SceneKit中Swift相机沿Z轴每帧自动移动失效问题求助

Hey there! It sounds like your current code is only triggering the camera movement a few times instead of every frame. The most common issue here is that you're not hooking into SceneKit's per-frame update cycle properly. Let's fix that with a reliable implementation:

Step-by-Step Correct Code #

First, make sure your view controller conforms to SCNSceneRendererDelegate—this gives you access to the per-frame update callback. Here's a complete example:

import UIKit
import SceneKit

class ViewController: UIViewController, SCNSceneRendererDelegate {
    private var scnView: SCNView!
    private var cameraNode: SCNNode!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // Set up the SceneKit view
        scnView = SCNView(frame: view.bounds)
        scnView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        scnView.backgroundColor = .black
        view.addSubview(scnView)
        
        // Create an empty scene
        let scene = SCNScene()
        scnView.scene = scene
        
        // Create and configure the camera node
        cameraNode = SCNNode()
        cameraNode.camera = SCNCamera()
        cameraNode.position = SCNVector3(x: 0, y: 0, z: 10) // Starting position
        scene.rootNode.addChildNode(cameraNode)
        
        // Enable per-frame updates by setting the delegate
        scnView.delegate = self
        
        // Start the scene's animation loop
        scnView.play(nil)
    }
    
    // This method is called EVERY frame by SceneKit
    func renderer(_ renderer: SCNSceneRenderer, updateAtTime time: TimeInterval) {
        // Adjust the Z position here—negative values move the camera forward, positive moves back
        // Tweak the 0.1 value to change movement speed
        cameraNode.position.z -= 0.1
        
        // Optional: Add a boundary to stop movement if needed
        // if cameraNode.position.z > -50 {
        //     cameraNode.position.z -= 0.1
        // }
    }
}

Key Fixes & Explanations #

• Per-Frame Callback: The renderer(_:updateAtTime:) method is executed every single frame while the scene is running. This ensures your camera moves continuously, not just a few times.
• Delegate Setup: You must set scnView.delegate = self—without this, SceneKit won't call the update method.
• Animation Loop: Calling scnView.play(nil) starts SceneKit's internal animation loop, which drives the per-frame updates.

Why Your Original Code Stopped After 3 Frames #

Chances are you were using a one-time SCNAction with a limited repeat count, or you were updating the camera position only in a method that runs a few times (like viewDidLoad). By moving the position logic into the per-frame delegate method, you guarantee it runs every frame.

内容的提问来源于stack exchange，提问作者Johan Kornet