float chebyshevUpperBound()
{
vec2 moments = texture2D(ShadowMap,ShadowCoordPostW.xy).rg;
// Surface is fully lit. as the current fragment is before the light occluder
if (ShadowCoordPostW.z <= moments.x)
return 1.0 ;
// The fragment is either in shadow or penumbra. We now use chebyshev's upperBound to check
// How likely this pixel is to be lit (p_max)
float variance = moments.y - (moments.x*moments.x);
variance = max(variance,0.1);
float d = ShadowCoordPostW.z - moments.x;
float p_max = (variance / (variance + d*d));
return max(p_max, 0.4);
}
//Color computation in main()
shadow = chebyshevUpperBound();
fragColor = ((ambient_color + diffuse_color * diffuse_value))*texel;
fragColor.rgb *= shadow;