xue yue

Also this SDR-Video is an additional tonemapping on top of aces as far as I know.
You would need to the same ACES Profile in Nuke and the same tonemapping applied to get the same image result.

If I understand you right, something like this could work:
You can edit the parameter interface and add an integer parameter that you reference in your expression. Also you would be able to animate this value to your liking.
Is that what you meant?

I just used a packed fractured object and v@v instead of v@vel (which is the name for velocity volumes).

Also v@P.y is not the centroid, it is the y-position of every Point your wrangle runs on. If you need to do it without the packed object (which is slower than the packed sim) you can use the Extract Centroid SOP to get the centroid of every connected piece and use this instead v@P.y in the wrangle.