I'm trying to detect when two entities collide. The following code shows a very basic set-up. How do I get the upperSphere to move? If I set its physicsBody.mode to .dynamic it moves with gravity (and the collision is reported), but when in kinematic mode it doesn't respond to the impulse:
struct CollisionView: View {
@State var subscriptions: [EventSubscription] = []
var body: some View {
RealityView { content in
let upperSphere = ModelEntity(mesh: .generateSphere(radius: 0.04))
let lowerSphere = ModelEntity(mesh: .generateSphere(radius: 0.04))
upperSphere.position = [0, 2, -2]
upperSphere.physicsBody = .init()
upperSphere.physicsBody?.mode = .kinematic
upperSphere.physicsMotion = PhysicsMotionComponent()
upperSphere.generateCollisionShapes(recursive: false)
lowerSphere.position = [0, 1, -2]
lowerSphere.physicsBody = .init()
lowerSphere.physicsBody?.mode = .static
lowerSphere.generateCollisionShapes(recursive: false)
let sub = content.subscribe(to: CollisionEvents.Began.self, on: nil) { _ in print("Collision!") }
subscriptions.append(sub)
content.add(upperSphere)
content.add(lowerSphere)
Task {
try? await Task.sleep(for: .seconds(2))
print("Impulse applied")
upperSphere.applyLinearImpulse([0, -1, 0], relativeTo: nil)
}
}
}
}
Hello @peggers123,
The PhysicsMotionComponent documentation explains the motion expectations for a kinematic physics body.
If you truly want your "upperSphere" to be a kinematic body, then you will need to set its velocity appropriately to make it move after the collision.
I have a hunch that you might want "upperSphere" to be a dynamic body, but one that is not affected by gravity: https://developer.apple.com/documentation/realitykit/physicsbodycomponent/isaffectedbygravity?changes=_6
