/**
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* Calculates the specular intensity of reflected light.
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*
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* @name czm_getSpecular
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* @glslFunction
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*
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* @param {vec3} lightDirectionEC Unit vector pointing to the light source in eye coordinates.
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* @param {vec3} toEyeEC Unit vector pointing to the eye position in eye coordinates.
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* @param {vec3} normalEC The surface normal in eye coordinates.
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* @param {float} shininess The sharpness of the specular reflection. Higher values create a smaller, more focused specular highlight.
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*
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* @returns {float} The intensity of the specular highlight.
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*
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* @see czm_phong
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*
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* @example
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* float diffuseIntensity = czm_getLambertDiffuse(lightDirectionEC, normalEC);
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* float specularIntensity = czm_getSpecular(lightDirectionEC, toEyeEC, normalEC, 200);
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* vec3 color = (diffuseColor * diffuseIntensity) + (specularColor * specularIntensity);
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*/
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float czm_getSpecular(vec3 lightDirectionEC, vec3 toEyeEC, vec3 normalEC, float shininess)
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{
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vec3 toReflectedLight = reflect(-lightDirectionEC, normalEC);
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float specular = max(dot(toReflectedLight, toEyeEC), 0.0);
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// pow has undefined behavior if both parameters <= 0.
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// Prevent this by making sure shininess is at least czm_epsilon2.
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return pow(specular, max(shininess, czm_epsilon2));
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}
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