How does the Latissimus Dorsi muscle move?

Unity Engine
1

This isn’t really related to unity exactly, but it is related to animation.

I’m re-rigging a character for unity’s humanoid mecanim rig, which doesn’t have a lat dorsi bone, of course. The original rig for my character did, and i may have accidentally deleted that rigging information.

No matter. I’m re rigging it to fit the bones i do have. Primarily shoulder, and upper arm. But i’m not too familiar with this muscle, since most normal humans don’t have much of it. My character is a powerlifting super mutant of sorts, with far more defined muscles, so it’s more of an issue here.

anyways, i’d like some advice on exactly how the latissimus dorsi muscles move. In what positions they contract or extend. Maybe a visual/video guide if you know of such a thing? And maybe some advice on how to map that motion basically to a shoulder, arm, and a couple of spine bones

2

I’m just getting started myself with rigging characters in Unity specifically, but I have studied figure drawing and animation for several years, so I can provide a more generalized answer to the first part of your question.

Basically the “lats” are fairly flat sheets of muscle fiber that wrap around either side of the mid-torso, like a sheath, and taper upward to the points where they attach under the arms.

See this diagram:

As you can read on that page, the “lat” plays a role in a wide range of motions of the arm, so it stretches and contracts in many different ways depending on whether the person is raising their arm to the front or to the side, rotating it medially to the front or to the back, pulling down on a weight (as in a “lat pulldown”), but the contraction or stretching of that muscle is usually going to be pretty subtle as you said.

Don’t be afraid to get up and move around and see what it feels like. Your own body is very often the best source of information available to you as an animator when trying to simulate a human figure in motion, because not only can you observe yourself in a mirror or on video, but you can actually feel the movement of the specific muscle you’re interested in.

As far as research material for a super-mutant muscle-bound character, my suggestion would be to search YouTube for shots of body builders or weight lifters working out in order to get a sense of how those muscles contract and stretch as they move their arms or pull weights downward.

It’s also always worth asking: how much of these efforts will be apparent enough to matter to the players of your game? If the payoff in the end is going to be worth the effort to rig every muscle, then have at it, but at some point the quest for realism has diminishing returns. A wise instructor of mine in animation school had the motto, “If it looks right, it is right.” In other words, don’t let yourself get bogged down by trying to simulate reality down the Nth degree, and know when enough is really enough.

I know this doesn’t exactly solve your problem, but hope it helps somewhat as a starting point for further research at least. Good luck!

1 Like