Join as shape key is Y mirroring the donor

Support Technical Support
1

I’m trying to join these two meshes as shape keys, and they line up when they’re separate, but after I join them the resulting shape key is Y-axis mirroring itself. (I checked by toggling the value up and down, and it is a Y mirror, not a 180 rotation.)

Key flipping 1
Key flipping 11000×755 156 KB

Key flipping 2
Key flipping 21000×755 149 KB

I haven’t run into this before, and when I thought maybe I could just correct it by going into edit mode for that key and doing a Mesh>Mirror>Y Global, that made it just completely vanish off the stage (I scrolled as far away as I could and it appeared completely empty).

I’m using Blender 3.6; the figure was rigged in Daz and bridged over.

2

So maybe one of the meshes did have a Y-scale of -1.0 in the first place ?? ( or inverted normal…)

3

So how do I fix that? Either fixing the mesh before I join them or making it stop vanishing when I try to do it in edit mode?

4

My suggestion was considering the possibility that something was wrong before the join… so… yes… have a look at it before joining.