<!
//  DeferredGlobalLight.slh
//  libraries/render-utils/src
//
//  Created by Sam Gateau on 2/5/15.
//  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_GLOBAL_LIGHT_SLH@>
<@def DEFERRED_GLOBAL_LIGHT_SLH@>

<@include DeferredLighting.slh@>


struct SphericalHarmonics {
    vec4 L00;
    vec4 L1m1;
    vec4 L10;
    vec4 L11;
    vec4 L2m2;
    vec4 L2m1;
    vec4 L20;
    vec4 L21;
    vec4 L22;
};

vec4 evalSphericalLight(SphericalHarmonics sh, vec3 direction ) {

    vec3 dir = direction.xzy; // we don;t understand why yet but we need to use z as vertical axis?

    const float C1 = 0.429043;
    const float C2 = 0.511664;
    const float C3 = 0.743125;
    const float C4 = 0.886227;
    const float C5 = 0.247708;

    vec4 value = C1 * sh.L22 * (dir.x * dir.x - dir.y * dir.y) + 
                        C3 * sh.L20 * dir.z * dir.z + 
                        C4 * sh.L00 - C5 * sh.L20 + 
                        2.0 * C1 * (   sh.L2m2 * dir.x * dir.y + 
                                    sh.L21  * dir.x * dir.z + 
                                    sh.L2m1 * dir.y * dir.z ) + 
                        2.0 * C2 * (   sh.L11  * dir.x + 
                                    sh.L1m1 * dir.y + 
                                    sh.L10  * dir.z ) ; 
    return value;
}

// Need one SH
uniform SphericalHarmonics ambientSphere;

// Everything about light
<@include model/Light.slh@>

// The view Matrix
uniform mat4 invViewMat;

vec3 evalAmbienGlobalColor(float shadowAttenuation, vec3 position, vec3 normal, vec3 diffuse, vec3 specular, float gloss) {

    // Need the light now
    Light light = getLight();

    vec3 fragNormal = vec3(invViewMat * vec4(normal, 0.0));
    vec4 fragEyeVector = invViewMat * vec4(-position, 0.0);
    vec3 fragEyeDir = normalize(fragEyeVector.xyz);

    vec3 color = diffuse.rgb * getLightColor(light) * getLightAmbientIntensity(light);

    vec4 shading = evalFragShading(fragNormal, -getLightDirection(light), fragEyeDir, specular, gloss);

    color += vec3(diffuse + shading.rgb) * shading.w * shadowAttenuation * getLightColor(light) * getLightIntensity(light);

    return color;
}
vec3 evalAmbienSphereGlobalColor(float shadowAttenuation, vec3 position, vec3 normal, vec3 diffuse, vec3 specular, float gloss) {
    // Need the light now
    Light light = getLight();
    
    vec3 fragNormal = normalize(vec3(invViewMat * vec4(normal, 0.0)));
    vec4 fragEyeVector = invViewMat * vec4(-position, 0.0);
    vec3 fragEyeDir = normalize(fragEyeVector.xyz);
    
    vec3 ambientNormal = fragNormal.xyz;
    vec3 color = diffuse.rgb * evalSphericalLight(ambientSphere, ambientNormal).xyz * getLightAmbientIntensity(light);

    vec4 shading = evalFragShading(fragNormal, -getLightDirection(light), fragEyeDir, specular, gloss);

    color += vec3(diffuse + shading.rgb) * shading.w * shadowAttenuation * getLightColor(light) * getLightIntensity(light);

    return color;
}

vec3 evalLightmappedColor(float shadowAttenuation, vec3 normal, vec3 diffuse, vec3 lightmap) {
    
    Light light = getLight();

    vec3 fragNormal = vec3(invViewMat * vec4(normal, 0.0));
    float diffuseDot = dot(fragNormal, -getLightDirection(light));

    // need to catch normals perpendicular to the projection plane hence the magic number for the threshold
    // it should be just 0, but we have innacurracy so we need to overshoot
    const float PERPENDICULAR_THRESHOLD = -0.005;
    float facingLight = step(PERPENDICULAR_THRESHOLD, diffuseDot); 
    //float facingLight = step(PERPENDICULAR_THRESHOLD, diffuseDot); 
        
    // evaluate the shadow test but only relevant for light facing fragments
    float lightAttenuation = (1 - facingLight) + facingLight * shadowAttenuation;
            
    // diffuse light is the lightmap dimmed by shadow
    vec3 diffuseLight = lightAttenuation * lightmap;

    // ambient is a tiny percentage of the lightmap and only when in the shadow
    vec3 ambientLight = (1 - lightAttenuation) * lightmap * getLightAmbientIntensity(light); 

    return diffuse * (ambientLight +  diffuseLight);
}

<@endif@>