Pretty sure some others have implemented something similar, but it was kinda fun building up something myself.


The problem with the standard overlay blend mode is the screen blending part of the equation.
Wich can result in some illegal pixels when using it in combination with hdri data.

Since it its a hit and miss you usually avoid overlay when dealing with high dynamic range content.

This node uses an add instead of the screen function for values above 1.0.

So basically it does this:

if fg <0.5
    result = bg* 2.0* fg
else
    if (fg < 1.0)
        result = bg + (((fg -0.5)*2.0) * fg)
    else
        result = bg +fg


Another experimental option to shift the midpoint (0.5) has been added. not sure if there is any use for it. But since its easy to implement I see no reason why I should not.

And since its fun to do I also added a "backdrop function split", so the blending is divided by the background value instead of the foreground.
Got some trippy results here, but I'm not sure if there is a real world usage to this

and sorry for the name, but the alternatives
hoverlay
hdrlayover
overlord
didn't sound fitting.

maybe overadd ?

Version 0.1

Initial implementation

Parameters

Overlay Type
Top is the standard behaviour, while Backdrop uses the BG image for blending. Not sure if there is any use for it

Mix
The amount the foregroudn is mixed with the background

Midpoint
You can shift the midpoint (where it starts to multtiply / add)