I wish I knew the word, it would help me find the solution but several guesses like "physics" or "occlusion" or pass through etc etc took me down many false paths.

In a nutshell   What stops body parts from passing through each other ?
It sounded like a simple thing to find, but I still failed. My eyes hurt now after hours and hours of searching and experimenting.

I'm learning this as I go, just for fun, so I apologies if I missed it in the basic tutorials.

I tried to take a character (Mason) place one hand on his chest, and place the other hand on top, its fine as long as nothing moves.
Attempt to make him breath move his head etc, results in fingers passing through the back of the opposite hand, or hands passing through the chest.

I played around with "Hand Contact" "reach target" and "Collision Shape" couldn't solve it.

Appreciate if someone can point me in the right direction.

Thanks Alan

Currently there is no collision detection that works between body parts, such as there is for clothing. So you will have to correct manually using keyframes.

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Thanks for that, seems an obvious omission. Would it be possible to sandwich a very small  invisible object between them and use that to stop it happening or am I looking for a silver bullet that doesn't exist.

Thought about gloves, make them invisible, but I guess it wouldn't work as the arm passes through the shirt.

Thanks