attribute vec3 position;
attribute vec3 normal;
attribute vec4 color;
uniform   mat4 mvpMatrix;
uniform   mat4 invMatrix;
uniform   vec3 lightDirection;
uniform   vec3 eyeDirection;
uniform   vec4 ambientColor;
varying   vec4 vColor;

void main(void){
    vec3  invLight = normalize(invMatrix * vec4(lightDirection, 0.0)).xyz;
    vec3  invEye   = normalize(invMatrix * vec4(eyeDirection, 0.0)).xyz;
    vec3  halfLE   = normalize(invLight + invEye);
    float diffuse  = clamp(dot(normal, invLight), 0.0, 1.0);
    float specular = pow(clamp(dot(normal, halfLE), 0.0, 1.0), 50.0);
    vec4  light    = color * vec4(vec3(diffuse), 1.0) + vec4(vec3(specular), 1.0);
    vColor         = light + ambientColor;
    gl_Position    = mvpMatrix * vec4(position, 1.0);
}