Creating multiple instances of imported object causes mesh artifacts

Styl1sh

Found something odd by accident. If you import an .obj made in blender's scultping tool, create a new appendage model group, and start placing shapes, you'll notice that:

• First two shapes get placed correctly
• Placing a third shape breaks the mesh of the 2nd shape - some of the vertices go back into 1st shape
• Trying to place additional instances doesn't create new shapes - only more of the other object's vertices start merging with the first shape.

This only happens within a single appendage group. You can create a new group and place 1-2 shapes with no issues, but the moment a 3rd instance is added within a group, meshes start to break.
There's nothing special in the log: https://pastebin.com/rZ9Kjg6Z
Since this is not an issue with in-built claw shape, could the culprit be on the blender's side? The imported meshes have high poly count, would it be a feasible explanation that the group is hitting vertice limits, and it's just folding in on itself?

Styl1sh

Adding a link to the shapes I've tested on:
https://drive.google.com/drive/folders/1CUwZuIlpY_EJf9bj4gCoo2t947nT9QAj?usp=sharing

Styl1sh

The object complexity seems to be the key - I've simplified the object significantly, and now I can place up to 15 instances without the issue.

odes

I think a mesh in Unity can only have 64k verts.

Those obj files are crazy. For comparison, our character has ~22k verts in engine. Your single claw has nearly 24k verts. That's insane. There's no reason for an appendage to have that amount of verts. They should be in the low hundreds.

We should probably implement some tool that gives the user feedback about things such as this.

You should look into retopology. There are free and open source tools, such as this one:
https://github.com/wjakob/instant-meshes



Download (linked on github page too)
https://instant-meshes.s3.eu-central-1.amazonaws.com/Release/instant-meshes-windows.zip

Styl1sh

Blender's clay sculpting is very generous with vertices. I wish regular modeling was at least somewhat intuitive..

odes

You don't need to do any regular modelling at all. You can literally just load in your high poly file into that retopology tool, and get a low poly mesh from it.

Styl1sh

I'll have to stick with blender's decimation modifier - this tool does not retain enough details of original model to make it usable.
Thanks you about the information about retopology, I'll definitely look it up.