0);
        offset = ProjectionMatrix * offset;
        vec3 fOffset = wdiv(offset);
        fOffset.xy = fOffset.xy * 0.5 + 0.5; //scale & bias

        //sample tiefe berechnen
        float depth = texture(depthTex, fOffset.xy).r * 2.0 - 1.0;

        //float dist = fOffset.z - depth;

        if(fOffset.z > depth){
            occlusion += 1.0;
        } /**else {
            imageStore(discardTex, gl_FragCoord.xy, vec4(1,0,0,1));
        }*/

    }

    occlusion = 1.0 - (occlusion/sampleSize);
    FragColor = vec4(occlusion, 0.0, 0.0, 1.0);

}