Outline Postprocessing Effect - Nyuuzero

/*
* Simple outline postprocessing effect
* Author: nyuuzero
*/

uniform sampler2D sampler0;
uniform sampler2D sampler1;
uniform sampler2D sampler2;

uniform float displayWidth;
uniform float displayHeight;
uniform float aspectRatio;
uniform float near;
uniform float far;

float rand(vec2 co){
    return fract(sin(dot(co.xy ,vec2(12.9898,78.233))) * 43758.5453);
}

float getLinearDepth(vec2 coords)
{
   return (2 * near) / (far + near - texture2D( sampler1, coords ).x * (far - near));
}

float generateOutline(vec2 coords)
{
   // pixelsize
   float horizontalPixelSize = 1.0 / displayWidth;
   float verticalPixelSize = 1.0 / displayHeight;

   // generate outline
   float tempDepth =
      getLinearDepth(coords + vec2(horizontalPixelSize,verticalPixelSize)) +
      getLinearDepth(coords + vec2(-horizontalPixelSize,verticalPixelSize)) +
      getLinearDepth(coords + vec2(0.0,-verticalPixelSize));

   tempDepth /= 3;

   return getLinearDepth(coords)-tempDepth;
}

void main()
{
   gl_FragColor = mix(texture2D( sampler0, gl_TexCoord[0].st ),vec4(0.0,0.0,0.0,0.0),clamp(generateOutline(gl_TexCoord[0].st)*100,0.0,0.9));
   //gl_FragColor *= 1.0 - clamp(generateOutline(gl_TexCoord[0].st)*100,0.0,1.0);
}