<@include gpu/Config.slh@>
<$VERSION_HEADER$>
//  Generated on <$_SCRIBE_DATE$>
//
//  subsurfaceScattering_drawScattering.frag
//
//  Created by Sam Gateau on 6/8/16.
//  Copyright 2016 High Fidelity, Inc.
//
//  Distributed under the Apache License, Version 2.0.
//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
//


<@include gpu/ShaderConstants.h@>

<@include DeferredBufferRead.slh@>
<@include graphics/Light.slh@>
<$declareLightBuffer()$>

<$declareDeferredCurvature()$>

<@include SubsurfaceScattering.slh@>
<$declareSubsurfaceScatteringBRDF()$>

layout(location=0) in vec2 varTexCoord0;
layout(location=0) out vec4 _fragColor;

struct SSSDebugParams {
    vec4 cursorTexCoordSpare2;
};

// Deferred frame transform uses slot 0
LAYOUT_STD140(binding=1) uniform sssDebugParamsBuffer {
    SSSDebugParams sssDebugParams;
};

vec3 evalScatteringBRDF(vec2 texcoord) {
    DeferredFragment fragment = unpackDeferredFragmentNoPosition(texcoord);

    vec3 normal = fragment.normal; // .getWorldNormal(varTexCoord0);
    vec4 blurredCurvature = fetchCurvature(texcoord);
    vec4 diffusedCurvature = fetchDiffusedCurvature(texcoord);
    vec3 midNormal = normalize((blurredCurvature.xyz - 0.5f) * 2.0f);
    vec3 lowNormal = normalize((diffusedCurvature.xyz - 0.5f) * 2.0f);
    float curvature = unpackCurvature(diffusedCurvature.w);


    // Transform directions to worldspace
    vec3 fragNormal = vec3((normal));

    // Get light
    Light light = getKeyLight();
    vec3 fresnel = vec3(0.028); // Default Di-electric fresnel value for skin
    float metallic = 0.0;

    vec3 fragLightDir = -normalize(getLightDirection(light));


    vec3 brdf = evalSkinBRDF(fragLightDir, fragNormal, midNormal, lowNormal, curvature);

    return brdf;
}

vec3 drawScatteringTableUV(vec2 cursor, vec2 texcoord) {
    DeferredFragment fragment = unpackDeferredFragmentNoPosition(cursor);

    vec3 normal = fragment.normal; // .getWorldNormal(varTexCoord0);
    vec4 blurredCurvature = fetchCurvature(cursor);
    vec4 diffusedCurvature = fetchDiffusedCurvature(cursor);
    vec3 midNormal = normalize((blurredCurvature.xyz - 0.5f) * 2.0f);
    vec3 lowNormal = normalize((diffusedCurvature.xyz - 0.5f) * 2.0f);
    float curvature = unpackCurvature(diffusedCurvature.w);

    // Get light
    Light light = getKeyLight();
    vec3 fresnel = vec3(0.028); // Default Di-electric fresnel value for skin

    vec3 fragLightDir = -normalize(getLightDirection(light));

    vec3 bentNdotL = evalScatteringBentNdotL(normal, midNormal, lowNormal, fragLightDir);

    vec3 distance = vec3(0.0);
    for (int c = 0; c < 3; c++) {
        vec2 BRDFuv = vec2(clamp(bentNdotL[c] * 0.5 + 0.5, 0.0, 1.0), clamp(2.0 * curvature, 0.0, 1.0));
        vec2 delta = BRDFuv - texcoord;
        distance[c] = 1.0 - dot(delta, delta);
    }

    distance *= distance;

    float threshold = 0.999;
    vec3 color = vec3(0.0);
    bool keep = false;
    for (int c = 0; c < 3; c++) {
        bool check = distance[c] > threshold;
        keep = keep || check;
        color[c] += float(check);
    }

    if (!keep) {
        discard;
    }

    return color;
}

void main(void) {
    vec2 cursorTexcoord = sssDebugParams.cursorTexCoordSpare2.xy;
    _fragColor = vec4(drawScatteringTableUV(cursorTexcoord, varTexCoord0), 1.0);
}