# Rolling physics ball changes direction

**URL:** <https://forums.unrealengine.com/t/rolling-physics-ball-changes-direction/486480>\
**Category:** World Creation\
**Tags:** bug, sphere-collision, rolling-ball, unreal-engine, Physics, question\
**Created:** [July 21, 2021, 5:55pm UTC](https://forums.unrealengine.com/t/rolling-physics-ball-changes-direction/486480 "2021-07-21T17:55:25Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Acriax](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/acriax/32/472400_2.png) [@Acriax](https://forums.unrealengine.com/u/Acriax)\
**Post date:** [July 21, 2021, 5:55pm UTC](https://forums.unrealengine.com/t/rolling-physics-ball-changes-direction/486480/1 "2021-07-21T17:55:25Z")

</div>

I’ve been having an issue for a while now that I cannot pin down.

For some reason, my physics ball actor randomly changes direction without any additional input upon it. All I do is give it an initial push, and set a timer to draw a debug arrow for the velocity vector. The ball has no linear dampening. When all goes well, it rolls to the end of the arrow, and another should spawn with the same direction and essentially same size (there is a minor amount of friction I believe.)

But as you can see from this picture, sometimes, the ball suddenly decides to move off in another direction and with a different speed. Sometimes it’s subtle, sometimes it’s abrupt like here.

I’ve set the collision for the floor beneath to only be a single box primitive, and the collision for the sphere is a sphere primitive of course. The sphere has the following setup:

```
 - Scene Component
     - Sphere Mesh (Simulates physics)
          - Point Light Component

```

I don’t particularly care about this sphere itself, it’s just a test, but this kind of thing keeps happening. Why does the UE4 physics behave this way and how can I solve it?

 ![](https://d3kjluh73b9h9o.cloudfront.net/original/4X/c/f/2/cf2ad0bb0c7ea45dc5bd0b5df2a49127ee17d61b.png)

My project physics settings:

 ![](https://d3kjluh73b9h9o.cloudfront.net/original/4X/9/c/a/9ca904c21aa371ee5f11e7b5b1615d5e58a68281.png)

---

<div class="post-metadata">

**Author:** ![Everynone](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/everynone/32/1135017_2.png) [@Everynone](https://forums.unrealengine.com/u/Everynone)\
**Post date:** [July 21, 2021, 6:31pm UTC](https://forums.unrealengine.com/t/rolling-physics-ball-changes-direction/486480/2 "2021-07-21T18:31:40Z")

</div>

Could you ensure the component simulating physics _is_ the root of the actor (drag the mesh onto the root). Does it help at all?

Also, are you using any plugins?

---

<div class="post-metadata">

**Author:** ![Acriax](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/acriax/32/472400_2.png) [@Acriax](https://forums.unrealengine.com/u/Acriax)\
**Post date:** [July 21, 2021, 7:48pm UTC](https://forums.unrealengine.com/t/rolling-physics-ball-changes-direction/486480/3 "2021-07-21T19:48:43Z")

</div>

Thank you, though it did not help. I think I found the culprit however, in a physics volume that was encompassing the scene. Removing it made the issue go away.