Problems with shader scripting

[anonymous_user_d84154a2]

Hi all,

I am working on a post processing shader for a multi monitor setup. I need to position things pixel perfect but I run into troubles. My test setup are two screens with a 1920 pxl width with a 140pxl bezel compensation. Total view size is therefore 3980 x 1200.

I plug together a simple shader in blueprint that looks like this:

In theory this creates a white screen on the left and a black screen on the right. However, if I take a screenshot and look at it in Photoshop the border between the white on the left and the black on the right is not in the middle of the image. It should be at 1990 pxl - in the middle - but actually it is at 1992 pxl - two pixels shifted to the right.

I need to position things precisely. So, what is wrong here and how can I correct this?

Thanks for you time

Jens

[Hannes3112]

I see what you mean; apparently most of the UV values are not accurate.
My screen is 1920x1200 but the View Size returns 1920.0016 x 1200.0010.
So if you have a very large screen like 4K or a dual screen setup this might introduce rounding problems.

[Hannes3112]

Found the real problem:
Using Nvidia Bezel Compensation on Multi-Monitor Systems allows to create non power of 2 Width and Heights. Than UV Calculations are of.
Not sure if its Nvidia doing some background compensation or unreal but using correct values fixes the problem.