expression to get the actual preview resolution, roughen edges issues

[Tomas Bumbulevičius]

Hey Arne – unlikely to be possible. As Preview Resolution is project panel item, it can be access from scripting only.

Do you render different resolution outputs? Does it mean that half/quarter of best quality would look completely different?

[Arne Münch]

Hi Tomas
Yes indeed. Different render resolutions look different.
I had a 4k project sending HD files to the customer as a preview, they look even different from my half HD preview working space, but the difference was not too much.
For the final render in 4K it really looked bad in my eyes.
Kind of silly. The turbulent distort effect for example does not have that behavior.

[Filip Vandueren]

I thought I could do a clever trick like doing sampleImage on a 1×1 white pixel, which gets grayer and grayer or more transparant as the resolution drops, but unexpectedly, the numbers sampleImage() yields always gives the correct result of what it looks like at full res ??‍♂️

[Arne Münch]

Hi Filip
Thanks for the nice approach. Good to know that other people struggle with the same issue:)

For me it really degrades the use of that effect a bit and I will try to use turbulent distort instead when possible.

But when you need to use it a lot in a project here is what you can do:
Create in the “MasterComp” of the project an Null named “Control” withe a slider named “render res”.
Every roughen edges effect becomes the following expression on the scale property of the effect (just copying the whole effect once create to other layers or create a simple preset):

value * (1/(Math.pow(2, comp("MasterComp").layer("Control").effect("render res")(1))))

Then when working and rendering in full, set the full res slider to 0, when working and rendering in half, set it to 1, when working and rendering in quarter set it to 2 and so on.
This way you can easily change all roughen edges effects by a correct multiplier with just one click, to match roughly the desired look.