I’m trying to have two simulated chain-like bones on a character and I noticed that when setting the two chains to simulated in the physics asset, the left chain always simulates fine, while the right one snaps to the root bone of the skeletal mesh. I have attached pictures (in the reddit link) with a testing mesh I created to show what I’m talking about.
I tried the same thing on the Unreal mannequin (using the left and right arms) and had no issues, so my assumption is that I’m doing something wrong in Blender as this has been happening with every skeletal mesh I’ve created so far.
I’ll be more than happy to provide more information or pictures, so please ask if you think you could help because I really don’t know how to solve this at the moment.
Oops, mis-spelt it in the image, but Clav_R set to kinematic and everything below set to simulated.
Every other simulated bone root below the first in the hierarchy just attaches itself to the parent. Doesnt matter how many, and can be repeated with more than just arms, as I’ve been trying to make some light jigglebones work on my character’s vest thing, if there’s something else simulating physics higher in the bone hierarchy, THAT is the only one that works correctly, every other root gets snapped backwards to the spine or its relevant parent and hangs from there instead.
Jiggle_00_00 ← this one works
-Jiggle_00_01
Jiggle_01_00 ← attaches to spine
-Jiggle_01_01
Jiggle_02_00 ← also attaches to spine
-Jiggle_02_01
Collisions work completely fine. I’ve disabled them on the relevant capsules and everything overlaps nicely on the pawn.
I found Mr. Mannequin’s tool. I’ve been trying to use it to fix this but have found no luck. Can anyone help? Am I missing something basic? Are my bones setup wrong?
October 2023 edit: If you use blender to make skeletal meshes for unreal, use Epic’s Send to Unreal tool to send it to Unreal properly. It fixes this weird issue, but still has hiccups. If you know why any of this is happening, feel free to add to this post?
Okay, quick update and bump here because I’m getting nowhere with this, and I know people stumble into these things on a 6-month basis so here’s what I’ve got on this now.
Mr. Mannequin’s tool works good for exporting. Make sure you add deforming bones to your skeleton using the tool and it works nice. If you want a fast, easy solution, I recommend using that. But that doesnt work for me, so on I go.
I’ve discovered something else; in blender specifically, if your skeleton is named ‘Armature’ then the fbx file goes “oh, wait, that’s an empty root” and just, gets rid of it, and puts whatever your root is to the actual root. Which means that, in theory, this should fix our wacky physics problem. But it doesnt, for reasons I do not fully understand.
I also tried exporting only the deforming bones. No fix there.
So, in short, simulating multiple limbs on a mesh does not work at this moment if you import a skeleton from blender. I’ll add another post onto this if I find a workaround or fix. If anyone has any pointers AT ALL, please post them.
(Deleted old Reply because it was inaccurate)
Posting here just to let anyone who runs into this issue in the future
If you want multiple limbs/Profiles to be simulated without your bones snapping to the root, you MUST do the following:
This is the critical part that took forever to figure out: In Blender, you need to make sure your units are set to metric 0.01 (if you have to change your units to 0.01 it will change the size of everything when you import, so its best to scale it back up before the following steps) , your armature and every bone is named something other than Root or Armature, and make sure all transforms have been applied to your mesh and skeleton (this is the most important part); This will most likely break any animation you have, so you will need to scale the Locations (specifically only the locations) of all keys in your animation to the scale your Armature was originally scaled to (only in the y axis)
You will have to delete your skeleton file from UE4/5 before importing the corrected skeleton and animations (you cant reimport skeletons)
When importing to UE4/5, do not import at any scale other than 1.0
You can verify this is fixed by checking all of your bones in your skeleton in editor are scaled to 1.0 (or ~.99999999 because floats)
You should be able to simulate multiple chains of bones from there
Let me know if anything is unclear, I have confirmed this time the above is the correct way to fix this issue by having a broken skeleton become a fully working multi-simulating skeleton.
Hello
I’ve been runing to this problem however the solution you gave still doesn’t fix it…
i have verified and everything is in order , but for some reason when i try to simulate physics with a kinematic bone it stops working…
if i simulate the whole skeleton everything runs fine , but if i have any kinematic bone it snaps some of its “children bones” to the root position .
Finally got this to work properly. Blender at 0.01 with correct scaling, applied transforms on meshes and armatures and all that, it works! Godda have hyuge assets in blender for it to be okay but whatever, it works!
Anyone with broken animations that stumbles across this issue, this tutorial will help you!
Still also recommend Send to Unreal for anyone, too. It helps a lot. Thank you!
