Bug Problems with rigidbody collisions in the Webgl build

Hello,

I have issues with the rigibodies that use box colliders in the WebGL build. Sometimes the collisions are simply skipped and they penetrate through each other. The issue happens only in the build, but never happens in Unity Editor.

Here is the video, and below explanation what's happening:

The rigidbody 1 (the red box) is being moved normally, using AddForce in FixedUpdate. Force type can be Velocity or Force, reproduced with both. The rigidbody 2 (the blue box) is staying. When rigidbody 1 collides with rigidbody 2, it passes sometimes through, without colliding.

When this happens for the first time, it starts passing through more often (sometimes all the time) when trying again. It happens under framerate of 60 fps, so the performance is not the issue.

The collision detection is set to Continious Speculative. It happens even when the sleeping of the rigidbody 2 is permanently disabled by setting sleepTreshold to 0. It also happens when rigidbody 1 is moving very slow, so it is clearly not a speed issue.

I reproduce this consistently with Unity 2020.3.7f1 and earlier 2020.3 versions.

Have anybody faced this issue, and does there exist any workaround? So far I tried to play with all the different physics settings, but nothing helps.

 

Looks like a bug to me, and you have a pretty clear repro scene. I'd file a bug report with it.

 

I have already reported a bug with the demo project atrached. But maybe somebody faced it and knows a workaround before they fix it.

 

I have found how to work around the issue for now by adding a script to the moving rigidbodies, that uses raycast to detect collisions. I have taken inspiration from here and slightly modified it so it actually works for this case. It does not always look the best but is acceptable workaround. If anybody has this issue, here is the code:

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3. using System.Linq;
4.  
5. public class DontGoThroughThings : MonoBehaviour
6. {
7.     public LayerMask layerMask = -1;
8.     public float skinWidth = 0.1f;
9.  
10.     public float searchCollisionVerticalOffset = 0.5f;
11.     private float minimumExtent;
12.     private float partialExtent;
13.     private Vector3 previousPosition;
14.     private Rigidbody myRigidbody;
15.     private Collider myCollider;
16.    
17.     void Start()
18.     {
19.         myRigidbody = GetComponent<Rigidbody>();
20.         myCollider = GetComponent<Collider>();
21.         previousPosition = myRigidbody.position;
22.         minimumExtent = Mathf.Min(Mathf.Min(myCollider.bounds.extents.x, myCollider.bounds.extents.y), myCollider.bounds.extents.z);
23.            partialExtent = minimumExtent * (1.0f - skinWidth);
24.     }
25.  
26.     void FixedUpdate()
27.     {
28.         if (myRigidbody.velocity.sqrMagnitude < 0.0001f) {
29.             return;
30.         }
31.  
32.         Vector3 movementThisStep = myRigidbody.position - previousPosition;
33.         float movementSqrMagnitude = movementThisStep.sqrMagnitude;
34.      
35.         if (movementSqrMagnitude > 0)
36.         {
37.             float movementMagnitude = Mathf.Sqrt(movementSqrMagnitude);
38.             var isObstacle = FindObstacle(previousPosition + Vector3.up * searchCollisionVerticalOffset, movementThisStep, movementMagnitude, layerMask.value, out var hitInfo);
39.  
40.             if (isObstacle)
41.             {
42.                 if (hitInfo.collider.isTrigger) {
43.                     hitInfo.collider.SendMessage("OnTriggerEnter", myCollider);
44.                 }
45.                 else {
46.                     myRigidbody.position = hitInfo.point - Vector3.up * searchCollisionVerticalOffset - (movementThisStep / movementMagnitude) * partialExtent;
47.                 }
48.             }
49.         }
50.         previousPosition = myRigidbody.position;
51.     }
52.  
53.     private bool FindObstacle(Vector3 position, Vector3 step, float distance, int layers, out RaycastHit hitInfo) {
54.         var hits = Physics.RaycastAll(position, step, distance, layers);
55.         foreach (var hit in hits) {
56.             if (hit.collider != myCollider) {
57.                 hitInfo = hit;
58.                 return true;
59.             }
60.         }
61.         hitInfo = default(RaycastHit);
62.         return false;
63.     }
64. }
65.  

 

I don't have the public link to my bug case. I have reported the bug through Unity Editor, and all I got is a private link of the inquiry, that it says I'm not supposed to share. The inquiry id number, if this helps you to find it in the system is: 1334972

 

What is the status of this bug? I can't find it in the public issue tracker.

 

@MelvMay, @ndruha, Same problem. In my project, some objects fall into the ground.

I've done a lot of testing and I can say that this is clearly a Unity bug and only appears on webGL.
I solved this with Physics.Raycast() but would like to do without it, but I don't think the Unity team will fix it.

Unity 2019.4.37f

 

I looked at this link and I think this issue is not well researched.

As far as I know, the version of the physics engine has not changed in version 2019.4.X, but this problem appeared.
Although in the previous version of Unity 2019.2.X there was no such problem.