ARKit - Ball没有穿过“SCNTorus”洞

Question

我在ARKit上遇到了一个问题，我需要帮助。我正在制作一个小演示，我在场景中放置一个简单的SCNTorus几何体，我试图将一个小球（SCNSphere）扔进圆环洞。问题是球在中间弹跳而不是通过。环面的代码是：

let ring = SCNTorus(ringRadius: 0.4, pipeRadius: 0.1)
ring.ringSegmentCount = 100

let ringMaterial = SCNMaterial()
ringMaterial.diffuse.contents = UIImage(named: "art.scnassets/Ball/BeachBallColor.jpg")

ring.materials = [ringMaterial]

let ringNode = SCNNode()
ringNode.position = SCNVector3(x: location.worldTransform.columns.3.x,
                               y: location.worldTransform.columns.3.y + 0.8,
                               z: location.worldTransform.columns.3.z)

ringNode.geometry = ring

let body = SCNPhysicsBody(type: SCNPhysicsBodyType.kinematic,
                               shape: nil)
body.categoryBitMask = CollisionTypes.wall.rawValue
body.collisionBitMask = CollisionTypes.beachball.rawValue
// body.contactTestBitMask = CollisionTypes.beachball.rawValue
body.isAffectedByGravity = false
body.mass = 0.5

ringNode.physicsBody = body

sceneView.scene.rootNode.addChildNode(ringNode)

对于球：

let node = SCNNode(geometry: sphere!)
node.renderingOrder = 10

let body = SCNPhysicsBody(type: SCNPhysicsBodyType.dynamic,shape: nil)
body.categoryBitMask = CollisionTypes.beachball.rawValue
body.collisionBitMask = CollisionTypes.solid.rawValue|CollisionTypes.wall.rawValue|CollisionTypes.beachball.rawValue
// body.contactTestBitMask = CollisionTypes.fireball.rawValue|CollisionTypes.wall.rawValue
body.isAffectedByGravity = true
body.mass = 0.5
body.restitution = 0.75
body.damping = 0.1
body.friction = 0.8

node.physicsBody = body

Answer 1

用于创建物理实体的代码（体型kinametic和shape nil）导致几何体的简化“凸包”表示。简单地说，您看到的几何体是圆环面，但用于碰撞检测的几何体不是。

这行（obj c）代码实际上来自Apple示例代码项目之一：

_torus.physicsBody = [SCNPhysicsBody bodyWithType:SCNPhysicsBodyTypeStatic shape:[SCNPhysicsShape shapeWithGeometry:_torus.geometry options: @{SCNPhysicsShapeTypeKey : SCNPhysicsShapeTypeConcavePolyhedron} ] ];

换句话说，您需要使用SCNPhysicsShapeTypeConcavePolyhedron键值（仅适用于静态实体）创建基于几何体本身的静态类型实体和形状，以最终更准确地表示环面几何体作为物理实体。

有关详细信息，请参阅：https://developer.apple.com/documentation/scenekit/scnphysicsshape

Answer 2

谢谢！这行得通！有代码：

    let ring = SCNTorus(ringRadius: 0.4, pipeRadius: 0.1)
    ringNode.geometry = ring

    let shapeOptions = [ SCNPhysicsShape.Option.type : SCNPhysicsShape.ShapeType.concavePolyhedron]
    let physicShape = SCNPhysicsShape(geometry: ring, options: shapeOptions)

    let body = SCNPhysicsBody(type: SCNPhysicsBodyType.kinematic,
                              shape: physicShape)
    body.categoryBitMask = CollisionTypes.wall.rawValue
    body.collisionBitMask = CollisionTypes.beachball.rawValue
    body.isAffectedByGravity = false
    body.mass = 0.5
    ringNode.physicsBody = body