#version 130

uniform vec4 ambientColor;
uniform vec4 diffuseColor;
uniform vec4 specularColor;
uniform float ambientReflection;
uniform float diffuseReflection;
uniform float specularReflection;
uniform float shininess;
uniform sampler2D texture;

in vec3 varyingNormal;
in vec3 varyingLightDirection;
in vec3 varyingViewerDirection;
in vec2 varyingTextureCoordinate;

out vec4 fragColor;

void main(void)
{
    vec3 normal = normalize(varyingNormal);
    vec3 lightDirection = normalize(varyingLightDirection);
    vec3 viewerDirection = normalize(varyingViewerDirection);
    vec4 ambientIllumination = ambientReflection * ambientColor;
    vec4 diffuseIllumination = diffuseReflection * max(0.0, dot(lightDirection, normal)) * diffuseColor;
    vec4 specularIllumination = specularReflection * pow(max(0.0, dot(-reflect(lightDirection, normal), viewerDirection)), shininess) * specularColor;
    fragColor = texture2D(texture, varyingTextureCoordinate) * (ambientIllumination + diffuseIllumination) + specularIllumination;
}