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swiftaugmented-realityarkitrealitykit

Within RealityKit, how can I make the world without friction?

I want to make the physics world without friction and damping.

I tried to make the scene's gravity to (0,0,0), and make a square and ball, give force when tapping. I want to make the ball move eternally, but it just stop in some time.

How can I make the entities friction to zero?

enter image description here

Solution

  • Apply a new Physics Material to your model entity.

    For this use generate(friction:restitution:) type method:

    static func generate(friction: Float = 0, 
                  restitution: Float = 0) -> PhysicsMaterialResource

    where

    /*   the coefficient of friction is in the range [0, infinity]   */

/*   and the coefficient of restitution is in the range [0, 1]   */

    Here's a code:

    arView.environment.background = .color(.darkGray)

let mesh = MeshResource.generateSphere(radius: 0.5)
let material = SimpleMaterial()
let model = ModelEntity(mesh: mesh,
                   materials: [material]) as (ModelEntity & HasPhysics)
    
let physicsResource: PhysicsMaterialResource = .generate(friction: 0, 
                                                      restitution: 0)
    
model.components[PhysicsBodyComponent] = PhysicsBodyComponent(
                                        shapes: [.generateSphere(radius: 0.51)],
                                          mass: 20,         // in kilograms
                                      material: physicsResource, 
                                          mode: .dynamic)

model.generateCollisionShapes(recursive: true)

let anchor = AnchorEntity()
anchor.addChild(model)
arView.scene.anchors.append(anchor)

    P.S. Due to some imperfectness of physics engine in RealityKit, I suppose there's no possibility to create an eternal bouncing. Seemingly next RealityKit's update will fix physics engine imperfectness.