Skeletal Mesh & Physics Physics Assets wrong initial pose

Development Character & Animation
1

Hi

I am experimenting with a very simple bike rig test that I have prepared in blender as follows:

bikeBlender.png
bikeBlender.png1115×863 46.6 KB

I then imported it as a Skeletal Mesh and added the following physics asset:

bikePhysAssetUE.png
bikePhysAssetUE.png938×579 96.3 KB

The wheels are hinges and the simulation behaves as expected.

But when I drag the physics asset to the scene however. It looks like this: (the collision shapes are configured to not collide with one another)

bikePhysSceneWrong.png
bikePhysSceneWrong.png990×759 312 KB

It has to do something with the pysics because when the simulate physics checkbox is off, the bike looks normal again.

When I run the game though all the parts pop back into place immediately and look again as expected:

bikePhysSceneRunning.png

Is there something I should be aware of that can cause this behaviour? It looks like some sort of collision is happening within the object or some sort of offset?

thanks

2

You need to have all of your joints be Z-Up (which I think you are using Blender, so they will be) BUT you are ‘facing’ down Y, thats a no-go for Skeletal and UE4, redo it all with the bike ‘facing’ positive X and have the joints facing that way too.

3

Hi

Thanks for your quick reply. I fixed the orientation of the model but I still have the same problem. I think the thing is that all the bones have an offset to their parent and the physics somehow moves all the bones to the objects origin. But as soon as the simulation steps they jump to the position they are supposed to be.

4

As a quick workaround I can enable the physics when the level starts. This seems to do the trick.