<!
//  DeferredLighting.slh
//  libraries/render-utils/src
//
//  Created by Sam Gateau on 1/15/15.
//  Copyright 2013 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
!>
<@if not DEFERRED_LIGHTING_SLH@>
<@def DEFERRED_LIGHTING_SLH@>


<@func declareEvalPBRShading()@>
// Frag Shading returns the diffuse amount as W and the specular rgb as xyz
vec4 evalPBRShading(vec3 fragNormal, vec3 fragLightDir, vec3 fragEyeDir, vec3 specular, float gloss) {
    // Diffuse Lighting
    float diffuseDot = dot(fragNormal, fragLightDir);
    float facingLight = step(0.0, diffuseDot);
    float diffuse = diffuseDot * facingLight;
 
    // Specular Lighting depends on the half vector and the gloss
    vec3 halfDir = normalize(fragEyeDir + fragLightDir);

   // float specularPower = pow(facingLight * max(0.0, dot(halfDir, fragNormal)), gloss * 128.0);
    float specularPower = pow(max(0.0, dot(halfDir, fragNormal)), gloss * 128.0);
    specularPower *= (gloss * 128.0 * 0.125 + 0.25);

    float shlickPower = (1.0 - dot(fragLightDir,halfDir));
    float shlickPower2 = shlickPower * shlickPower;
    float shlickPower5 = shlickPower2 * shlickPower2 * shlickPower;
    vec3 schlick = specular * (1.0 - shlickPower5) + vec3(shlickPower5);
    vec3 reflect = specularPower * schlick;

    // FIXME:
    //return vec4(reflect, diffuse * (1 - length(schlick)));
    return vec4(reflect, diffuse);
}
<@endfunc@>

<@func declareEvalBlinnRShading()@>

vec4 evalBlinnShading(vec3 fragNormal, vec3 fragLightDir, vec3 fragEyeDir, vec3 specular, float gloss) {
    // Diffuse Lighting
    float diffuseDot = dot(fragNormal, fragLightDir);
    float facingLight = step(0.0, diffuseDot);
    float diffuse = diffuseDot * facingLight;
 
    // Specular Lighting depends on the half vector and the gloss
    vec3 halfDir = normalize(fragEyeDir + fragLightDir);

    float specularPower = pow(facingLight * max(0.0, dot(halfDir, fragNormal)), gloss * 128.0);
    vec3 reflect = specularPower * specular;

    return vec4(reflect, diffuse);
}

<@endfunc@>


<$declareEvalPBRShading()$>


vec4 evalFragShading(vec3 fragNormal, vec3 fragLightDir, vec3 fragEyeDir, vec3 specular, float gloss) {

    /*if (gl_FragCoord.x > 1000) {
        return evalBlinnShading(fragNormal, fragLightDir, fragEyeDir, specular, gloss);
    } else {*/
        return evalPBRShading(fragNormal, fragLightDir, fragEyeDir, specular, gloss);
    //}
}

<@endif@>