​

varying vec2 vTexCoord;

uniform sampler2D uTexture0;

uniform sampler2D uTexture1;

​

uniform vec2 uResolution;

uniform vec2 uScale;

​

void main() {

​

  vec2 uv = vTexCoord;

  uv.y = 1.0 - uv.y;

  // The size of a single "texel"

  vec2 texelSize = 1.0 / uResolution;

  // How far from each texel should we check?

  vec2 offset = texelSize * uScale;

​

  // This is called a box blur. The gist of it is that we will sum up all of the neighbor pixels and then average them. 

  vec4 color = vec4(0.0);

  float kernel[9];

  // This is an emboss kernel

  kernel[0] = -2.0; kernel[1] = -1.0; kernel[2] = 0.0;

  kernel[3] = -1.0; kernel[4] = 1.0;  kernel[5] = 1.0;

  kernel[6] = 0.0;  kernel[7] = 1.0;  kernel[8] = 2.0;

  // Top left, top middle, top right

  color += texture2D(uTexture0, uv + vec2(-offset.x, -offset.y)) * kernel[0];

  color += texture2D(uTexture0, uv + vec2(0.0, -offset.y)) * kernel[1];

  color += texture2D(uTexture0, uv + vec2(offset.x, -offset.y)) * kernel[2];

  // Left, Middle, Right

  color += texture2D(uTexture0, uv + vec2(-offset.x, 0.0)) * kernel[3];

  color += texture2D(uTexture0, uv) * kernel[4];

  color += texture2D(uTexture0, uv + vec2(offset.x, 0.0)) * kernel[5];                              

  // Bottom left, bottom middle, bottom right

  color += texture2D(uTexture0, uv + vec2(-offset.x, offset.y)) * kernel[6];

  color += texture2D(uTexture0, uv + vec2(0.0, offset.y)) * kernel[7];

  color += texture2D(uTexture0, uv + vec2(offset.x, offset.y)) * kernel[8];    

  float kTotal = 0.0;

  // Get the total number of values in the kernel

  for(int i = 0; i<9; i++){

   kTotal += kernel[i]; 

  }

  // Divide by the kernel total

  color /= kTotal;

  // Send the color to the screen

  gl_FragColor = color;

​

}