如何提高 RealityKit 物理模拟精度？

Question

我一直在尝试基于 RealityKit 构建台球游戏，但是物理模拟不够准确。当参数太小时，RealityKit 似乎会产生粗略的计算。

下面的代码展示了我到目前为止所做的事情。有没有办法配置 RealityKit 并提高物理精度？

import RealityKit
import ARKit

let ballMaterial = PhysicsMaterialResource.generate(friction: 0.055, restitution: 0.95)

game.allBalls.forEach { entity in
    guard let physicsEntity = entity as? HasPhysics else { return }
    
    physicsEntity.physicsBody?.massProperties.mass = 0.17
    physicsEntity.physicsBody?.material = ballMaterial
}

let wallMaterial = PhysicsMaterialResource.generate(friction: 0.005, restitution: 0.5)

game.wallEntities.forEach { entity in
    guard let physicsEntity = entity as? HasPhysics else { return }
    
    physicsEntity.physicsBody?.material = wallMaterial
}

let tableSurfaceMatrial = PhysicsMaterialResource.generate(staticFriction: 0.001, dynamicFriction: 0.2, restitution: 0.25)

game.tableSurfaceEntities.forEach { entity in
    guard let physicsEntity = entity as? HasPhysics else { return }
    
    physicsEntity.physicsBody?.material = tableSurfaceMatrial
}

添加一个力来移动白球：

// ballWhite as? Entity & HasPhysics
game.ballWhite.physicsBody?.mode = .dynamic
game.ballWhite.addForce(rayForce, relativeTo: nil)

ModelEntity: render physics entity

HasPhysics: physics protocol

Falling ball

Answer 1

如果您将restitution 参数设置为大于1 的值，RealityKit 物理引擎会开始生成更逼真的弹跳模拟，但在动态效果衰减时仍然不够逼真——Apple 工程师必须更加努力地实现鲁棒性RealityKit 3.0 中的物理模拟。

我使用了一个简单的 Reality Composer 场景，其中包含一个半径为 0.1 m 的球。

import AppKit
import RealityKit

class GameViewController: NSViewController {
    
    @IBOutlet var arView: ARView!
    
    override func awakeFromNib() {

        arView.environment.background = .color(.black)
        
        let ballScene = try! Experience.loadBall()

        let ball = ballScene.sphere!.children[0] as! ModelEntity
        
        ball.components[CollisionComponent.self] = 
                        CollisionComponent(shapes: [.generateSphere(radius: 0.1)], 
                                             mode: .default, 
                                           filter: .sensor)

        ball.components[PhysicsBodyComponent.self] = 
                        PhysicsBodyComponent(shapes: [.generateSphere(radius: 0.1)], 
                                               mass: 0.05, 
                                           material: .generate(friction: 0.9, 
                                                            restitution: 1.35))
        
        arView.scene.anchors.append(ballScene)
    }
}