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Unity Unity.Physics 0.5.1 breaks through!

Discussion in 'DOTS Physics' started by CookieSalad, Sep 18, 2020.

  1. CookieSalad

    CookieSalad

    Unity Technologies

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    Hey everyone! For your consideration, we present Unity.Physics 0.5.0-preview.1! This release houses one really important change for Physics, so please be sure to look through the release notes before upgrading. We have also bumped up the minimum Unity version to 2020.1.0f1. Here are the release highlights:
    • Attention! Old serialized data from releases before 0.4.0 will be removed in this release. If upgrading from an older release, upgrade to 0.4.0 first and run the upgrade utility (Window -> DOTS -> Physics -> Upgrade Data).
    • Physics now updates in the FixedStepSimulationSystemGroup (see this post). This means that Physics will now be able to update completely independent of the rendering frame rate. Time to flex those GPUs!
    • Physics bodies can now be smoothed if the Physics step and Rendering steps are out of sync. New options have been added to PhysicsBodyAuthoring to support this functionality, similar to the interpolation option on classic Rigidbody components.
    • Debug Draw rendering is now significantly faster and should be able to handle much more complicated scenes with ease.
    • Known issue: the Debug Display can flicker on and off when using the default “catch up” behavior of FixedStepSimulationSystemGroup, which can present problems when stepping one frame at a time.
    • Various bug fixes!
    • Misc performance improvements!
    For more detailed changes, have a look at the change log.

    The Physics Samples project has had its scenes updated to support the fixed time step approach.

    Havok.Physics 0.4.0-preview
    that is compatible with this release of Unity Physics is also out now!

    It has been the case for the past Unity.Physics releases that they were pretty big in scope and this one is no different. We’ve taken care to reduce impact to your projects as much as possible, but some inconveniences might have slipped under the radar. If you encounter them, please don’t hesitate to report them in this thread or using the Bug Reporter tool! We will be planning a patch release in the coming weeks to address some of the known issues and further spruce up some of the demos.
     
    Last edited: Sep 23, 2020
  2. Onigiri

    Onigiri

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    Samples doesnt work for me
     
  3. petarmHavok

    petarmHavok

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    When did you try the samples? They were updated just recently, please make sure you got the latest version.
     
  4. Onigiri

    Onigiri

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    I'm on the latest version of samples and 2020.1.2f1 version of editor.
    Edit: Restarting editor fixed the issue
     
    Last edited: Sep 18, 2020
    Kmsxkuse and petarmHavok like this.
  5. snacktime

    snacktime

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    Debug draw sounds really nice.

    Interpolation is sort of what I guessed it would be. We rolled our own which we will stick with some notes on what I think is problematic with the built in solution.

    We have a fairly complex interpolation setup. Moving platforms where other bodies have to move relative to them but in different ways. Characters that move independently, bodies connected via joints, some that move relative to but don't use joints.

    We also have to access interpolated positions long before where physics does interpolation. Interpolating at end of frame leaves very little time to do anything.

    We chose interpolate early right after physics runs. So that everything else has access to interpolated positions. But we also have an InterpolatedBody abstraction that physics logic has to write to. This means it's not automatic but it's also inherently more flexible. Like moving B relative to the interpolated position of A is easy. We don't have to be a frame behind on anything either. The cost is everything has to reason about interpolation and whether it is working with an interpolated position or not.

    I feel like there is a better middle ground. Our solution is overkill for a lot of trivial cases. But complex cases using the built in flow best case force unnecessary compromises like being a frame behind.
     
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  6. snacktime

    snacktime

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    So why do integrity checks include kinematic bodies? The caveats for updating between build and step don't always apply. This sort of screwed us and unnecessarily it seems. How badly I'm not sure yet as I'm going to have to dedicate a significant block of time before upgrading.
     
  7. spirachi77

    spirachi77

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    Is there a way to both have fixed physics updates and the ability rollback and re-simulate physics worlds? If so, how? I want to develop a game with rollback and this would be very helpful.
     
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  8. petarmHavok

    petarmHavok

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    Integrity checks are there to help you, they are not mandatory and can be easily turned off.

    However, some of the checks do apply for all bodies, since the problems you can see are really serious. For example, imagine adding a component data to your kinematic body. And sadly, in some case, it can get moved to a new chunk. Then ExportPhysicsWorld comes, presuming an order of entities from when the BuildPhysicsWorld ran, and writes back totally wrong data to a bunch of entities.

    So bottom line is, you need to be careful. Integrity checks are there to let you know what can happen, and it's in your best interest to be extremely careful about the things you are doing during the step.
     
  9. petarmHavok

    petarmHavok

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    We will be providing a rollback example, we just didn't get to it yet.

    In short, if you need to do rollback, you need to take control of the step, not let StepPhysicsWorld take care of it. What you need is the utility to copy the ECS data at certain points, and then when you decide to roll back, you copy over the frame ECS data and execute the build-step-export combination a number of times.
     
  10. snacktime

    snacktime

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    Ok good to know turning them off won't break stuff.

    FYI why we were doing that is because if you run before BuildPhysicsWorld and access bodies you have to just use Run(). After export and it's a frame late. And the use case was kinematic bodies we move directly so sort of an easy choice.

    On that note what do you think about cloning the Collision world post export as a way around the whole bodies reset issue? Make a fast copy of the bodies clone the broadphase.
     
  11. petarmHavok

    petarmHavok

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    As a temporary thing I say why not. But I'll work on fixing the issue with the BuildPhysicsWorld you are seeing to provide a proper fix for this.
     
  12. Gen_Scorpius

    Gen_Scorpius

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    It seems that you have forgotten to generate the browser documentation entry for physics 0.5.0-preview.1. In the package manager it only links to the local md files of the package.
     
  13. CookieSalad

    CookieSalad

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    Our documentation team is still in the process of verifying it. We'll update the main post with a link to the docs once they go live.

    Edit: Here it is!
     
    Last edited: Sep 23, 2020
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  14. Extrys

    Extrys

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    Any news on Joint Motors?
     
  15. No3371

    No3371

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    Gosh, Burst was turned off.
    Gotta always checks it first.....

    I just downloaded the updated ECS example repo and it is doing weirdly slow, for instance the ragdoll example starts at 100+ fps, then quickly drops, eventually stays at 2.5 fps when all the ragdolls lies still on the stair.

    The profiler says it's the EndFixedStepSimulationEntityCommandBufferSystem waiting for several physics jobs to complete.
    upload_2020-9-24_18-10-14.png

    Other demos I tried (Planet, ForceField) are also very slow. I thought I was overestimating the power of the Physics package, but got suspicious.

    The PC spec is Win10 pro on i7-9700 + 32GB Ram + GTX1080 4G
     
    Last edited: Sep 24, 2020
  16. WildMaN

    WildMaN

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    Updating to 0.5, I noticed that two colliding dynamic bodies manually stripped of PhysicsVelocity no longer produce a colliding bodypair for IBodyPairsJob. Sounds like some internal optimization, though it's still a perfectly valid use case, at least for me. Wonder whether it's intended or not.
     
  17. petarmHavok

    petarmHavok

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    Are you sure this started in 0.5 (you upgraded from 0.4.1?)?

    There is nothing in this release that relates to this, so maybe it's just a matter of timing (when you remove the PhysicsVelocity)? I think this was never the case - 2 static bodies (bodies with no velocity are treated as static) never report a pair, simply because they are in the same tree that never gets a self overlap.

    Now if there is something that happens that keeps them kinematic/dynamic (like a wrong timing of removal of physics velocity or something like that), they would get a pair.
     
  18. WildMaN

    WildMaN

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    I've upgraded from 0.4.1 and it definitely behave differently now. Can't say 100% it's precisely due to upgrade as I had to tweak some stuff here and there to accommodate for fixedUpdate, but the core issue is definitely about body pairs not being generated.

    I'm a bit confused of terminology; is mere absence of PV makes a body static? What about kinematic bodies? My setup is "Motion type: Dynamic" in PhysicsBody authoring and then I add/remove PhysicsVelocity, PhysicsCollider and/or PhysicsExclude based on my heuristics.

    I'm doing some optimizations around colliding bodies to make it 60fps on mobile, part of that is processed in BodyPairs job. Before 0.5 update it correctly processed colliding bodies stripped of PV in the same frame by other systems.
     
  19. petarmHavok

    petarmHavok

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    Missing PV definitely makes the body static. Kinematic bodies do have PV, but their physics mass is set to infinite to avoid them being affected by impulses. But they will overlap correctly. PhysicsExclude completely removes stuff from simulation. My guess (I don't have a lot of info, so sorry it's basically just a guess) - timing/ordering issue. And yes, fixed update upgrade probably caused it, we had to tweak a bunch of samples demos a lot to accommodate for this properly.
     
  20. WildMaN

    WildMaN

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    I see, thanks for the clarification! Any advice then how to make an event similar to OnCollisionStay for objects which might loose PV anytime?
     
  21. petarmHavok

    petarmHavok

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    Why don't you keep them kinematic instead? Just set inverse mass and inverse inertia to 0. They keep all the events but nothing will move them. Just make sure velocity (both linear and angular) is 0.
     
  22. HeliosJack

    HeliosJack

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    Something in 0.5.0 is preventing the export of motion data from PhysicsBodies that do not have a collider. It seems like the entitygroup hasn't changed so I'm still investigating the problem.

    The motion data is definitely calculated but the export system never runs:
     

    Attached Files:

  23. HeliosJack

    HeliosJack

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    Update:
    Its evidently only affecting the initial query for whether the system should run. if theres at least one entity with a collider, the system will run and all valid dynamic entities will be exported.

    Dont know what happened that caused the PhysicsCollider to gatekeep the ExportPhysicsWorld system. probably an easy fix @CookieSalad . Ill let you know if I find it
     
  24. WildMaN

    WildMaN

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    This was my initial setup back then with Physics 0.2 and it was super buggy. Reworked my code now with 0.5 to use zero InverseMass and unfortunately it's still weird and buggy. The one issue I cant work around of I've reported as Case 1282300. Kinematic body is affected by gravity.
     
  25. petarmHavok

    petarmHavok

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    Kinematic bodies by default get a gravity factor of 0, meaning gravity isn't affecting them. Now if you are making them manually, please make sure to add PhysicsGravityFactor component data with a value of 0 to the bodies.
     
  26. WildMaN

    WildMaN

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    Ok, that's counter intuitive at least, but please check the bug report. The behavior is inconsistent between Unity and Havok physics and is depending on PhysicsShape component as well.
     
    goncalo-vasconcelos likes this.
  27. Baggers_

    Baggers_

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    Just upgraded from the the april preview release and the improvement in stability is awesome. Phenomenal work!
    (Also tried the Havok backend for the first time and the conversion was seamless. Super impressive stuff folks)
     
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  28. Sab_Rango

    Sab_Rango

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    Yeah, the independent frame rate of gpu render and cpu physics is the best! I hope another calculations in dots can be configurable like this one!
     
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  29. WildMaN

    WildMaN

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    Ok, have tried the new smoothing along with the fixed update and it's really helpful! Even when physics loop drops below 10fps, the game feels waaay more responsive and smooth compared to 0.4 . And surprisingly the only thing broken by smoothing is direct Translation animation, which I had to rework to LocalToWorld.
     
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  30. petarmHavok

    petarmHavok

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    There will be minor improvements to this in the coming release, but I'm glad you like it even now!
     
  31. Wobbers

    Wobbers

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    After updating I noticed objects now fall out of my world or sink into objects. I have different subscenes for static stuff and dynamic bodies. With previous versions this was not an issue, but now it seems the order of subscene loading or maybe physics happening in parallel with subscene loading can cause issues.
     
  32. petarmHavok

    petarmHavok

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    Physics systems have moved to the fixed step group in this release, so any code relying on them or interfering with them needs to adjust to that. Minor sinking of bodies can also be due to the interpolation (motion smoothing). We would need more info to investigate this.
     
  33. rz_0lento

    rz_0lento

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    I did notice that if you try the samples on actual build (with the default launcher), fixed time steps only apply if you load the scene from the launcher menu, if you refresh the scene or swap the scene from the left and right UI arrows, it will run the physics uncapped again.

    Edit: Apparently it does have some catchup kinda situation where it does go to fixed timesteps eventually but in most examples the demonstration of the scene's physics has been done at that point.
     
    Last edited: Oct 21, 2020
  34. petarmHavok

    petarmHavok

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    We've fixed the issue with kinematic bodies having gravity applied, it will be available in the next release (soon). Still looking into the inconsistency between the two engines.
     
  35. petarmHavok

    petarmHavok

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    Seems like it's the integrity checks we just added. For the time being, you can comment out the CheckIntegrity() call in the ExportPhysicsWorld, should be enough to get you moving.

    We're already working on a proper fix.
     
  36. nyanpath

    nyanpath

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    Why isn't Unity.Physics showing up for me? Am I blind? Bilde_2020-10-31_155153.png

    [edit] I had to manually add the com.unity.physics URL...
     
    Last edited: Oct 31, 2020
  37. CookieSalad

    CookieSalad

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    Hey everyone!

    Last Friday a small patch release addressing a few issues dropped - Unity.Physics-0.5.1preview.2. Today, we've also released an updated set of Physics Samples.

    As usual, let us know if you encounter any problems with the releases!
     
    GliderGuy likes this.
  38. Onigiri

    Onigiri

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    Input stopped working for me in sample scenes after release 0.5 or so
     
  39. snacktime

    snacktime

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    Thanks for BuildPhysicsWorld.AddDependencyToComplete()!

    Final item on my pain point list is Mesh being internal. We use this similarly to how the debug tools do, to iterate over geometry in physics.
     
    petarmHavok likes this.
  40. lndcobra

    lndcobra

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    I had to remove `#if UNITY_INPUT_SYSTEM_EXISTS` (am a Unity noob and not sure yet where to set pre-processor directives)
     
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  41. Onigiri

    Onigiri

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    Thanks, it's working. You can set it in Project settings> Player> Scripting define symbols
     
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