How to add 3D models to a scene so that they have certain XYZ position?

Question

I once wrote a function in which I added geometrical cones to the scene. It looked like this:

func addZombies(i:Int, x: Float, y: Float, z: Float)
{
    let node = SCNNode()
    node.geometry = SCNCone(topRadius: 0.0, bottomRadius: 1, height: 2)
    node.position = SCNVector3(x, y, z)
    sceneView.scene.rootNode.addChildNode(node)

    nodes.append(node)
}

where nodes was an array storing SCNNodes. Everything worked fine. If I had moved, the cones would have the exact positions as they had, a true "reality".

However, I purchased a nice 3D model of a zombie and I tried to change cones to the models. I found a solution of some sort and tried to implement it myself. This is what I came up with:

func addZombies(i:Int, x: Float, y: Float, z: Float)
{
    guard let zombieScene = SCNScene(named: "art.scnassets/StrongZombie.DAE") else { return }
    let zombieNode = SCNNode()
    let zombieSceneChildNodes = zombieScene.rootNode.childNodes

    for childNode in zombieSceneChildNodes
    {
        zombieNode.addChildNode(childNode)
    }

    zombieNode.position = SCNVector3(x, y, z)
    zombieNode.scale = SCNVector3(0.5, 0.5, 0.5)
    //zombieNode.look(at: (sceneView.pointOfView?.position)!)
    sceneView.scene.rootNode.addChildNode(zombieNode)

    nodes.append(zombieNode)
}

Unfortunately, even though it creates the zombies at the specific positions, if I move, the zombies "move" with me. They are displayed in relation to the moving camera which is undesirable for me. Can anyone help me out? I want them like the cones. Thx in advance

Clay Clay · Accepted Answer · 2017-12-22T05:10:13

With only seeing the limited code snippet....

I'm thinking it might have something to do with the default physicShape that is being approximated by the original DAE file. The shape can sometimes be overly complex and cause problems with the tracking.

Try setting the zombieNode physicBody to a standard box shape

let box = SCNBox(width:0.01, height: 0.01, length: 0.05, chamferRadius: 0.001)

zombieNode.physicsBody = SCNPhysicsBody(type: .dynamic, shape: SCNPhysicsShape(geometry:box))

Also set debugOptions to show the Physics shapes if you have not already done that. This will help with debugging wants going on with collisions as well.

sceneView.debugOptions = .showPhysicsShapes

How to add 3D models to a scene so that they have certain XYZ position?

2 Answers