Physics simulated actor gets stuck in other actors it needs to overlap

Development World Creation
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1

Repro steps:

Create a new project using Side Scroller Template (just for convenience).

Create a new blueprint class TestActor using Actor as parent.

Add a Box Collision component to the TestActor, make it a root component.

Uncheck Hidden in Game so we can actually see it.

Check Simulate Physics.

Set up a custom Collision Preset:

  • Collision Enabled: Query and Physics
  • Object Type: WorldDynamic
  • Blocks WorldStatic
  • Ignores WorldDynamic
  • Overlaps Pawn

Spawn and throw TestActors at the player pawn at some random angles using AddImpulse.

Result:

Sometimes TestActors get stuck in the player pawn. It looks like this: Dropbox - File Deleted

My test project can be downloaded here (Use E button to spawn TestActors):

2

Hey koloden,

Thank you for the test project. I’m still looking into this but so far I have noticed if you disable Generate Overlap Events on either the player capsule or the box collision, the issue doesn’t occur. Depending on what you are doing, that might be a decent workaround for the time being.

3

Hi,

I also noticed this but I need them to generate events in my project. I came up with another workaround: to use two separate collisions in my TestActor. The first one is PhysicsOnly / Block WorldStatic / Ignore everything else, and the other one is QueryOnly / Overlap Pawn / Ignore everything else. Maybe there is a better way to achieve such behavior?

4

Yeah, this is probably the best way to handle it in the meantime. If and when this issue is fixed, it would be pretty easy to change over.

5

Thanks, so I’ll stick with this solution for the time being. Is there some issue in the tracker I can monitor?

6

Yes, here is the link to the public version so you can keep track of it JIRA UE-53227 and our devs will be investigating further.

Thank you for the report,
-TJ

7

Awesome, thanks.

8

Why was this marked as “wontfix”?

9

How is this a “won’t fix” ? You have a bug in your collision system and you just won’t do anything about it?
Idk maybe you could at least set a warning in the engine so that people don’t waste 3 ■■■■■■■ hours of their time on something that should work but doesn’t for no apparent reason?

10

I’m working with UE4 4.26.2 and seem to have encountered a similar issue. Because OP’s dropbox links are no longer working I have no idea if this is in fact the same issue

I have an actor with a static mesh as its root and a sphere collision as a child being thrown using addImpulse by the player pawn. In my instance, the issue occurs when the object is thrown at such and angle where the object is spawned inside of the player pawn’s capsule collision.

Occasionally, the object seems to get ‘stuck’ on the edge of the capsule.

The Static Mesh is set to type PhysicsBody with generate overlap events ticked on. It has a custom collision Pawn set to Overlap, and everything else set to Block.

The Sphere Collision is also of type PhysicsBody and has everything set to Overlap.

I’ve fixed this issue by following OP’s suggested workaround. I’ve changed the Static Mesh’s Pawn collision channel to Ignore and changed all channels in the Sphere Collision’s physics to ignore while keeping Pawn set to Overlap.