I’ve been playing around with the physical animation component and I’ve come across some weird behaviour. When I set a skeletal mesh to simulate physics, and local simulation is checked, the bones try to match the position of the animation, but at a strange angle. After trying this out on a few different projects, and encountering the same behaviour on them all I’m reaching the conclusion that this might be a bug in the physical animation component.
You can see the behaviour here: Imgur: The magic of the Internet
And here’s my graph (the bone variable is set to pelvis):
As far as I understand this should cause the entire skeletal mesh to use physics, but should try to constrain to the orientation of the animation with a strength of 1000. When this number is cranked up to 99999 it’s very clear that the animation is being constrained to, but at an undesirable angle: Imgur: The magic of the Internet
This is using the default third person project with the only addition being the small graph in the image and a physical animation component. I’ve tried it in a few projects, including the content examples project and I’ve had the same results. Oddly, if I rotate the skeletal mesh to the angle it constrains to when physics is applied, the skeletal mesh doesn’t exhibit any additional rotation: Imgur: The magic of the Internet
Thanks!
Hey CapableWizard,
Have you set the collision up to ignore your capsule and vice versa?
Hi ,
I don’t think collisions are the issue, even with the capsule set to no collision the behaviour is the same.
I’ve also tried the skeletal mesh as part of an actor with no collisions (not a character) and the same weirdness occurs.
There has to be something else going on in your blueprint that is different. I just set up the exact same BP on the Third Person Character BP. I adjusted the collision settings to make it work better, but even with defaults it wasn’t turning to the side.
Can you set up a sample project and send it to me? Since you’re using template content, you can upload to a cloud service and send a download link here.
I’ve gone back and had another look at the default projects and I’ve realised that I have actually changed the collision settings from the default “CharacterMesh” preset. Having done a bit more investigation it appears that setting the collision enabled drop down to “Physics Only” or “Collision Enabled” triggers the odd rotation. Leaving collision off or query only does fix the rotation issue, but also disables collision (and disables any physical animation components). It could be a total lack of understanding on my part but I would have thought the physical animation component relies on the collisions being enabled in order to function properly?
I’ve attached a copy of a fresh project anyway, the skeletal mesh is set as a physics actor preset and the capsule collider is a pawn with physics actors set to ignore 
https://drive.google.com/file/d/0B7IpavEIjOtuMGVlMHZKQXdTVk0/view?usp=sharing
Hey Capablewizard,
This appears to be a direct result of your extremely high orientation strength. If you lower it in increments, you’ll start to see that the mesh tends to fall to one side or the other. The high orientation strength seems to make this go nuts.
