Fog Pixel Shader

Each pixel is blended with fog color. The bigger pixel distance from observer location - the more pixel color approaches fog color. GLSL fragment code:

---

uniform sampler2D tex;

void main()
{
 float FogDensity = 10.;
 vec4 FogColor = vec4(0.4,0.2,0.2,1.0);
 vec4 CurrentColor = texture2D(tex, gl_TexCoord[0].xy);

  // distance to target
 float FogDistance = distance(vec2(0.49,0.46),gl_TexCoord[0].xy);
 
 // fog factor
 float FogFactor = exp(-abs(FogDistance * FogDensity));

 // linear blend between fog color and pixel color
 gl_FragColor = mix(FogColor,CurrentColor,FogFactor);
}

---

Image

and after fog shader applied: