Question How do you generate contacts in DOTS Physics?

It is mentioned here: https://docs.unity3d.com/Packages/com.unity.physics@0.0/manual/simulation_modification.html that contacts can be generated in the Unity.Physics.SimulationCallbacks.Phase.PostCreateContacts phase.
How is this done?

I am trying to create my own wheel collider and I thought it would be a better idea to generate contacts than apply impulses like the samples

 

Hey, adding contacts is not currently supported, sorry about that, documentation is a bit out of date. We are trying to think of the best way to implement this, but unfortunately it has a lot of implications to the rest of the physics pipeline and we need to be really careful.

 

https://docs.unity3d.com/Packages/com.unity.physics@0.3/manual/simulation_modification.html This is the documentation for the latest version of the physics package. Which version are you using?

 

I can imagine it does
It opens up for quite amazing stuff though so I'm really rooting for you! (not that it necessarily helps you much but still... )

I realize now I was looking at some old documentation yes...

So I guess at this time it would be quite hard to implement a wheel collider then, right? My idea was that I would create a wheel collider that generates contacts so that the solver can handle them rather than using raycasts as in the samples. Otherwise I guess there will always be pretty strange behaviour when the static friction should make objects come to rest, right? Or am I missing some way to approach this?

 

Thanks for rooting, it certainly helps!

Regarding the wheel collider, I guess there is no easy way to do it with current options.

Assuming you want to do a query (ray cast or collider cast) and then let some solver take care of it, maybe (just maybe) you can take a look at the SimplexSolver. Character controller does something similar - query the world, collect hits and convert them to constraints (the way it likes it), and calls SimplexSolver.Solve() to get a new velocity. Not sure if that's enough, could be. It definitely doesn't need to use impulse applying. Let me know if it feels right!

In the meantime, I will (once again) think about adding the contacts to the pipeline.

 

Ok sounds like a good idea. Maybe I will just wait until out of preview instead, this is not a critical task at all. Just playing around a bit with physics + netcode to get a hang of how things will work in the future.

I really like where all of this is going, keep up the good work!

 

Also, thanks for taking the time to answer!