Actor disappears on simulate physics

I was just playing around with ragdoll physics and come across this:

The exact same thing happened inside the physics asset itself.

some more images to support that I hope it’s not just me.

If someone could shed any light on this it would be great!

Thanks in advance guys!

Hi Annunaki69,

Have you created a Physics Asset for your skeletal mesh yet? Make sure you have done so and also that the skeletal mesh is set to use it under the Physics options in the Detail panel.

Here is some more info on Physics Assets.

If it all checks out and you are using a Physics Asset, please let me know and we can continue investigating.



Hi TJ,

Thanks for the reply. I’ve just checked everything there is a physics asset and it is definitely set to be used.
I’ve had a look at the link you posted as well and there’s nothing that jumps out at me.


I’m assuming you are only seeing this with your custom skeletal character. Would you be willing to post a small test project or the .uassets? You can send me a download link by PM over the Forums if you prefer.

link text

There you are TJ if you can have a look you might see something I missed!

Thanks again!

I had a similar issue to this that only affected actors with physics enabled.
There are a couple of things you should check:

  1. Make sure your actor’s location is not below the WorldSettings->KillZ threshold.
  2. Try disabling the WorldSettings->EnableWorldBoundsChecks (this was my problem).

Both settings are in the World Settings tab on the level editor. You will need to open the hidden section to find the EnableWorldBoundsChecks flag.

Good luck!

Okay, so the skeletal mesh isn’t disappearing. The physics asset is going crazy and it’s being thrown right at play or simulate. Go into the Stickman_Physics asset and press simulate in the PhAT editor; you will see it disappears there as well.

I believe this is caused by the lack of a Root bone on your skeletal asset. The engine requires it in order to properly generate a physics asset. Try adding a Root bone to the character before you import and see if that clears up the issue.

The other option would be to delete all of the physics constraints in the PhAT editor and double-click each bone in the Hierarchy panel to create them manually. That also seems to fix the issue.

Let me know if that works for you.

Hi TJ,
Deleting all the physics constraints worked like a charm!

Thanks for the save!

antsonthetree, Thanks for your comment! It helped solve a similar problem. I could pick up the BP_PickupCube (from VR) but when I’d release it, it would disappear. It turned out that the cube was initially placed below the kill zone but attached to another (moving) structure, when picking up the cube it would attach to the hand but when the cube was completely detached from everything (at release) it would disappear because it was below the kill zone.

For others: To fix - go to “world settings” → world → “kill z” and set the value below your objects.