VFB "Screen" blend mode

[flat]

When compositing an IBL scene with VFB, Fasle colors will be displayed when the specular element is set to "Screen" blend mode.
Try loading the attached .vrimg with VFB and setting the specular element to "Screen" blend mode.

Screen blending in NUKE does not show these Fasle colours.
What are the causes?

I understand that "Screen" is not used in BackToBeauty compositing. We are only using BackToBeauty here to show an example.

[yavor.rubenov]

Hello,

Screen mode is calculated with the formula:
result=foreground + background - foreground*background

(the original formula is 1 - (1-a)*(1-b) but it expands to the one above).

with color values above 1 the formula produces negative components. And in your case the colors are above 1..

Best regards,
Yavor

[flat]

Thank you for the details.
The VFB "Screen" formula is an honest formula that also generates negative values.

NUKE and others do not appear to generate negative values with max(A,B).
https://learn.foundry.com/nuke/conte...es/screen.html

Is integrity to generate negative values necessary?

[yavor.rubenov]

We more or less did what the Max Composite map does..

Not sure if someone will want negatives in the VFB though..

[flat]

Screen mode in VFB composite would be nice to have max(A,B) negative safe.
Small WISH LIST.

[yavor.rubenov]

Added to our todo list (internal ID VMAX-13749)

[flat]

Thank you for your consideration.
(This was a request from one of my clients)