I have an object with an armature modifier (although this would apply to any modifier that deforms the mesh). I want to Project from View unwrap to get a UV map for one pose, then change the pose and Project from View again for another UV map. This doesn't seem to be possible because Project form View apparently only works with the base unmodified mesh. I tried using the on cage and edit mode options on the armature modifier, but it still uses the base mesh.
2 Answers
I found a solution if anyone sees/needs this, you can make duplicates of the object, pose them, apply the armature modifier, then do a Project from View unwrap for both of them. Then use Transfer UV Maps(Ctrl + L) to transfer them back to the original mesh.
(https://docs.blender.org/manual/en/2.80/editors/uv/layout_management.html)
Create a pose.
"Duplicate" the Armature Modifier from the down arrow menu over in the Modifier Tab (in older versions, it's a "Copy" button).
Save your pose as a "Shape Key" with Armature > Save as Shape Key (in the duplicate Armature Modifier).
Activate the "Shape Key".
Unwrap your mesh.