uniform vec4 u_initialColor;

#if TEXTURE_UNITS > 0
uniform sampler2D u_dayTextures[TEXTURE_UNITS];
uniform vec4 u_dayTextureTranslationAndScale[TEXTURE_UNITS];
uniform bool u_dayTextureUseWebMercatorT[TEXTURE_UNITS];

#ifdef APPLY_ALPHA
uniform float u_dayTextureAlpha[TEXTURE_UNITS];
#endif

#ifdef APPLY_SPLIT
uniform float u_dayTextureSplit[TEXTURE_UNITS];
#endif

#ifdef APPLY_BRIGHTNESS
uniform float u_dayTextureBrightness[TEXTURE_UNITS];
#endif

#ifdef APPLY_CONTRAST
uniform float u_dayTextureContrast[TEXTURE_UNITS];
#endif

#ifdef APPLY_HUE
uniform float u_dayTextureHue[TEXTURE_UNITS];
#endif

#ifdef APPLY_SATURATION
uniform float u_dayTextureSaturation[TEXTURE_UNITS];
#endif

#ifdef APPLY_GAMMA
uniform float u_dayTextureOneOverGamma[TEXTURE_UNITS];
#endif

#ifdef APPLY_IMAGERY_CUTOUT
uniform vec4 u_dayTextureCutoutRectangles[TEXTURE_UNITS];
#endif

#ifdef APPLY_COLOR_TO_ALPHA
uniform vec4 u_colorsToAlpha[TEXTURE_UNITS];
#endif

uniform vec4 u_dayTextureTexCoordsRectangle[TEXTURE_UNITS];
#endif

#ifdef SHOW_REFLECTIVE_OCEAN
uniform sampler2D u_waterMask;
uniform vec4 u_waterMaskTranslationAndScale;
uniform float u_zoomedOutOceanSpecularIntensity;
#endif

#ifdef SHOW_OCEAN_WAVES
uniform sampler2D u_oceanNormalMap;
#endif

#if defined(ENABLE_DAYNIGHT_SHADING) || defined(GROUND_ATMOSPHERE)
uniform vec2 u_lightingFadeDistance;
#endif

#ifdef TILE_LIMIT_RECTANGLE
uniform vec4 u_cartographicLimitRectangle;
#endif

#ifdef GROUND_ATMOSPHERE
uniform vec2 u_nightFadeDistance;
#endif

#ifdef ENABLE_CLIPPING_PLANES
uniform sampler2D u_clippingPlanes;
uniform mat4 u_clippingPlanesMatrix;
uniform vec4 u_clippingPlanesEdgeStyle;
#endif

#if defined(FOG) && defined(DYNAMIC_ATMOSPHERE_LIGHTING) && (defined(ENABLE_VERTEX_LIGHTING) || defined(ENABLE_DAYNIGHT_SHADING))
uniform float u_minimumBrightness;
#endif

#ifdef COLOR_CORRECT
uniform vec3 u_hsbShift; // Hue, saturation, brightness
#endif

#ifdef HIGHLIGHT_FILL_TILE
uniform vec4 u_fillHighlightColor;
#endif

varying vec3 v_positionMC;
varying vec3 v_positionEC;
varying vec3 v_textureCoordinates;
varying vec3 v_normalMC;
varying vec3 v_normalEC;

#ifdef APPLY_MATERIAL
varying float v_height;
varying float v_slope;
varying float v_aspect;
#endif

#if defined(FOG) || defined(GROUND_ATMOSPHERE)
varying float v_distance;
varying vec3 v_fogRayleighColor;
varying vec3 v_fogMieColor;
#endif

#ifdef GROUND_ATMOSPHERE
varying vec3 v_rayleighColor;
varying vec3 v_mieColor;
#endif

vec4 sampleAndBlend(
    vec4 previousColor,
    sampler2D textureToSample,
    vec2 tileTextureCoordinates,
    vec4 textureCoordinateRectangle,
    vec4 textureCoordinateTranslationAndScale,
    float textureAlpha,
    float textureBrightness,
    float textureContrast,
    float textureHue,
    float textureSaturation,
    float textureOneOverGamma,
    float split,
    vec4 colorToAlpha)
{
    // This crazy step stuff sets the alpha to 0.0 if this following condition is true:
    //    tileTextureCoordinates.s < textureCoordinateRectangle.s ||
    //    tileTextureCoordinates.s > textureCoordinateRectangle.p ||
    //    tileTextureCoordinates.t < textureCoordinateRectangle.t ||
    //    tileTextureCoordinates.t > textureCoordinateRectangle.q
    // In other words, the alpha is zero if the fragment is outside the rectangle
    // covered by this texture.  Would an actual 'if' yield better performance?
    vec2 alphaMultiplier = step(textureCoordinateRectangle.st, tileTextureCoordinates);
    textureAlpha = textureAlpha * alphaMultiplier.x * alphaMultiplier.y;

    alphaMultiplier = step(vec2(0.0), textureCoordinateRectangle.pq - tileTextureCoordinates);
    textureAlpha = textureAlpha * alphaMultiplier.x * alphaMultiplier.y;

    vec2 translation = textureCoordinateTranslationAndScale.xy;
    vec2 scale = textureCoordinateTranslationAndScale.zw;
    vec2 textureCoordinates = tileTextureCoordinates * scale + translation;
    vec4 value = texture2D(textureToSample, textureCoordinates);
    vec3 color = value.rgb;
    float alpha = value.a;

#ifdef APPLY_COLOR_TO_ALPHA
    vec3 colorDiff = abs(color.rgb - colorToAlpha.rgb);
    colorDiff.r = max(max(colorDiff.r, colorDiff.g), colorDiff.b);
    alpha = czm_branchFreeTernary(colorDiff.r < colorToAlpha.a, 0.0, alpha);
#endif

#if !defined(APPLY_GAMMA)
    vec4 tempColor = czm_gammaCorrect(vec4(color, alpha));
    color = tempColor.rgb;
    alpha = tempColor.a;
#else
    color = pow(color, vec3(textureOneOverGamma));
#endif

#ifdef APPLY_SPLIT
    float splitPosition = czm_imagerySplitPosition;
    // Split to the left
    if (split < 0.0 && gl_FragCoord.x > splitPosition) {
       alpha = 0.0;
    }
    // Split to the right
    else if (split > 0.0 && gl_FragCoord.x < splitPosition) {
       alpha = 0.0;
    }
#endif

#ifdef APPLY_BRIGHTNESS
    color = mix(vec3(0.0), color, textureBrightness);
#endif

#ifdef APPLY_CONTRAST
    color = mix(vec3(0.5), color, textureContrast);
#endif

#ifdef APPLY_HUE
    color = czm_hue(color, textureHue);
#endif

#ifdef APPLY_SATURATION
    color = czm_saturation(color, textureSaturation);
#endif

    float sourceAlpha = alpha * textureAlpha;
    float outAlpha = mix(previousColor.a, 1.0, sourceAlpha);
    outAlpha += sign(outAlpha) - 1.0;

    vec3 outColor = mix(previousColor.rgb * previousColor.a, color, sourceAlpha) / outAlpha;

    // When rendering imagery for a tile in multiple passes,
    // some GPU/WebGL implementation combinations will not blend fragments in
    // additional passes correctly if their computation includes an unmasked
    // divide-by-zero operation,
    // even if it's not in the output or if the output has alpha zero.
    //
    // For example, without sanitization for outAlpha,
    // this renders without artifacts:
    //   if (outAlpha == 0.0) { outColor = vec3(0.0); }
    //
    // but using czm_branchFreeTernary will cause portions of the tile that are
    // alpha-zero in the additional pass to render as black instead of blending
    // with the previous pass:
    //   outColor = czm_branchFreeTernary(outAlpha == 0.0, vec3(0.0), outColor);
    //
    // So instead, sanitize against divide-by-zero,
    // store this state on the sign of outAlpha, and correct on return.

    return vec4(outColor, max(outAlpha, 0.0));
}

vec3 colorCorrect(vec3 rgb) {
#ifdef COLOR_CORRECT
    // Convert rgb color to hsb
    vec3 hsb = czm_RGBToHSB(rgb);
    // Perform hsb shift
    hsb.x += u_hsbShift.x; // hue
    hsb.y = clamp(hsb.y + u_hsbShift.y, 0.0, 1.0); // saturation
    hsb.z = hsb.z > czm_epsilon7 ? hsb.z + u_hsbShift.z : 0.0; // brightness
    // Convert shifted hsb back to rgb
    rgb = czm_HSBToRGB(hsb);
#endif
    return rgb;
}

vec4 computeDayColor(vec4 initialColor, vec3 textureCoordinates);
vec4 computeWaterColor(vec3 positionEyeCoordinates, vec2 textureCoordinates, mat3 enuToEye, vec4 imageryColor, float specularMapValue, float fade);

void main()
{
#ifdef TILE_LIMIT_RECTANGLE
    if (v_textureCoordinates.x < u_cartographicLimitRectangle.x || u_cartographicLimitRectangle.z < v_textureCoordinates.x ||
        v_textureCoordinates.y < u_cartographicLimitRectangle.y || u_cartographicLimitRectangle.w < v_textureCoordinates.y)
        {
            discard;
        }
#endif

#ifdef ENABLE_CLIPPING_PLANES
    float clipDistance = clip(gl_FragCoord, u_clippingPlanes, u_clippingPlanesMatrix);
#endif

    // The clamp below works around an apparent bug in Chrome Canary v23.0.1241.0
    // where the fragment shader sees textures coordinates < 0.0 and > 1.0 for the
    // fragments on the edges of tiles even though the vertex shader is outputting
    // coordinates strictly in the 0-1 range.
    vec4 color = computeDayColor(u_initialColor, clamp(v_textureCoordinates, 0.0, 1.0));

#ifdef SHOW_TILE_BOUNDARIES
    if (v_textureCoordinates.x < (1.0/256.0) || v_textureCoordinates.x > (255.0/256.0) ||
        v_textureCoordinates.y < (1.0/256.0) || v_textureCoordinates.y > (255.0/256.0))
    {
        color = vec4(1.0, 0.0, 0.0, 1.0);
    }
#endif

#if defined(SHOW_REFLECTIVE_OCEAN) || defined(ENABLE_DAYNIGHT_SHADING) || defined(HDR)
    vec3 normalMC = czm_geodeticSurfaceNormal(v_positionMC, vec3(0.0), vec3(1.0));   // normalized surface normal in model coordinates
    vec3 normalEC = czm_normal3D * normalMC;                                         // normalized surface normal in eye coordiantes
#endif

#if defined(ENABLE_DAYNIGHT_SHADING) || defined(GROUND_ATMOSPHERE)
    float cameraDist;
    if (czm_sceneMode == czm_sceneMode2D)
    {
        cameraDist = max(czm_frustumPlanes.x - czm_frustumPlanes.y, czm_frustumPlanes.w - czm_frustumPlanes.z) * 0.5;
    }
    else if (czm_sceneMode == czm_sceneModeColumbusView)
    {
        cameraDist = -czm_view[3].z;
    }
    else
    {
        cameraDist = length(czm_view[3]);
    }
    float fadeOutDist = u_lightingFadeDistance.x;
    float fadeInDist = u_lightingFadeDistance.y;
    if (czm_sceneMode != czm_sceneMode3D) {
        vec3 radii = czm_ellipsoidRadii;
        float maxRadii = max(radii.x, max(radii.y, radii.z));
        fadeOutDist -= maxRadii;
        fadeInDist -= maxRadii;
    }
    float fade = clamp((cameraDist - fadeOutDist) / (fadeInDist - fadeOutDist), 0.0, 1.0);
#else
    float fade = 0.0;
#endif

#ifdef SHOW_REFLECTIVE_OCEAN
    vec2 waterMaskTranslation = u_waterMaskTranslationAndScale.xy;
    vec2 waterMaskScale = u_waterMaskTranslationAndScale.zw;
    vec2 waterMaskTextureCoordinates = v_textureCoordinates.xy * waterMaskScale + waterMaskTranslation;
    waterMaskTextureCoordinates.y = 1.0 - waterMaskTextureCoordinates.y;

    float mask = texture2D(u_waterMask, waterMaskTextureCoordinates).r;

    if (mask > 0.0)
    {
        mat3 enuToEye = czm_eastNorthUpToEyeCoordinates(v_positionMC, normalEC);

        vec2 ellipsoidTextureCoordinates = czm_ellipsoidWgs84TextureCoordinates(normalMC);
        vec2 ellipsoidFlippedTextureCoordinates = czm_ellipsoidWgs84TextureCoordinates(normalMC.zyx);

        vec2 textureCoordinates = mix(ellipsoidTextureCoordinates, ellipsoidFlippedTextureCoordinates, czm_morphTime * smoothstep(0.9, 0.95, normalMC.z));

        color = computeWaterColor(v_positionEC, textureCoordinates, enuToEye, color, mask, fade);
    }
#endif

#ifdef APPLY_MATERIAL
    czm_materialInput materialInput;
    materialInput.st = v_textureCoordinates.st;
    materialInput.normalEC = normalize(v_normalEC);
    materialInput.slope = v_slope;
    materialInput.height = v_height;
    materialInput.aspect = v_aspect;
    czm_material material = czm_getMaterial(materialInput);
    color.xyz = mix(color.xyz, material.diffuse, material.alpha);
#endif

#ifdef ENABLE_VERTEX_LIGHTING
    float diffuseIntensity = clamp(czm_getLambertDiffuse(czm_lightDirectionEC, normalize(v_normalEC)) * 0.9 + 0.3, 0.0, 1.0);
    vec4 finalColor = vec4(color.rgb * czm_lightColor * diffuseIntensity, color.a);
#elif defined(ENABLE_DAYNIGHT_SHADING)
    float diffuseIntensity = clamp(czm_getLambertDiffuse(czm_lightDirectionEC, normalEC) * 5.0 + 0.3, 0.0, 1.0);
    diffuseIntensity = mix(1.0, diffuseIntensity, fade);
    vec4 finalColor = vec4(color.rgb * czm_lightColor * diffuseIntensity, color.a);
#else
    vec4 finalColor = color;
#endif

#ifdef ENABLE_CLIPPING_PLANES
    vec4 clippingPlanesEdgeColor = vec4(1.0);
    clippingPlanesEdgeColor.rgb = u_clippingPlanesEdgeStyle.rgb;
    float clippingPlanesEdgeWidth = u_clippingPlanesEdgeStyle.a;

    if (clipDistance < clippingPlanesEdgeWidth)
    {
        finalColor = clippingPlanesEdgeColor;
    }
#endif

#ifdef HIGHLIGHT_FILL_TILE
    finalColor = vec4(mix(finalColor.rgb, u_fillHighlightColor.rgb, u_fillHighlightColor.a), finalColor.a);
#endif

#if defined(FOG) || defined(GROUND_ATMOSPHERE)
    vec3 fogColor = colorCorrect(v_fogMieColor) + finalColor.rgb * colorCorrect(v_fogRayleighColor);
#ifndef HDR
    const float fExposure = 2.0;
    fogColor = vec3(1.0) - exp(-fExposure * fogColor);
#endif
#endif

#if defined(DYNAMIC_ATMOSPHERE_LIGHTING_FROM_SUN)
    vec3 atmosphereLightDirection = czm_sunDirectionWC;
#else
    vec3 atmosphereLightDirection = czm_lightDirectionWC;
#endif

#ifdef FOG
#if defined(DYNAMIC_ATMOSPHERE_LIGHTING) && (defined(ENABLE_VERTEX_LIGHTING) || defined(ENABLE_DAYNIGHT_SHADING))
    float darken = clamp(dot(normalize(czm_viewerPositionWC), atmosphereLightDirection), u_minimumBrightness, 1.0);
    fogColor *= darken;
#endif

#ifdef HDR
    const float modifier = 0.15;
    finalColor = vec4(czm_fog(v_distance, finalColor.rgb, fogColor, modifier), finalColor.a);
#else
    finalColor = vec4(czm_fog(v_distance, finalColor.rgb, fogColor), finalColor.a);
#endif
#endif

#ifdef GROUND_ATMOSPHERE
    if (czm_sceneMode != czm_sceneMode3D)
    {
        gl_FragColor = finalColor;
        return;
    }

#if defined(PER_FRAGMENT_GROUND_ATMOSPHERE) && defined(DYNAMIC_ATMOSPHERE_LIGHTING) && (defined(ENABLE_DAYNIGHT_SHADING) || defined(ENABLE_VERTEX_LIGHTING))
    float mpp = czm_metersPerPixel(vec4(0.0, 0.0, -czm_currentFrustum.x, 1.0), 1.0);
    vec2 xy = gl_FragCoord.xy / czm_viewport.zw * 2.0 - vec2(1.0);
    xy *= czm_viewport.zw * mpp * 0.5;

    vec3 direction = normalize(vec3(xy, -czm_currentFrustum.x));
    czm_ray ray = czm_ray(vec3(0.0), direction);

    vec3 ellipsoid_center = czm_view[3].xyz;

    czm_raySegment intersection = czm_rayEllipsoidIntersectionInterval(ray, ellipsoid_center, czm_ellipsoidInverseRadii);

    vec3 ellipsoidPosition = czm_pointAlongRay(ray, intersection.start);
    ellipsoidPosition = (czm_inverseView * vec4(ellipsoidPosition, 1.0)).xyz;
    AtmosphereColor atmosColor = computeGroundAtmosphereFromSpace(ellipsoidPosition, true, atmosphereLightDirection);

    vec3 groundAtmosphereColor = colorCorrect(atmosColor.mie) + finalColor.rgb * colorCorrect(atmosColor.rayleigh);
#ifndef HDR
    groundAtmosphereColor = vec3(1.0) - exp(-fExposure * groundAtmosphereColor);
#endif

    fadeInDist = u_nightFadeDistance.x;
    fadeOutDist = u_nightFadeDistance.y;

    float sunlitAtmosphereIntensity = clamp((cameraDist - fadeOutDist) / (fadeInDist - fadeOutDist), 0.0, 1.0);

#ifdef HDR
    // Some tweaking to make HDR look better
    sunlitAtmosphereIntensity = max(sunlitAtmosphereIntensity * sunlitAtmosphereIntensity, 0.03);
#endif

    groundAtmosphereColor = mix(groundAtmosphereColor, fogColor, sunlitAtmosphereIntensity);
#else
    vec3 groundAtmosphereColor = fogColor;
#endif

#ifdef HDR
    // Some tweaking to make HDR look better
    groundAtmosphereColor = czm_saturation(groundAtmosphereColor, 1.6);
#endif

    finalColor = vec4(mix(finalColor.rgb, groundAtmosphereColor, fade), finalColor.a);
#endif

    gl_FragColor = finalColor;
}

#ifdef SHOW_REFLECTIVE_OCEAN

float waveFade(float edge0, float edge1, float x)
{
    float y = clamp((x - edge0) / (edge1 - edge0), 0.0, 1.0);
    return pow(1.0 - y, 5.0);
}

float linearFade(float edge0, float edge1, float x)
{
    return clamp((x - edge0) / (edge1 - edge0), 0.0, 1.0);
}

// Based on water rendering by Jonas Wagner:
// http://29a.ch/2012/7/19/webgl-terrain-rendering-water-fog

// low altitude wave settings
const float oceanFrequencyLowAltitude = 825000.0;
const float oceanAnimationSpeedLowAltitude = 0.004;
const float oceanOneOverAmplitudeLowAltitude = 1.0 / 2.0;
const float oceanSpecularIntensity = 0.5;

// high altitude wave settings
const float oceanFrequencyHighAltitude = 125000.0;
const float oceanAnimationSpeedHighAltitude = 0.008;
const float oceanOneOverAmplitudeHighAltitude = 1.0 / 2.0;

vec4 computeWaterColor(vec3 positionEyeCoordinates, vec2 textureCoordinates, mat3 enuToEye, vec4 imageryColor, float maskValue, float fade)
{
    vec3 positionToEyeEC = -positionEyeCoordinates;
    float positionToEyeECLength = length(positionToEyeEC);

    // The double normalize below works around a bug in Firefox on Android devices.
    vec3 normalizedPositionToEyeEC = normalize(normalize(positionToEyeEC));

    // Fade out the waves as the camera moves far from the surface.
    float waveIntensity = waveFade(70000.0, 1000000.0, positionToEyeECLength);

#ifdef SHOW_OCEAN_WAVES
    // high altitude waves
    float time = czm_frameNumber * oceanAnimationSpeedHighAltitude;
    vec4 noise = czm_getWaterNoise(u_oceanNormalMap, textureCoordinates * oceanFrequencyHighAltitude, time, 0.0);
    vec3 normalTangentSpaceHighAltitude = vec3(noise.xy, noise.z * oceanOneOverAmplitudeHighAltitude);

    // low altitude waves
    time = czm_frameNumber * oceanAnimationSpeedLowAltitude;
    noise = czm_getWaterNoise(u_oceanNormalMap, textureCoordinates * oceanFrequencyLowAltitude, time, 0.0);
    vec3 normalTangentSpaceLowAltitude = vec3(noise.xy, noise.z * oceanOneOverAmplitudeLowAltitude);

    // blend the 2 wave layers based on distance to surface
    float highAltitudeFade = linearFade(0.0, 60000.0, positionToEyeECLength);
    float lowAltitudeFade = 1.0 - linearFade(20000.0, 60000.0, positionToEyeECLength);
    vec3 normalTangentSpace =
        (highAltitudeFade * normalTangentSpaceHighAltitude) +
        (lowAltitudeFade * normalTangentSpaceLowAltitude);
    normalTangentSpace = normalize(normalTangentSpace);

    // fade out the normal perturbation as we move farther from the water surface
    normalTangentSpace.xy *= waveIntensity;
    normalTangentSpace = normalize(normalTangentSpace);
#else
    vec3 normalTangentSpace = vec3(0.0, 0.0, 1.0);
#endif

    vec3 normalEC = enuToEye * normalTangentSpace;

    const vec3 waveHighlightColor = vec3(0.3, 0.45, 0.6);

    // Use diffuse light to highlight the waves
    float diffuseIntensity = czm_getLambertDiffuse(czm_lightDirectionEC, normalEC) * maskValue;
    vec3 diffuseHighlight = waveHighlightColor * diffuseIntensity * (1.0 - fade);

#ifdef SHOW_OCEAN_WAVES
    // Where diffuse light is low or non-existent, use wave highlights based solely on
    // the wave bumpiness and no particular light direction.
    float tsPerturbationRatio = normalTangentSpace.z;
    vec3 nonDiffuseHighlight = mix(waveHighlightColor * 5.0 * (1.0 - tsPerturbationRatio), vec3(0.0), diffuseIntensity);
#else
    vec3 nonDiffuseHighlight = vec3(0.0);
#endif

    // Add specular highlights in 3D, and in all modes when zoomed in.
    float specularIntensity = czm_getSpecular(czm_lightDirectionEC, normalizedPositionToEyeEC, normalEC, 10.0);
    float surfaceReflectance = mix(0.0, mix(u_zoomedOutOceanSpecularIntensity, oceanSpecularIntensity, waveIntensity), maskValue);
    float specular = specularIntensity * surfaceReflectance;

#ifdef HDR
    specular *= 1.4;

    float e = 0.2;
    float d = 3.3;
    float c = 1.7;

    vec3 color = imageryColor.rgb + (c * (vec3(e) + imageryColor.rgb * d) * (diffuseHighlight + nonDiffuseHighlight + specular));
#else
    vec3 color = imageryColor.rgb + diffuseHighlight + nonDiffuseHighlight + specular;
#endif

    return vec4(color, imageryColor.a);
}

#endif // #ifdef SHOW_REFLECTIVE_OCEAN