# Physics **URL:** https://discussions.unity.com/c/physics/174.md [Latest](https://discussions.unity.com/latest.md) · [Categories](https://discussions.unity.com/categories.md) · [Tags](https://discussions.unity.com/tags.md) --- ## [About the Physics category](https://discussions.unity.com/t/about-the-physics-category/1720661)
**Author:** [@osmangormus](https://discussions.unity.com/u/osmangormus)\ **Replies:** 0\ **Last updated:** [May 21, 2026, 11:12am UTC](https://discussions.unity.com/t/about-the-physics-category/1720661 "2026-05-21T11:12:20Z")
Tweak rigidbodies, joints, and collision matrices for physics simulations. Discuss raycasts and collision detection; state your 2D or 3D engine. --- ## [Is there a guide of how to code the physics of a bouncing ball in 2D isometric space?](https://discussions.unity.com/t/is-there-a-guide-of-how-to-code-the-physics-of-a-bouncing-ball-in-2d-isometric-space/1741594)
**Author:** [@Perspont](https://discussions.unity.com/u/Perspont)\ **Replies:** 2\ **Last updated:** [November 12, 2026, 5:01am UTC](https://discussions.unity.com/t/is-there-a-guide-of-how-to-code-the-physics-of-a-bouncing-ball-in-2d-isometric-space/1741594 "2026-11-12T05:01:04Z")
I’m attempting to code a bouncing ball in 2D isometric space, and want to toss it back and forth. I’d love to know if there are any resources that cover this specifically. If in Unity, even better. --- ## [Disabling and enabling physics at runtime](https://discussions.unity.com/t/disabling-and-enabling-physics-at-runtime/1741646)
**Author:** [@Sinister-Design](https://discussions.unity.com/u/Sinister-Design)\ **Replies:** 3\ **Last updated:** [November 12, 2026, 4:55am UTC](https://discussions.unity.com/t/disabling-and-enabling-physics-at-runtime/1741646 "2026-11-12T04:55:46Z")
I’ve just updated my engine from Unity 2021 to Unity 6.6 and I’m trying to figure out how to change my old code disabling and enabling physics. Unity is telling me to stop using Physics.autoSimulation in favor of Physic… --- ## [DOTS Physics and determinism](https://discussions.unity.com/t/dots-physics-and-determinism/736199)
**Author:** [@PsychoHead](https://discussions.unity.com/u/PsychoHead)\ **Replies:** 15\ **Last updated:** [November 11, 2026, 1:10pm UTC](https://discussions.unity.com/t/dots-physics-and-determinism/736199 "2026-11-11T13:10:51Z")
Hello all, I’ve been looking into the new Unity Physics documentation and one thing stood out to me: Now I’ve researched cross platform/architecture physics determinism in the past and came to the conclusion, that it’… --- ## [Experimental contacts modification API](https://discussions.unity.com/t/experimental-contacts-modification-api/798637)
**Author:** [@yant](https://discussions.unity.com/u/yant)\ **Replies:** 263\ **Last updated:** [November 8, 2026, 11:13pm UTC](https://discussions.unity.com/t/experimental-contacts-modification-api/798637 "2026-11-08T23:13:37Z")
Hi, EDIT: A newer build here: #22 tl;dr - here is a custom build with the experimental contact modifications API exposed: https://beta.unity3d.com/download/7a80bceabf9d/public\_download.html. It is based on 2020.2.a8 an… --- ## [Subject: Physics backend plugin API (Unity 7,6.6): an external backend cannot end a trigger pair silently](https://discussions.unity.com/t/subject-physics-backend-plugin-api-unity-7-6-6-an-external-backend-cannot-end-a-trigger-pair-silently/1739356)
**Author:** [@Cloudwalker](https://discussions.unity.com/u/Cloudwalker)\ **Replies:** 2\ **Last updated:** [November 2, 2026, 7:17pm UTC](https://discussions.unity.com/t/subject-physics-backend-plugin-api-unity-7-6-6-an-external-backend-cannot-end-a-trigger-pair-silently/1739356 "2026-11-02T19:17:32Z")
We implement a custom physics backend through IUnityPhysicsBackendSystem. We measured Unity 7000.0.0a7 and 6000.6.5f1, with manual stepping (Physics.Simulate) in both threading modes: the messages are the same, tick for … --- ## [Trying to understand Physics.ContactModifyEvent](https://discussions.unity.com/t/trying-to-understand-physics-contactmodifyevent/1619821)
**Author:** [@joshrs926](https://discussions.unity.com/u/joshrs926)\ **Replies:** 15\ **Last updated:** [November 1, 2026, 4:18am UTC](https://discussions.unity.com/t/trying-to-understand-physics-contactmodifyevent/1619821 "2026-11-01T04:18:59Z")
I’m trying to understand the rules for what GetPoint() and GetNormal() represent in ModifiableContactPair. The normal appears to always aim (from GetPoint()) towards the collider that is not the “other” collider. Is thi… --- ## [Separate Physics and Rendering layers](https://discussions.unity.com/t/separate-physics-and-rendering-layers/683444)
**Author:** [@varfare](https://discussions.unity.com/u/varfare)\ **Replies:** 137\ **Last updated:** [October 30, 2026, 8:23am UTC](https://discussions.unity.com/t/separate-physics-and-rendering-layers/683444 "2026-10-30T08:23:42Z")
https://feedback.unity3d.com/suggestions/separate-physics-and-render-laye It is a longstanding Unity issue. Layers are used for both Physics and Rendering. This is probably fine for small games but when you start creati… --- ## [How expensive is Physics.SyncTransforms()](https://discussions.unity.com/t/how-expensive-is-physics-synctransforms/901264)
**Author:** [@Lekret](https://discussions.unity.com/u/Lekret)\ **Replies:** 18\ **Last updated:** [October 24, 2026, 12:07am UTC](https://discussions.unity.com/t/how-expensive-is-physics-synctransforms/901264 "2026-10-24T00:07:53Z")
We are using ECS (Entitas) in our logic and I found that when I move moving platforms and then move player the player jitters a lot when moved by platform or when standing on it, i.e. many different bugs. I found that i… --- ## [Unity 2D: How to Make a Thrown Grenade Stop Following the Player?](https://discussions.unity.com/t/unity-2d-how-to-make-a-thrown-grenade-stop-following-the-player/1739979)
**Author:** [@Dkop1306](https://discussions.unity.com/u/Dkop1306)\ **Replies:** 2\ **Last updated:** [October 22, 2026, 8:18am UTC](https://discussions.unity.com/t/unity-2d-how-to-make-a-thrown-grenade-stop-following-the-player/1739979 "2026-10-22T08:18:35Z")
Hi everyone! I need some help with a grenade mechanic in Unity 2D. I’m trying to create a grenade by following this YouTube tutorial: ChannelThe Game Guy: How to throw knife using touch in UNITY - 2D I created a grena… --- ## [Physics development status and next milestones - May 2025](https://discussions.unity.com/t/physics-development-status-and-next-milestones-may-2025/1637988)
**Author:** [@ashley\_unity](https://discussions.unity.com/u/ashley_unity)\ **Replies:** 41\ **Last updated:** [October 21, 2026, 9:11pm UTC](https://discussions.unity.com/t/physics-development-status-and-next-milestones-may-2025/1637988 "2026-10-21T21:11:16Z")
Hi, everyone! Following up on Unity’s roadmap presentation from GDC 2025 and our 2024 Physics Development Update, the Physics team at Unity is here to share a recap and more details about the latest news regarding the … --- ## [Articulation Bodies broken in latest Unity 6.3 (6000.3.24f1) LTS](https://discussions.unity.com/t/articulation-bodies-broken-in-latest-unity-6-3-6000-3-24f1-lts/1736293)
**Author:** [@Qleenie](https://discussions.unity.com/u/Qleenie)\ **Replies:** 8\ **Last updated:** [October 21, 2026, 1:53pm UTC](https://discussions.unity.com/t/articulation-bodies-broken-in-latest-unity-6-3-6000-3-24f1-lts/1736293 "2026-10-21T13:53:35Z")
Hi, just upgraded from 6000.3.18f1 to 6000.3.24f1. Next to other new issues, Articulation Bodies are broken; I get a message “The maximum limit of ArticulationBody hierarchy size is reached: hierarchy of articulations c… --- ## [How to optimize the 3 simulation stages of physics](https://discussions.unity.com/t/how-to-optimize-the-3-simulation-stages-of-physics/1738771)
**Author:** [@mubarakalmehairbi-codya](https://discussions.unity.com/u/mubarakalmehairbi-codya)\ **Replies:** 5\ **Last updated:** [October 13, 2026, 10:24pm UTC](https://discussions.unity.com/t/how-to-optimize-the-3-simulation-stages-of-physics/1738771 "2026-10-13T22:24:58Z")
I connected the CPU profiler to my dev build and found these 3 stages of physics: They cost much so I wanted to optimize them. I could not find them in Profiler Markers. I found some info in SimulationStage but no gu… --- ## [IUnityPhysicsBackendSystem: a registered backend can never be selected, because native plugins load after BackendSystem::Select (6000.3 and 6000.6)](https://discussions.unity.com/t/iunityphysicsbackendsystem-a-registered-backend-can-never-be-selected-because-native-plugins-load-after-backendsystem-select-6000-3-and-6000-6/1738344)
**Author:** [@OfficialDeVel](https://discussions.unity.com/u/OfficialDeVel)\ **Replies:** 1\ **Last updated:** [October 7, 2026, 7:23pm UTC](https://discussions.unity.com/t/iunityphysicsbackendsystem-a-registered-backend-can-never-be-selected-because-native-plugins-load-after-backendsystem-select-6000-3-and-6000-6/1738344 "2026-10-07T19:23:30Z")
I make a Box3D-based physics package for Unity Anvil Physics - Box3D for Unity and I’m looking at IUnityPhysicsBackendSystem in Unity 6.3. I’d like Box3D to show up as a GameObject SDK option next to PhysX. I wrote a s… --- ## [PhysX 4.1.2 Triangle Mesh CCD Can Discard a Valid Later Collision](https://discussions.unity.com/t/physx-4-1-2-triangle-mesh-ccd-can-discard-a-valid-later-collision/1736002)
**Author:** [@snaphat](https://discussions.unity.com/u/snaphat)\ **Replies:** 3\ **Last updated:** [October 7, 2026, 1:51am UTC](https://discussions.unity.com/t/physx-4-1-2-triangle-mesh-ccd-can-discard-a-valid-later-collision/1736002 "2026-10-07T01:51:53Z")
Unity’s built-in 3D physics uses PhysX 4.1.2, and I have confirmed a triangle mesh CCD bug in Unity 6000.5.3f1 that can cause a Rigidbody using CollisionDetectionMode.Continuous to tunnel through a MeshCollider. I repor… --- ## [My player keeps clipping through the grond after jumping](https://discussions.unity.com/t/my-player-keeps-clipping-through-the-grond-after-jumping/1737412)
**Author:** [@Chheby](https://discussions.unity.com/u/Chheby)\ **Replies:** 1\ **Last updated:** [October 4, 2026, 8:49pm UTC](https://discussions.unity.com/t/my-player-keeps-clipping-through-the-grond-after-jumping/1737412 "2026-10-04T20:49:20Z")
As the title states, after using AddForce on the player Rigidbody to simulate a jump, it clips through the ground collider ever so slightly. I’ve tried making the ground rigid body kinematic and allow full kinematic cont… --- ## [\`PhysicsComposer.CreateChainGeometry\` sometimes produces 2 shapes when 1 is expected](https://discussions.unity.com/t/physicscomposer-createchaingeometry-sometimes-produces-2-shapes-when-1-is-expected/1733045)
**Author:** [@jonaspuksta](https://discussions.unity.com/u/jonaspuksta)\ **Replies:** 2\ **Last updated:** [October 4, 2026, 7:08am UTC](https://discussions.unity.com/t/physicscomposer-createchaingeometry-sometimes-produces-2-shapes-when-1-is-expected/1733045 "2026-10-04T07:08:03Z")
I’m trying to turn a concave shape with a radius into an approximate polygon. The original concave shape without radius is red, the polygon approximation of the expanded shape is white and gray. The problem is that in th… --- ## [bouncing an object of a wall.](https://discussions.unity.com/t/bouncing-an-object-of-a-wall/907446)
**Author:** [@jermainetai0307](https://discussions.unity.com/u/jermainetai0307)\ **Replies:** 13\ **Last updated:** [September 20, 2026, 4:23pm UTC](https://discussions.unity.com/t/bouncing-an-object-of-a-wall/907446 "2026-09-20T16:23:30Z")
i want to make an object not really bounce but in fact more like go in the opposite direction with the same velocity. using System.Collections; using System.Collections.Generic; using UnityEngine; public class ballmove… --- ## [Making it so a rigidbody boat carries rigidbodies on top of it without them sliding off](https://discussions.unity.com/t/making-it-so-a-rigidbody-boat-carries-rigidbodies-on-top-of-it-without-them-sliding-off/1736903)
**Author:** [@tengowskit](https://discussions.unity.com/u/tengowskit)\ **Replies:** 3\ **Last updated:** [September 19, 2026, 1:52pm UTC](https://discussions.unity.com/t/making-it-so-a-rigidbody-boat-carries-rigidbodies-on-top-of-it-without-them-sliding-off/1736903 "2026-09-19T13:52:12Z")
Ive spent hours trying different solutions and browsing existing topics to no avail The boat- a rigidbody moved via forces- needs to be able to carry rigidbodies on top of it, including but not limited to the player. It… --- ## [PhysX 4.1.2 Triangle Mesh CCD Can Return the Shape Center as the Contact Point](https://discussions.unity.com/t/physx-4-1-2-triangle-mesh-ccd-can-return-the-shape-center-as-the-contact-point/1736579)
**Author:** [@snaphat](https://discussions.unity.com/u/snaphat)\ **Replies:** 0\ **Last updated:** [September 15, 2026, 12:40am UTC](https://discussions.unity.com/t/physx-4-1-2-triangle-mesh-ccd-can-return-the-shape-center-as-the-contact-point/1736579 "2026-09-15T00:40:16Z")
Unity’s built-in 3D physics uses PhysX 4.1.2, and I have confirmed a triangle mesh CCD bug in Unity 6000.5.3f1 where ContactModifyEventCCD can report the moving collider’s pre-simulation shape center as the contact point… --- ## [2D Weapon Sway](https://discussions.unity.com/t/2d-weapon-sway/1735871)
**Author:** [@flyzogirard](https://discussions.unity.com/u/flyzogirard)\ **Replies:** 2\ **Last updated:** [September 12, 2026, 7:45pm UTC](https://discussions.unity.com/t/2d-weapon-sway/1735871 "2026-09-12T19:45:35Z")
So I am trying to make a game where there is an axe that follows the mouse. The mouse holds the handle of the axe, so the head of the axe should have a sway. I now have a bug where if the axe goes for a long time in one … --- ## [Character Controller and mesh collider interaction BUG](https://discussions.unity.com/t/character-controller-and-mesh-collider-interaction-bug/1736188)
**Author:** [@hamzakhan201021](https://discussions.unity.com/u/hamzakhan201021)\ **Replies:** 2\ **Last updated:** [September 9, 2026, 8:23pm UTC](https://discussions.unity.com/t/character-controller-and-mesh-collider-interaction-bug/1736188 "2026-09-09T20:23:25Z")
Hi, we are having an awkward issue, in the starter assets you get this structure model which is setup with a MeshCollider, we are using collision flags in the character controller to ensure our sphere check isn’t false w… --- ## [PhysX 4.1.2 Contact Modification Uses the Wrong Normal for Additional Contact Patches](https://discussions.unity.com/t/physx-4-1-2-contact-modification-uses-the-wrong-normal-for-additional-contact-patches/1735986)
**Author:** [@snaphat](https://discussions.unity.com/u/snaphat)\ **Replies:** 0\ **Last updated:** [September 7, 2026, 5:31pm UTC](https://discussions.unity.com/t/physx-4-1-2-contact-modification-uses-the-wrong-normal-for-additional-contact-patches/1735986 "2026-09-07T17:31:12Z")
Unity’s built-in 3D physics uses PhysX 4.1.2, and as far as I can tell there is a bug in the upstream PhysX 4.1.2 contact modification path that can give contact patches the wrong normal. The relevant code is in PxcNpCo… --- ## [Slopes angles Raycast cast](https://discussions.unity.com/t/slopes-angles-raycast-cast/1735913)
**Author:** [@theizenyt](https://discussions.unity.com/u/theizenyt)\ **Replies:** 1\ **Last updated:** [September 7, 2026, 1:00pm UTC](https://discussions.unity.com/t/slopes-angles-raycast-cast/1735913 "2026-09-07T13:00:45Z")
using System.Collections.Generic; using UnityEngine; using VContainer; public class PlayerDetection : MonoBehaviour { \[Header("Links")\] private CapsuleCollider controller; \[Header("Settings, R… --- ## [Inverse Kinematics problem](https://discussions.unity.com/t/inverse-kinematics-problem/1735805)
**Author:** [@mostafamhazem](https://discussions.unity.com/u/mostafamhazem)\ **Replies:** 0\ **Last updated:** [September 5, 2026, 8:56pm UTC](https://discussions.unity.com/t/inverse-kinematics-problem/1735805 "2026-09-05T20:56:52Z")
i was trying to make a 2d stickman that moves with physics my main problem is with leg placement in the idle state i tried to use inverse kinematics my question is basically is this a correct way todo it it feels to… --- ## [Unity x Fortnite: How Unity Runs Inside Unreal Engine](https://discussions.unity.com/t/unity-x-fortnite-how-unity-runs-inside-unreal-engine/1731630)
**Author:** [@mfuad](https://discussions.unity.com/u/mfuad)\ **Replies:** 44\ **Last updated:** [September 3, 2026, 8:58am UTC](https://discussions.unity.com/t/unity-x-fortnite-how-unity-runs-inside-unreal-engine/1731630 "2026-09-03T08:58:39Z")
At Unite Seoul, we revealed the first concrete milestone in our partnership with Epic Games: Unity running natively inside Unreal Engine. Watch the Unite Seoul reveal segment → We want to explain the technical details … --- ## [Physics Core 2D - unexpected bounce](https://discussions.unity.com/t/physics-core-2d-unexpected-bounce/1734698)
**Author:** [@DKaras](https://discussions.unity.com/u/DKaras)\ **Replies:** 10\ **Last updated:** [September 1, 2026, 1:08pm UTC](https://discussions.unity.com/t/physics-core-2d-unexpected-bounce/1734698 "2026-09-01T13:08:26Z")
I have two scripts corresponding to a moving object (dynamic) and a static obstacle. Moving object has a linear velocity set upon its creation and is moving towards the obstacle. In PhysicsCoreSettings2D I set bouncine… --- ## [Issue with "Bouncy" like projectiles](https://discussions.unity.com/t/issue-with-bouncy-like-projectiles/1735189)
**Author:** [@zendos13367](https://discussions.unity.com/u/zendos13367)\ **Replies:** 4\ **Last updated:** [August 30, 2026, 6:39pm UTC](https://discussions.unity.com/t/issue-with-bouncy-like-projectiles/1735189 "2026-08-30T18:39:47Z")
Greetings everyone! I used tutorial for projectiles, added some tweak myself and it works weird. Intended behavior: Bounce out of collision marked with GROUND layer. Current behavior: At specific angles, projec… --- ## [Physics.Raycast stopped working (now always returns false)](https://discussions.unity.com/t/physics-raycast-stopped-working-now-always-returns-false/1594431)
**Author:** [@StevenRhinox](https://discussions.unity.com/u/StevenRhinox)\ **Replies:** 14\ **Last updated:** [August 27, 2026, 4:38pm UTC](https://discussions.unity.com/t/physics-raycast-stopped-working-now-always-returns-false/1594431 "2026-08-27T16:38:09Z")
I’m trying to select bolts in a machine by clicking on them. The bolts have a sphere-collider on them, and I cast a ray from the camera, but Physics.Raycast() always returns false. I checked the value of mousePos, but … --- ## [Low-level 2D Physics in Unity 6.3](https://discussions.unity.com/t/low-level-2d-physics-in-unity-6-3/1683247)
**Author:** [@rustum](https://discussions.unity.com/u/rustum)\ **Replies:** 104\ **Last updated:** [August 27, 2026, 3:08pm UTC](https://discussions.unity.com/t/low-level-2d-physics-in-unity-6-3/1683247 "2026-08-27T15:08:57Z")
What is it? Low-level 2D Physics based upon the latest Box2D v3 is now available in Unity 6.3 beta A new API that empowers developers with direct access to a powerful new physics system, providing the ability to… [Next page](https://discussions.unity.com/c/physics/174.md?page=1)