How can I correctly integrate multiple animated .scn models into one SceneKit scene?

When you see unexpected behavior when merging models from separate scene files, it’s typically because the node’s transforms (or pivots) and even animation data aren’t set up to work together out of the box. Here are a few things to check and try:

1. Verify Node Hierarchy and Transforms
   When you load a node from an enemy.scn file using:

   SWIFTCopied
   let enemyNode = enemyScene.rootNode.childNode(withName: "enemy", recursively: true)

   make sure that the “enemy” node isn’t just a component of a larger node hierarchy. In some cases your scene might include a container node that applies a transform (position, scale, or rotation) that’s vital for proper placement. If you add just the child node without that container, it might appear “broken” or misaligned. Consider adding the appropriate parent node if one exists, or adjust the enemy node’s transform manually.

2. Use a Wrapper Node
   If you need to combine the enemy node into your playerWalk scene, wrap it in an empty container node first so that you can:

   • Adjust the position, rotation, and scale to match the coordinate space of your main scene.
   • Apply a custom pivot if needed.

   For example:

   SWIFTCopied
   let enemyContainer = SCNNode()
   if let enemyNode = enemyScene.rootNode.childNode(withName: "enemy", recursively: true) {
       enemyContainer.addChildNode(enemyNode)
       // Adjust the container’s transform as needed
       enemyContainer.position = SCNVector3(0, 0, 0) // reposition accordingly
   }
   mainScene.rootNode.addChildNode(enemyContainer)

3. Check for Animation and Rigging Issues
   If the “enemy” node is animated, it might rely on a specific skeleton hierarchy or animation data that isn’t preserved when you only add one child. Verify that you have imported all related nodes and that the animation players are still connected. Sometimes it’s better to load the entire scene for an animated model rather than just a child node.

4. SCNReferenceNode Consideration
   If your project requires dynamically loading parts of a scene, consider using an SCNReferenceNode. This lets you reference external scene assets so that SceneKit correctly handles the transform and animation data from the imported file. You can create a reference node like so:

   SWIFTCopied
   let enemyReference = SCNReferenceNode(url: Bundle.main.url(forResource: "enemy", withExtension: "scn")!)
   enemyReference?.load()
   mainScene.rootNode.addChildNode(enemyReference!)

   Using SCNReferenceNode can sometimes solve integration issues because it encapsulates the entire scene content (including proper transforms and animation groups).

By checking the node hierarchy, adjusting transforms, ensuring all animation data is included, or using SCNReferenceNode, you can merge your models more reliably. This should resolve the “broken piece” appearance of the enemy when it’s added to the main scene.

Remember to debug by printing the enemy node’s transform and comparing it with what you expect in the main scene coordinate space.