UVs destroyed after ZRemesh despite Paste UVs

[AC2015]

Hello!

I want to decimate the model of a flower.
It’s already UVed.
So I first click “Copy UVs”.
Then I use ZRemesher to bring the tri count down.
Then I click “Paste UVs”.

Now when I click “Morph UV”, the UV map looks really strange / destroyed / broken.

What did I miss?

I’ve attached a screenshot.

Perhaps I should explain what I need to do:

I have duplicated a flower subtool many times, and I spread it over a hat as an ornament.
I rotated the duplicates, and I scaled them so that one wouldn’t notice that it’s the same flower.

I would like to export all flowers together as “ornament.obj”, so I would need to merge them.

I need to export a high poly model and a lo poly model of it.

The high poly model of the flower subtool is already UVed.

My plan was to

1. merge the high poly flowers down having “UV” activated in the Merge panel, then export them as “ornament_hi.obj”.

2. copy the hi poly UV of one flower, then zRemesh each flower and paste the hi poly UV back onto the zRemeshed lo poly flowers.

I’m not sure if that’s a good / valid workflow…?

The reprojection of the hi poly UV onto the lo poly subtool resulted in this strange UV map.

Attachments

[Cryrid]

You can’t copy and paste UVs when the topology changes.

All copying and pasting does is copy the coordinates based on vertex order, not position. “Vertex 001 has this UV coordinate, vertex 002 has this UV coordinate, Vertex 003 has this UV coordinate…” and so on. If you do anything to change the vertex order (adding a vertex, removing a vertex, and most certainly replacing all of them with Zremesher) then you’re going to have a complete mismatch between what you’re copying and what you’re trying to paste to.
On your first mesh Vertex 001 might be on a nose. After ZRemeshing the model Vertex 001 might be on a toe. Copying and pasting won’t care.

[AC2015]

Thank you very much for this explanation!

Decimation Master with Keep UVs achieved what I needed.