Fusion 8: Rebuilding beauty pass does not match


#1

Hi all

So I’m rebuilding my beauty pass from my separate channels and using the merge to add them together.
I’m working Linear and in float so I also have my LUT enabled and set gamma 2.2 so I can see what I’m doing.

So there doesnt seem to be an “ADD” mode in the merge, so I’m using “SCREEN” mode. Is that the correct one to use?

So what I’m doing is adding (screen-ing) all these together with merge nodes
GI
Lighting
Reflection
Refraction
Specular

I then compare that to my Beauty and it’s pretty close, but when I do an A/B compare I can see they don’t match 100%. It’s about a 97% match

The same thing in Photoshop works just fine with the layer blending mode set to Linear Dodge-ADD
Also tried Natron and in there it also works just fine with the merge nodes set to Plus.

So what am I doing wrong in Fusion? Only thing I can think of is the SCREEN mode is not the correct merge…


#2

you can achieve “add” in the merge with the “Normal” mode and alpha gain = 0

becuase “over” or “normal” (in fusion) is A+B*(1-A_alpha), if you set the influence/gain of the alpha to 0 you get A+B
you can also use the channel boolean node and set it to add