What a proper way to scale SphereCollider?

Hello everyone!
I have a 3d model with

Code (CSharp):

1. PhysicsShape
2. {
3.     ShapeType = Sphere,
4.     Radius = 0.335,
5.     Center = 0.29,
6. }

and it works fine until I change scale of the collider

To change the scale I grabbed code from the
UnityPhysicsSamples project,
5b. Change Collider Size
and modified it:

Code (CSharp):

1.  
2. using Unity.Entities;
3. using Unity.Jobs;
4. using Unity.Physics;
5. using Unity.Physics.Systems;
6. using Unity.Transforms;
7. using UnityEngine;
8. using Math = System.Math;
9. using SphereCollider = Unity.Physics.SphereCollider;
10.  
11. [UpdateBefore(typeof(BuildPhysicsWorld))]
12. public class ChangeVolumeSystem : JobComponentSystem
13. {
14.     protected override JobHandle OnUpdate(JobHandle inputDependencies)
15.     {
16.         var deltaTime = Time.DeltaTime;
17.         JobHandle jobHandle = Entities.ForEach(
18.             (
19.                 ref PhysicsCollider collider,
20.                 ref Scale scale,
21.                 in FoodAcceptorComponent foodAcceptor
22.             ) =>
23.             {
24.                 ChangeVolume(
25.                     deltaTime,
26.                     ref collider,
27.                     ref scale,
28.                     in foodAcceptor);
29.             }).Schedule(inputDependencies);
30.  
31.         return jobHandle;
32.     }
33.  
34.     private static unsafe void ChangeVolume(
35.         float deltaTime,
36.         ref PhysicsCollider collider,
37.         ref Scale scale,
38.         in FoodAcceptorComponent foodAcceptor
39.     )
40.     {
41.         var actualVolume = Conversions.ConvertSizeToVolume(scale.Value, foodAcceptor.VolumeFactor);
42.         if (Math.Abs(1 - foodAcceptor.Volume / actualVolume) < 0.001)
43.             return;
44.  
45.         // make sure we are dealing with spheres
46.         if (collider.ColliderPtr->Type != ColliderType.Sphere)
47.             return;
48.  
49.         var targetSize = Conversions.ConvertVolumeToSize(foodAcceptor.Volume, foodAcceptor.VolumeFactor);
50.         var lerpStep = deltaTime * foodAcceptor.SizeGrowingSpeed;
51.         var linearChangeFactor = (double) Mathf.Lerp(scale.Value, targetSize.ToFloat(), lerpStep) / scale.Value;
52.  
53.         // tweak the physical representation of the sphere
54.         // grab the sphere pointer
55.         SphereCollider* scPtr = (SphereCollider*) collider.ColliderPtr;
56.         var newRadius = (float) (scPtr->Radius * linearChangeFactor);
57.         var newCenter = (scPtr->Center * (float) linearChangeFactor);
58.  
59.         // update the collider geometry
60.         var sphereGeometry = scPtr->Geometry;
61.         sphereGeometry.Radius = newRadius;
62.         sphereGeometry.Center = newCenter;
63.         scPtr->Geometry = sphereGeometry;
64.         scale = new Scale() {Value = (scale.Value * linearChangeFactor).ToFloat()};
65.     }
66. }
67.  

The problem is that the code doesn't affect MassProperties what I can see by the PhysicsDebugDisplay component. And then the model behavior becomes weird by the eccentricity, it can even walk through a wall.
How can I manage the scale?

 

The problem here is that rigid body is still using the original mass properties of the sphere - stored in
the PhysicsMass component. There is currently nothing to detect that you have changed the collider and update the PhysicsMass of all the rigid bodies using it.

But you should be able to workaround it by passing PhysicsMass into your function above and recomputing it based on your sphere's new MassProperties - use PhysicsMass.CreateDynamic() as a reference for the math needed.

 

@Rory_Havok Thank you very much. It works great!
That is the final result:

Code (CSharp):

1. using Unity.Entities;
2. using Unity.Jobs;
3. using Unity.Mathematics;
4. using Unity.Physics;
5. using Unity.Physics.Systems;
6. using Unity.Transforms;
7. using UnityEngine;
8. using Math = System.Math;
9. using SphereCollider = Unity.Physics.SphereCollider;
10.  
11. [UpdateBefore(typeof(BuildPhysicsWorld))]
12. public class ChangeVolumeSystem : JobComponentSystem
13. {
14.     protected override JobHandle OnUpdate(JobHandle inputDependencies)
15.     {
16.         var deltaTime = Time.DeltaTime;
17.         JobHandle jobHandle = Entities.ForEach(
18.             (
19.                 ref PhysicsCollider collider,
20.                 ref PhysicsMass physicsMass,
21.                 ref Scale scale,
22.                 in FoodAcceptorComponent foodAcceptor
23.             ) =>
24.             {
25.                 ChangeVolume(
26.                     deltaTime,
27.                     ref collider,
28.                     ref physicsMass,
29.                     ref scale,
30.                     in foodAcceptor);
31.             }).Schedule(inputDependencies);
32.  
33.         return jobHandle;
34.     }
35.  
36.     private static unsafe void ChangeVolume(
37.         float deltaTime,
38.         ref PhysicsCollider collider,
39.         ref PhysicsMass physicsMass,
40.         ref Scale scale,
41.         in FoodAcceptorComponent foodAcceptor
42.     )
43.     {
44.         var actualVolume = Conversions.ConvertSizeToVolume(scale.Value, foodAcceptor.VolumeFactor);
45.         if (Math.Abs(1 - foodAcceptor.Volume / actualVolume) < 0.01)
46.             return;
47.  
48.         // make sure we are dealing with spheres
49.         if (collider.ColliderPtr->Type != ColliderType.Sphere)
50.             return;
51.  
52.         var targetSize = Conversions.ConvertVolumeToSize(foodAcceptor.Volume, foodAcceptor.VolumeFactor);
53.         var lerpStep = deltaTime * foodAcceptor.SizeGrowingSpeed;
54.         var linearChangeFactor = (double) Mathf.Lerp(scale.Value, targetSize.ToFloat(), lerpStep) / scale.Value;
55.  
56.         // tweak the physical representation of the sphere
57.         // grab the sphere pointer
58.         SphereCollider* scPtr = (SphereCollider*) collider.ColliderPtr;
59.         var newRadius = (float) (scPtr->Radius * linearChangeFactor);
60.         var newCenter = (scPtr->Center * (float) linearChangeFactor);
61.  
62.         // update the collider geometry
63.         var sphereGeometry = scPtr->Geometry;
64.         sphereGeometry.Radius = newRadius;
65.         sphereGeometry.Center = newCenter;
66.         scPtr->Geometry = sphereGeometry;
67.         scale = new Scale() {Value = (scale.Value * linearChangeFactor).ToFloat()};
68.         physicsMass = PhysicsMass.CreateDynamic(scPtr->MassProperties, math.rcp(physicsMass.InverseMass));
69.     }
70. }
71.