I am really stuck. I used Plask, an AI mocap tool to capture some movement from video, and I managed to apply that movement to a character that I made in Blender. When I download the animation out of Plask, the mesh looks different (for example it's been triangulated and the normals are weird, also the rest pose is no longer a T-Pose), so I thought I'd retarget the animated armature from the downloaded fbx to control my original T-Pose armature (which is parented to my original nice and clean mesh).
I tried both the Retarget Helper Addon and the Game Rig Tools Addon but in either case, retargeting twists my original mesh in weird ways. The two armatures are the same in terms of bone structure and naming convention.
Without retargeting, each armature deforms its respective mesh just fine. I've played with the roll settings on different bones but that didn't help. I just cannot work out why the mesh gets twisted. Any ideas?
Ultimately, retargeting will need to be the way to go, because then I can put different textures on the character and easily mix & match movement sequences to character versions.