Toggling collision events via script?

I didnt see that the docs or samples cover this, so I was wondering how(if so) would one toggle receiving collision events on/off from code?

 

Collision events can be toggled in 2 places based on the granularity you want. Either (a) they can be enabled in a specific contact jacobian or (b) enabled in the MaterialFlags in the Unity.Physics.Material of a ConvexCollider (referenced in a PhysicsCollider ComponentData)

(a) If you want an event for a specific collision between only specific bodies, I recommend you check out the ModidyContactJacobians sample. This code for that sample tweaks the Jacobian flags to get different results. For example, it may enable surface velocity by setting

manifold.JacobianFlags |= JacobianFlags.EnableSurfaceVelocity;

. You could similiarly call

manifold.JacobianFlags |= JacobianFlags.EnableCollisionEvent;

to raise an event for that specific contact manifold.

(b) A PhysicsCollider component data holds a Collider BlobAssetReference. If the Collider is cast to a ConvexCollider (checking its CollisionType == CollisionType.Convex), then you can get access to its Material and the MaterialFlags associated with that.
I knocked up some PhysicsColliderExtensions that might be handy, though tbh I haven't fully tested this sample code.

Spoiler

Code (CSharp):

1. using Unity.Physics;
2. using UnityEngine.Assertions;
3. using static Unity.Physics.Material;
4. using Material = Unity.Physics.Material;
5.  
6. public static class PhysicsColliderExtensions
7. {
8.     public static Material GetColliderMaterial(this ref PhysicsCollider collider)
9.     {
10.         Material material = Unity.Physics.Material.Default;
11.         Assert.IsTrue(collider.Value.Value.CollisionType == CollisionType.Convex);
12.         unsafe
13.         {
14.             var colliderPtr = (ConvexCollider*)collider.ColliderPtr;
15.             material = colliderPtr->Material;
16.         }
17.         return material;
18.     }
19.     public static void SetColliderMaterial(this ref PhysicsCollider collider, Material newMaterial)
20.     {
21.         Material material = Material.Default;
22.         Assert.IsTrue(collider.Value.Value.CollisionType == CollisionType.Convex);
23.         unsafe
24.         {
25.             var colliderPtr = (ConvexCollider*)collider.ColliderPtr;
26.             colliderPtr->Material = newMaterial;
27.         }
28.     }
29.     public static void SetColliderMaterialCollisionEvent(this ref PhysicsCollider collider, bool enableCollisionEvents)
30.     {
31.         var material = collider.GetColliderMaterial();
32.         if (enableCollisionEvents)
33.             material.Flags |= MaterialFlags.EnableCollisionEvents;
34.         else
35.             material.Flags &= ~MaterialFlags.EnableCollisionEvents;
36.  
37.         collider.SetColliderMaterial(material);
38.     }
39. }
40.  

 

Thanks stevee, option b was exactly what I was looking for, thanks for the explanation and especially the code!

 

Is it possible to access the Unity.Physics.Material of a Unity.Physics.PhysicsCollider without using

unsafe

code?

I noticed that you can access the CollisionFilter through

myPhysicsCollider.Value.Value.Filter

but I can't find anything similar for accessing the Material.

 

Unfortunately, that is not possible without unsafe code. The reason is that material can be different per instance (say in compound collider, same as filter), but it's not easy to "combine" materials of individual instances to easily have a hierarchy and have one at the top level (in the header), like we do for filters.

 

@petarmHavok: Thanks, hope it will be possible in a few years. Maybe at least some helper methods to read-only values.

 

So if we want to use the second method and I want the function to be generic for all collider types (BoxCollider, SphereCollider, ConvexCollider, CapsuleCollider, Triangle, Quad, Cylinder, Mesh, etc)... does that mean we have to write GetColliderMaterial() and SetColliderMaterial() functions with big fat switch statements that cover every single collider type?

 

It only boils down to 4 colliders - convex, compound, mesh, and terrain. For convex and terrain you can get the material instantly, for mesh and compound you need a leaf collider (which will be convex again). Sphere, box and others are all convex colliders and have the same layout, so the material can be grabbed in the similar way.

Even further, because all colliders support the same interfaces, you can do something like CharacterControllerUtilities.IsTrigger() method is doing:

collider.Value.GetLeaf(colliderKey, out ChildCollider leafCollider); // get the leaf collider for the collider, supported even by convex colliders

Unity.Physics.Material material = UnsafeUtility.AsRef<ConvexColliderHeader>(leafCollider.Collider).Material; // leaf collider is guaranteed to be convex

 

I took a look at CharacterControllerUtilities.IsTrigger(), but I'm failing to adapt it to the GetColliderMaterial() function.

Code (CSharp):

1. public static Unity.Physics.Material GetColliderMaterial2(in PhysicsCollider collider)
2. {
3.     unsafe {
4.         collider.Value.GetLeaf(colliderKey, out ChildCollider leafCollider);
5.         return Unity.Collections.LowLevel.Unsafe.UnsafeUtility.AsRef<ConvexColliderHeader>(leafCollider.Collider).Material;
6.     }
7. }

I'm running into two problems...

1) Where would we get colliderKey in this situation? CharacterControllerUtilities is getting it from a hit collision, but in this case we're not dealing with any collisions or raycasts.

2) GetLeaf isn't a member of collider.Value. I did find it in collider.Value.Value.GetLeaf(). I don't know how it works in IsTrigger() by using just Value instead of Value.Value. Maybe it's because of different package versions?

 

fyi... this is what i'm currently using...

Code (CSharp):

1.     public static Unity.Physics.Material GetColliderMaterial(in PhysicsCollider collider)
2.     {
3.         unsafe {
4.             switch (collider.ColliderPtr->Type) {
5.                 case ColliderType.Box: return ((Unity.Physics.BoxCollider*)collider.ColliderPtr)->Material;
6.                 case ColliderType.Sphere: return ((Unity.Physics.SphereCollider*)collider.ColliderPtr)->Material;
7.                 case ColliderType.Convex: return ((Unity.Physics.ConvexCollider*)collider.ColliderPtr)->Material;
8.                 case ColliderType.Capsule: return ((Unity.Physics.CapsuleCollider*)collider.ColliderPtr)->Material;
9.                 case ColliderType.Triangle: return ((Unity.Physics.PolygonCollider*)collider.ColliderPtr)->Material;
10.                 case ColliderType.Quad: return ((Unity.Physics.PolygonCollider*)collider.ColliderPtr)->Material;
11.                 case ColliderType.Cylinder: return ((Unity.Physics.CylinderCollider*)collider.ColliderPtr)->Material;
12.                 case ColliderType.Terrain: return ((Unity.Physics.TerrainCollider*)collider.ColliderPtr)->Material;
13.             }
14.             // NOTE - MESH AND COMPOUND DON'T HAVE A MATERIAL
15.         }
16.         return Unity.Physics.Material.Default;
17.     }

 

Yeah I get what you are saying, collider key is there to identify children of compounds/meshes. You can treat all of the convex shapes in your function (other than terrain) in the same manner using the UnsafeUtility.AsRef<ConvexColliderHeader>, for simplicity. But yeah, your function is the way to go.

Btw, character controller works on BlobAssetReference<Collider>, this is one level of indirection less than PhysicsCollider, thus the extra .Value in your code. It has nothing to do with package versions.