xkcd Shader

xkcd.fx

sampler2D input : register(s0);

/// <summary>The second input texture.</summary>
/// <defaultValue>c:\examplefolder\examplefile.jpg</defaultValue> 
sampler2D RandomTexture : register(s1);

/// <summary>The radius of the Poisson disk (in pixels).</summary>
/// <minValue>1</minValue>
/// <maxValue>10</maxValue>
/// <defaultValue>5</defaultValue>
float DiskRadius : register(C0);

/// <summary>The size of the input (in pixels).</summary>
/// <type>Size</type>
/// <minValue>1,1</minValue>
/// <maxValue>1000,1000</maxValue>
/// <defaultValue>600,400</defaultValue>
float2 InputSize : register(C1);

/// <summary>Dampens the effect of the noise.</summary>
/// <minValue>1</minValue>
/// <maxValue>300</maxValue>
/// <defaultValue>100</defaultValue>
float Dampen : register(C2);

static const float2 poisson[12] = 
{
        float2(-0.326212f, -0.40581f),
        float2(-0.840144f, -0.07358f),
        float2(-0.695914f, 0.457137f),
        float2(-0.203345f, 0.620716f),
        float2(0.96234f, -0.194983f),
        float2(0.473434f, -0.480026f),
        float2(0.519456f, 0.767022f),
        float2(0.185461f, -0.893124f),
        float2(0.507431f, 0.064425f),
        float2(0.89642f, 0.412458f),
        float2(-0.32194f, -0.932615f),
        float2(-0.791559f, -0.59771f)
};

float4 blur(float2 uv)
{
  float4 cOut;

  // Center tap
  cOut = tex2D(RandomTexture, uv);
  for(int tap = 0; tap < 12; tap++)
  {
      float2 coord= uv.xy + (poisson[tap] / InputSize * DiskRadius);
      // Sample pixel
      cOut += tex2D(RandomTexture, coord);
  }

  return(cOut / 13.0f);
}

float4 main(float2 uv : TEXCOORD) : COLOR 
{ 
  float4 randomValue = blur(uv);
	
  uv.x += randomValue.x / Dampen;
  uv.y += randomValue.y / Dampen;
	
  float4 color = tex2D( input, uv );
  
  return color;
}