使用一些线性代数
func findNextPoint(p0: SCNVector3, direction: SCNVector3) -> SCNVector3{
var x = Float()
var y = Float()
var z = Float()
let t = 100 as Float
x = p0.x + t * direction.x
y = p0.y + t * direction.y
z = p0.z + t * direction.z
let result = SCNVector3Make(x, y, z)
return result
}
这里使用P0为出发点,那么,找到你想要在一个给定方向的下一个点。 t是矢量的长度,或者你想从p0行进的距离。
要找到相机指向的方向,您必须旋转并乘以旋转矩阵。
func calculateCameraDirection(cameraNode: SCNNode) -> GLKVector3 {
let x = -cameraNode.rotation.x
let y = -cameraNode.rotation.y
let z = -cameraNode.rotation.z
let w = cameraNode.rotation.w
let cameraRotationMatrix = GLKMatrix3Make(cos(w) + pow(x, 2) * (1 - cos(w)),
x * y * (1 - cos(w)) - z * sin(w),
x * z * (1 - cos(w)) + y*sin(w),
y*x*(1-cos(w)) + z*sin(w),
cos(w) + pow(y, 2) * (1 - cos(w)),
y*z*(1-cos(w)) - x*sin(w),
z*x*(1 - cos(w)) - y*sin(w),
z*y*(1 - cos(w)) + x*sin(w),
cos(w) + pow(z, 2) * (1 - cos(w)))
let cameraDirection = GLKMatrix3MultiplyVector3(cameraRotationMatrix, GLKVector3Make(0.0, 0.0, -1.0))
return cameraDirection
}
然后你只需要使用两个坐标来执行hitTest。在这种情况下,我使用了rayTestWithSegmentFromPoint:ToPoint,但您可以使用其他类型的测试,例如hitTestWithSegmentFromPoint:toPoint:。
func raycastTest(cameraDirection: GLKVector3) -> SCNVector3{
let nextPoint = findNextPoint(cameraNode.position, direction: SCNVector3Make(cameraDirection.x, cameraDirection.y, cameraDirection.z))
let hitTest = sceneView.scene!.physicsWorld.rayTestWithSegmentFromPoint(cameraNode.position, toPoint: nextPoint, options: nil)
if hitTest.count > 0 {
return (hitTest.first?.worldCoordinates)!
}else{
return nextPoint
}
}
非常非常感谢@KeyChainDude,我发现另一种方法由具有farNode作为相机的子节点,因此所有的旋转将它影响到,然后将它的坐标。但我会切换到这一个。 –