Resolved Creating and destroing physics joints during runtime.

Recently I've been working on a simulation where I need to be able to dynamically create and destroy joints between multiple objects during runtime. I've looked around and I've tried to find a way to create joints in this way. However, the only thing I've come across is the physics examples by unity, which use an authoring component and the GameObjectConversionSystem, which as far as I can tell, only runs at the start of the simulation, and has to at that as that is the only time when the DstEntityManager is available, which is used by the EndJointConversionSystem in the CreateJointEntities method. So I'm a little bit stumped, I'm not really sure how else to create the joints other than what is shown in those examples. Any sort of help or advice would be greatly appreciated.

I'm using unity version 2020.2.1f1.

 

Basically, in order to create a joint you need to create an Entity with PhysicsConstrainedBodyPair and PhysicsJoint components, so it can be done at runtime. PhysicsJoint.Create*() and SceneCreationSystem<T>.CreateJoint() can help with that. You can find some examples in UnityPhysicsSamples\Assets\Demos\4. Joints\Scripts\RagdollDemo.cs, RagdollDemoSystem.CreateRagdoll() .

Side note about joint lifecycle: If you delete a body Entity that takes part in a joint, you should make sure to delete the joint Entity as well (it won't happen automatically).

This should help you get started, but please let me know if you need any further help down the line.

 

Ohhh, okay thank you that makes a lot more sense.