#ifdef GL_ES
precision mediump float;
#endif

uniform sampler2D   u_depth;
uniform sampler2D   u_buffer0;
uniform sampler2D   u_buffer1;

uniform vec2        u_resolution;
uniform vec2        u_mouse;
uniform float       u_time;

uniform bool        u_init;

varying vec2        v_texcoord;

float depthToSilhouette(float depth) {
  if(depth < 0.005) return 0;
  if(depth > 0.1) return 0;
  else return 1;
}

void main() {
  vec2 pixel = 1./u_resolution;
  vec2 offset[9];
  offset[0] = pixel * vec2(-1.0,-1.0);
  offset[1] = pixel * vec2( 0.0,-1.0);
  offset[2] = pixel * vec2( 1.0,-1.0);

  offset[3] = pixel * vec2(-1.0,0.0);
  offset[4] = pixel * vec2( 0.0,0.0);
  offset[5] = pixel * vec2( 1.0,0.0);

  offset[6] = pixel * vec2(-1.0,1.0);
  offset[7] = pixel * vec2( 0.0,1.0);
  offset[8] = pixel * vec2( 1.0,1.0);

  vec2 st = v_texcoord;
  // st.y = 1.0 - st.y;


#ifdef BUFFER_0
  // PING BUFFER
  //
  //  Note: Here is where most of the action happens. But need's to read
  //  te content of the previous pass, for that we are making another buffer
  //  BUFFER_1 (u_buffer1)
  vec4 color = vec4(0,0,0,1);
  if(u_init) {
    float tmp = texture2D(u_depth, st).r;
    color.rgb = vec3(depthToSilhouette(tmp));
  }
  else {

    float kernel[9];
    kernel[0] = 0.125;
    kernel[1] = 0.25;
    kernel[2] = 0.125;
    kernel[3] = 0.25;
    kernel[4] = 1.0;
    kernel[5] = 0.25;
    kernel[6] = 0.125;
    kernel[7] = 0.25;
    kernel[8] = 0.125;

    float lap = 0;

    for (int i=0; i < 9; i++){
      float tmp = texture2D(u_buffer1, st + offset[i]).r;
      lap += tmp * kernel[i] / 2.5;
    }
    color = vec4(vec3(lap * 2.0), 1.0);
  }

  gl_FragColor = color;

#elif defined( BUFFER_1 )
  // PONG BUFFER
  //
  //  Note: Just copy the content of the BUFFER0 so it can be 
  //  read by it in the next frame
  //
  gl_FragColor = texture2D(u_buffer0, st);
#else
  // Main Buffer
  float buf1 = texture2D(u_buffer1, st).r;
  vec3 dispColor = vec3(0, 0, 1);
  dispColor.rgb = vec3(depthToSilhouette(texture2D(u_depth, st).r));
 
  float maxVal = buf1;
  float minVal = buf1;
  for (int i=0; i < 9; i++){
    float tmp = texture2D(u_buffer1, st + offset[i]).r;
    maxVal = max(maxVal, tmp);
    minVal = min(minVal, tmp);
  }

  if(maxVal - minVal > 0.1) {
    dispColor.rgb = vec3(1);
  }

  // color.r = 1.;
  gl_FragColor = vec4(dispColor, 1.0);
#endif

}