uniform sampler2D background_tex;
uniform sampler2D noise_tex;
uniform float     radius;
varying vec2      tex_coord;

void main()
{
  float x_dist = tex_coord.x - 0.5f;
  float y_dist = tex_coord.y - 0.5f;
  float dist   = sqrt(x_dist*x_dist + y_dist*y_dist);

  if (dist > radius || dist < radius - 164.0/512.0) {
    //gl_FragColor = texture2D(background_tex, tex_coord.xy);
    discard;
  } else {
    vec4 uv_col  = texture2D(noise_tex, tex_coord.xy*1.5f);
    float b = 1.0f - clamp((radius - dist)*512.0f/164.0f, 0, 1.0f);
    float h = b * b;

    float highlight = 1.0f - clamp((radius - dist)*512.0f/32.0f, 0, 1.0f);

    vec4 col2 = texture2D(background_tex, tex_coord.xy + (uv_col.rb * uv_col.g) * h * 0.3f);
        vec4 col = col2;
    col += vec4(h * uv_col.r + highlight*0.9,
                h * uv_col.r + highlight*0.9,
                h*1.5f * uv_col.r + highlight, 
                h);

   col.a = pow(b, 0.5);

    gl_FragColor = col;
      }
}