// Thanks for the contribution Jonas
// http://29a.ch/2012/7/19/webgl-terrain-rendering-water-fog

uniform sampler2D specularMap;
uniform sampler2D normalMap;
uniform vec4 baseWaterColor;
uniform vec4 blendColor;
uniform float frequency;
uniform float animationSpeed;
uniform float amplitude;
uniform float specularIntensity;
uniform float fadeFactor;

czm_material czm_getMaterial(czm_materialInput materialInput)
{
    czm_material material = czm_getDefaultMaterial(materialInput);

    float time = czm_frameNumber * animationSpeed;

    // fade is a function of the distance from the fragment and the frequency of the waves
    float fade = max(1.0, (length(materialInput.positionToEyeEC) / 10000000000.0) * frequency * fadeFactor);

    float specularMapValue = texture2D(specularMap, materialInput.st).r;

    // note: not using directional motion at this time, just set the angle to 0.0;
    vec4 noise = czm_getWaterNoise(normalMap, materialInput.st * frequency, time, 0.0);
    vec3 normalTangentSpace = noise.xyz * vec3(1.0, 1.0, (1.0 / amplitude));

    // fade out the normal perturbation as we move further from the water surface
    normalTangentSpace.xy /= fade;

    // attempt to fade out the normal perturbation as we approach non water areas (low specular map value)
    normalTangentSpace = mix(vec3(0.0, 0.0, 50.0), normalTangentSpace, specularMapValue);

    normalTangentSpace = normalize(normalTangentSpace);

    // get ratios for alignment of the new normal vector with a vector perpendicular to the tangent plane
    float tsPerturbationRatio = clamp(dot(normalTangentSpace, vec3(0.0, 0.0, 1.0)), 0.0, 1.0);

    // fade out water effect as specular map value decreases
    material.alpha = mix(blendColor.a, baseWaterColor.a, specularMapValue) * specularMapValue;

    // base color is a blend of the water and non-water color based on the value from the specular map
    // may need a uniform blend factor to better control this
    material.diffuse = mix(blendColor.rgb, baseWaterColor.rgb, specularMapValue);

    // diffuse highlights are based on how perturbed the normal is
    material.diffuse += (0.1 * tsPerturbationRatio);

    material.diffuse = material.diffuse;

    material.normal = normalize(materialInput.tangentToEyeMatrix * normalTangentSpace);

    material.specular = specularIntensity;
    material.shininess = 10.0;

    return material;
}