Why is the Duplicate node not showing all its copies?

I'm trying to understand the behavior of the Duplicate node. I wanted to make a trail of white dots with it by offsetting the center and increasing the number of copies.

I expected to get a trail of dots. Instead, I see the first dot and the last dot from the trail. Why does this happen and how can I achieve my expected result?

Huh. This is really weird. I see the same. When I have Center->X = 0.6 in the Duplicate node, all the copies disappear.

A simple workaround is to use a slightly difference value for Center->X, like 0.60001. It also works when changing any other value, like Size or Angle or Y.

It also happens with Center->Y = 0.6, or either of them at 0.7, 0.8, 0.9. Likewise 0.65, 0.75. it seems any multiple of 0.05.

At first I thought maybe there was a logical explanation for this. But what's even weirder is the problem is fixed by manipulating any other control, including Blend, Burn In, Subtractive/Additive. The smallest tweak to any of those controls will cause all the copies to appear as expected!

So it sure feels like a bug? Unless there's some weird interaction going on here I can't figure out? Hopefully an expert will chip in and confirm

PS. I tested in Fusion Studio 16.2.4, so if an issue exists it's common to both Resolve and Fusion Studio.

Okay, thanks for confirming it's unusual. I'm currently running DaVinci Resolve 16.2.7.010 on Windows and I can confirm that the workaround seems to do the trick for now. Like you, I'm still curious to find out what the reason for this behavior is.

I discovered this strange behaviour myself literally minutes ago while playing with the Duplicate node in Fusion 16.2.4

Courious to know if it's a feature, a bug or user error

It's got to be a bug. I just tested in Fusion 9 and it works fine there, as expected.



I'd actually forgotten that Duplicate isn't even a full tool, it's a Fuse - meaning it's written in Lua, and the source code is available for edit; in Fusion 9 it provides Edit/Reload buttons in the UI like is normal for a Fuse, but they've removed this for Blackmagic-provided Fuses in Fusion 16. But the code is still fully readable on disk, included as part of the Fusion Studio and Resolve installations.

This might make it possible to diagnose what's going wrong, by tracing through the code.

Thanks Tom to the in depth explanation

Might I suggest to the OP to change the title to a reflect the issue more clearly?
thank you

I have updated the title accordingly. While the inner workings of Fusion's node scripts are a complete mystery to me, it's good to know there's an editable source file on my drive I might be able to patch until BMD can have a look.

Does anyone know how I can ask Blackmagic about this? I only found some international phone numbers to contact.

Use the Support web form here on the website:

https://www.blackmagicdesign.com/support/contact/email

Got it, thanks!