Eye Adaptation

float4  adaptPass (in float4 pos : SV_Position, in float2 texcoord : TEXCOORD0) : SV_Target
{
    float4  Lum             =   tex2D(samplerBloom4, 0.5);
            Lum.w           =   max(Lum.x, max(Lum.y, Lum.z));
            
    float4  Color           =   tex2D(samplerColor, texcoord);
            Color.w         =   max(Color.x, max(Color.y, Color.z));        
            
    float   adaptLum        =   Lum.w;
    float   adaptCol        =   Color.w;
    
    if  (adaptCol > adaptLum)
    {
        float   difference  =   adaptCol / adaptLum;
        float3  brightness  =   pow(color.xyz, difference);
    }
    
    if  (adaptCol < adaptLum)
    {
        float   difference  =   adaptLum / adaptCol;
        float3  brightness  =   color.xyz + difference;
    }
    
    //      color.xyz       =   lerp(color.xyz, brightness, timer);
            color.xyz       =   lerp(color.xyz, brightness, smoothstep(0, timeleft, timer));
            color.w         =   1.0;
return      color;
}

(1 - timeleft) * adaptSpeed

float4  Lum             =   tex2D(samplerBloom4, 0.5);

float3 val3 = 5; // val3 == float3(5, 5, 5)
float4 val4 = float2(1, 2); // val4 == float4(1, 2, 2, 2)