uniform vec3 col;

#vertex

uniform vec4 rgio;
uniform vec2 zctl;

void main() {
    vec2 rg;
    vec3 n;
    vec4 v;
    float i, z;

    // determine if we're on the inner or outer side
    if (gl_Color.a < 0.5)
        rg = rgio.xy;
    else
        rg = rgio.zw;

    // compute vertex
    v = gl_ModelViewMatrix
      * vec4(rg.r * normalize(mix(gl_Color.xyz, gl_Vertex.xyz, rg.g)), 1.0);
    gl_Position = gl_ProjectionMatrix * v;

    // compute z
    z = abs(zctl.x + v.z) * zctl.y;

    // compute normal and lighting
    n = normalize(gl_NormalMatrix * gl_Normal);
    i = max(dot(n, normalize(vec3(gl_LightSource[0].position))), 0.0)
        * gl_LightSource[0].diffuse.r;
    i *= rg.r;
    i = 1.0 - i;
    i = gl_LightModel.ambient.r + 1.0 - i * i;
    gl_FrontColor = vec4(i * col, z);
}

#fragment

uniform sampler2D tex;

void main() {
    float t = 1.0 - gl_Color.r;
    t *= t;
    t *= t;
    gl_FragColor = vec4(mix(gl_Color.rgb,
                            0.125 * texture2D(tex, 0.125 * gl_FragCoord.xy).rgb,
                            t),
                        gl_Color.a);
//    gl_FragColor = vec4(gl_Color.a, gl_Color.a, gl_Color.a, 0.0);
//    gl_FragColor = vec4(gl_Color.a, gl_Color.a, gl_Color.a, gl_Color.a);
}