I’ve tried to add some breast physics to one of my metahumans.
I’m using it in a short movie where 90% of the time, the physics I’ve added work perfectly.
In some shots, the breasts are totally out of control and fly everywhere. It seems like unreal is searching for how to apply physics. After a while, it seems to find a way to do it, and it stabilizes.
Here’s a movie of the problem:
I’ve searched online and found proposals for a solution with rigid bodies, which didn’t help.
It seems like the physics asset is colliding with something else and launches the body away.
I’ve removed the physic-bodies around the arms or removed other characters who stand very close to see if that helps, but that didn’t solve my problem.
I’ve found something,
if I make spine_05 larger (the shape / bone onto which the breasts are attached), in such way that both breasts are inside, it acts strange for a little second, and afterward it stabilizes.
I’ve reduced the problem by setting the strength of the linear motor to a ridiculously big number (90000).
Now the breasts find their place after 10 frames…
I have the feeling this isn’t a real solution. I “limit” an error which shouldn’t happen at first.
Secondly, the problem keeps on occurring for freshly spawned metahumans as they don’t have warmup frames.
I thought when following this thread I would end up with a solution:
I thought my problem would be related to the framerates,
I started a whole new project and reimported my mocap (first 2 clips). they were recorded at 125fps
Afterward, I retargeted and imported 2 Mixamo clips at 30fps (the last 3 clips).
I’ve put the sequencer to 30fps, instead of the 25fps.
And did a render with, and without the changed project settings as proposed in this thread.
Unfortunately, both renders behave a bit differently, but the change isn’t incredible…
here you can see a comparison video I’ve made:
but unfortunately, this isn’t a solution too…
It looks a bit better, but in the beginning, it’s still flying everywhere…
Out of curiosity are your characters to scale? For instance is the female character between 150 → 180 units tall? Could the characters be at a scale that is off by a factor of 10 causing physics to act strange?
I’ve found the solution.
When spawning metahumans, they’re spawned onto a position of 0, 0 ,0.
In the sequencer, I’ve given them another position. So the metahuman is spawned onto “0”, and “thrown” to its new position in 1 frame.
The breasts and physics are still on 0 when the position is renewed, and “thrown” to its new position. You can see the same happening with the shoes if you slow down the render and watch it frame per frame.
Delaying the physics was the solution then, and I’ve added this to the “event beginplay” blueprint. Maybe there are more elegant solutions:
For one reason or another, my problems started all over again in Unreal 5.4, when I updated my project from 5.2 to 5.4
I got better results by rechecking the physics settings in the project settings.
There, I’ve added again substepping, and the numbers I don’t understand as described above.
But the problem is still happening…
