source: data/branches/Shader_HS18/programs/Example/GLSL150/HeatBlurFp.glsl @ 12083

#version 150

uniform sampler2D Input;
uniform vec4 blurAmount;

in vec2 uv;
out vec4 fragColour;

void main()
{
   int i;
   vec4 tmpOutColor;
   float  diffuseGlowFactor;
   vec2 offsets[4];
/*
                // hazy blur
                -1.8, -1.8,
                -1.8, 1.8,
                1.8, -1.8,
                1.8, 1.8
*/
/*
                // less-hazy blur
          -1.0,  2.0,
          -1.0, -1.0,
           1.0, -1.0,
           1.0,  1.0
*/
/*
      -0.326212, -0.405805,
      -0.840144, -0.073580,
      -0.695914,  0.457137,
      -0.203345,  0.620716
*/

   offsets[0] = vec2(-0.3,  0.4);
   offsets[1] = vec2(-0.3,  -0.4);
   offsets[2] = vec2(0.3,  -0.4);
   offsets[3] = vec2(0.3,  0.4);

   tmpOutColor = texture( Input, uv );  // UV coords are in image space

   // calculate glow amount
   diffuseGlowFactor = 0.0113 * (2.0 - max( tmpOutColor.r, tmpOutColor.g ));

   // basic blur filter
   for (i = 0; i < 4; i++) {
      tmpOutColor += texture( Input, uv + blurAmount.x * diffuseGlowFactor * offsets[i] );
   }

   tmpOutColor *= 0.25;

   // TIPS (old-skool strikes again!)
   // Pay attention here! If you use the "out float4 outColor" directly
   // in your steps while creating the output color (like you remove
   // the "tmpOutColor" var and just use the "outColor" directly)
   // your pixel-color output IS CHANGING EACH TIME YOU DO AN ASSIGNMENT TOO!
   // A temporary variable, instead, acts like a per-pixel double buffer, and
   // best of all, lead to better performance.
   fragColour = tmpOutColor;
}