// G BUFFER

uniform sampler2DRect positionBuffer;
// - Albedo + Roughness
uniform sampler2DRect albedoBuffer;
// - Normal buffer
uniform sampler2DRect normalBuffer;
// - Emission + Metallic
uniform sampler2DRect emissionBuffer;

// LIGHT BUFFER

uniform sampler2DRect lightBuffer;

// FOG PARAMETERS

uniform vec3 be;
uniform vec3 bi;
uniform vec3 fogColor;

// OUTPUT LIGHT

layout(location = 0)out vec4 outColor;

// FUNCTIONS

vec3 applyFog( in vec3 rgb,
               in float distance)
{
    vec3 extColor = vec3( exp(-distance*be.x), exp(-distance*be.y), exp(-distance*be.z) );
    vec3 insColor = vec3( exp(-distance*bi.x), exp(-distance*bi.y), exp(-distance*bi.z) );
    return rgb*extColor + fogColor*(1.0-insColor);
}

// MAIN PROGRAM

void main(void) {
    ivec2 texCoord = ivec2(gl_FragCoord.xy);
    vec3 color = texelFetch(lightBuffer, texCoord).xyz;

    // gbuffer variables
    /*
    vec3 ambientColor = texelFetch(emissionBuffer, texCoord).rgb;
    vec3 normal = texelFetch(normalBuffer, texCoord).xyz;
    vec4 albedoTexel = texelFetch(albedoBuffer, texCoord);
    vec3 albedo = albedoTexel.rgb;
    float roughness = albedoTexel.a;
    vec4 emissionTexel = texelFetch(emissionBuffer, texCoord);
    vec3 emission = emissionTexel.rgb;
    float metallic = emissionTexel.a;
    */
    vec4 fragPos = texelFetch(positionBuffer, texCoord);

    // fog
    color = applyFog(color, -fragPos.z);

    // HDR tonemapping
#ifdef HDR_TONEMAPPING
    color = color / (color + vec3(1.0));
#endif

    // gamma correct
#ifdef GAMMA_CORRECT
    color = pow(color, vec3(1.0/2.2));
#endif

    outColor = vec4(color, 1.0);
}