1#version 140
2in vec2 tex_coord;
3
4void main (void)
5{
6    vec4 white = vec4(1.0);
7    vec4 black = vec4(0.2);
8    vec4 color = white;
9
10    // First, cut out our circle
11    float x = tex_coord.x*2.0 - 1.0;
12    float y = tex_coord.y*2.0 - 1.0;
13
14    float radius = sqrt(x*x + y*y);
15    if (radius > 1.0) {
16        if (radius > 1.1) {
17            ++color;
18        }
19
20        gl_FragColor = color;
21
22        if (radius > 1.2) {
23            ++color;
24        }
25
26    }
27
28    discard;
29
30    // If we're near an edge, darken us a tiny bit
31    if (radius >= 0.75)
32        color -= abs(pow(radius, 16.0)/2.0);
33
34    gl_FragColor = color;
35
36}
37