Edge Physics/Collision bug

Hello,

I am having issues getting a ball to roll smoothly on other objects.

See video: UE4 Physics/Collision Bug - YouTube

The ball rolls fine, but as it gets speed, it seems to hitch/glitch on the geometry. Sometimes it can even completely stop the ball from rolling all together. In the video, each time you hear the bump sound is when it’s hitting(what I think) are the edges of the geometry, and this happens even on perfectly flat surfaces.

Here is the imported .fbx file:
https://drive.google.com/file/d/12KduLoYUu6F6UX3cN0bCEVUO5Nd5xLkE/view?usp=sharing

In Blender the geometry is perfectly smoothed, and there are no hidden polygons inside of the object, so I’m unsure why the physics are catching on what seems like the edges of polygons.

CCD is enabled.

PCM is enabled.

Thanks.

It is already is a simplified sphere collision. What I’m having issues with is; some times(randomly), the ball will hit an edge of a poly and bounce. This means unless every part of a map is flat and has no edges, the ball will randomly bounce. It goes over other edges in objects smoothly in most cases, but the random bounces are an issue.

See this: "Perfect" sphere collisions causing bouncing - World Creation - Unreal Engine Forums

Already tried. Seems to make it worse with PCM disabled.

I believe I found the issue. I’m gonna post it as a separate answer and delete this one.

Hi,

The rolling ball instability that you’re experiencing is a common issue with physics engines. In your case, it’s probably due to the default settings of Unreal Physics Engine and your surface mesh’ quad size (they’re probably too small). You need to tune some parameters of the Physics Engine to reduce such issues. In project settings, start by lowering these values: Min Contact Offset, Max Contact Offset. You can also try increasing Contact Offset Multiplier. Note that changing these values will increase the stability but at a cost of performance!

Hope this helps!

Min Contact Offset and Max Contact Offset are set as low as they can possibly go, and Contact offset from 1, 100, to even 1000+ has no affect on it.

I’d also like to point out that its doing this even on flat surfaces.

Thanks.

I’m sorry that your issue has not been fixed yet. I suggest you bump this post again or post a new one here or in the forums with a “bug report” tag so that Epic staff can take a look it. You can also report this directly to Epic and provide them with materials and exact steps so that they can reproduce this on their own machines.

Have you found any solution? I am having the same issue.

Sorry :\ The only way to fix it is to create your own custom physics.

k. In the meanwhile I have issued an official bug-report which is confirmed by Epic. View and vote for it here: Unreal Engine Issues and Bug Tracker (UE-74451)

Bug is reported and confirmed by Epic. Track the issue and vote for it here: