varying vec3 n, l, h;

#vertex

void main() {
    // normal vector, light direction, half vector
    n = normalize(gl_NormalMatrix * gl_Normal);
    l = normalize(vec3(gl_LightSource[0].position) - vec3(gl_ModelViewMatrix * gl_Vertex));
    h = normalize(gl_LightSource[0].halfVector.xyz);

    // the rest
    gl_FrontColor = gl_Color;
    gl_TexCoord[0] = gl_MultiTexCoord0;
    gl_Position = ftransform();
}

#fragment

uniform sampler2D tex;

void main() {
    float d;
    vec3 nn;
    vec4 col = gl_Color * gl_LightModel.ambient;

    // lighting
    nn = normalize(n);
    nn = normalize(nn + 0.5 * (texture2D(tex, gl_TexCoord[0].xy).xyz - vec3(0.5, 0.5, 0.5)));
    d = dot(nn, normalize(l));
    if (d > 0.0) {
        col += gl_Color * d;
        d = dot(nn, normalize(h));
        if (d > 0.0)
            col += gl_FrontMaterial.specular * pow(d, gl_FrontMaterial.shininess);
    }
    gl_FragColor = col;
}