Cloth physics ignores physics body in certain situations

Development World Creation
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1

I have been trying to setup cloth physics for a character.
The auto generated physics asset is working mostly fine for that purpose, but I felt the need to add another body to it to make the cloth simulation more accurate.

However, that newly added body gets ignored by the cloth physics, at the upper part of the skirt. It only visibly works when pulling that body down to the bottom of the skirt. Other bodies, like the thigh or pelvis bodies, work just fine deforming the upper parts of the skirt.

Additionally, I noticed that when I delete both thigh bodies, that new body works as intended.
Here is a gif of the latter:
https://i.gyazo.com/2f00280a102fab1405da90b1a6456b40.mp4

Why is this? I assume it’s some limitation of bodies at work at once or something, because I see no reason why this would behave this way. And how do I configure that behavior? Or where is more information about that? I haven’t seen anything about this in the docs.

2

Hi, this is a common problem. You are currently trying to add a new capsule collision which supports physics but it has nothing to do with the bones or body constraints. For some reason, UE4 needs bone constraints information in capsule collision to communicate with the cloth physic. You can see this clearly in the graph.

There are a few steps to do so. This solution also has been explained in an Unreal Livestream on Youtube.

Here, take a look at the Livestream which explains how the capsule collision should be created.

Hope it helps… :slight_smile:

Youtube Livestream

3

Thanks, I’ll take a look.
This body is attached to a bone though, and I added body constraints as well. I just did all I could to make the new body the same as the other bodies. It’s just that number of bodies seems to be a problem for cloth physics (for whatever reason). Others have found this out, I tried it out as well with a separate physics asset that has less bodies that are more relevant to the skirt, et voilà, it worked.

4

There seems to be a maximum body limit for cloth physics. So later added bodies dont end up interacting with it. I dont know if there is a way to disable some bodies for cloth, or just change the order of them to prioritize certain bones, but it doesnt look like it. I just had to delete my finger bodies to reduce the body amount and it worked