3rd Person Camera in SceneKit

Question

I need to attach a SCNCamera to a SCNNode so that whenever the node (ball) moves, the camera follows it.

So far I managed to do it by constantly moving the camera when physics is updated, but its not very efficient and has some delay.

    func physicsWorld(world: SCNPhysicsWorld, didBeginContact contact: SCNPhysicsContact)
    {
        var cameraP = SCNVector3(x: ball.presentationNode().position.x, y: ball.presentationNode().position.y + 5, z: ball.presentationNode().position.z + 12)
        camera.constraints = nil
        camera.position = cameraP
        camera.constraints = [SCNLookAtConstraint(target: ball)]
    }

I read some information about SCNTransformationConstraint that could "attach" the camera to the node but I found no working example.

I can't just attach the camera to the node as I want to adjust the position of the camera.

Thanks.

Edit: (To Moustach)

I tried to do that using:

optional func renderer(_ renderer: SCNSceneRenderer, didSimulatePhysicsAtTime time: NSTimeInterval)
{
    println("called")
}

but I get an error saying: Extraneous '_' in parameter: 'rendered' has no keyword argument name

Edit 2 (working):

With Moustach's advice, we were able to make this work efficiently.

The camera position is now updated on:

func renderer(aRenderer: SCNSceneRenderer, didSimulatePhysicsAtTime time: NSTimeInterval)
{
    println("called")
}

Furthermore, a new SCNNode was created as a rootNode of the camera node to hold its position.

Setting up the camera now looks like this:

        let lookAtBallConstraint = SCNLookAtConstraint(target: ball)
        lookAtBallConstraint.gimbalLockEnabled = true

        let tempCam = SCNCamera()
        tempCam.zFar = 5000
        camera = SCNNode()
        camera.camera = tempCam
        camera.position = SCNVector3(x: 0, y: 0, z: 0)
        camera.constraints = [lookAtBallConstraint]

        cameraPosition = SCNNode()
        cameraPosition.position = SCNVector3(x: 0, y: 5, z: 12)
        cameraPosition.addChildNode(camera)

And now the camera moving function looks like this:

func renderer(aRenderer: SCNSceneRenderer, didSimulatePhysicsAtTime time: NSTimeInterval)
{
    var cameraP = SCNVector3(x: ball.presentationNode().position.x, y: ball.presentationNode().position.y + 5, z: ball.presentationNode().position.z + 12)
    cameraPosition.position = cameraP
}

Moustach Moustach · Accepted Answer · 2015-07-17T13:41:46

It seems you are adding a new constraint every time the ball touches anything, which probably happens a lot every frame!

Here's what you should do:

Move the constraint creation to somewhere it will be only set once, such as the init
Move the position update code to the renderer delegate so that it only get called once a frame, just after the physics have been calculated.

You should see a huge performance update!

Edit: try this

func renderer(aRenderer: SCNSceneRenderer, didSimulatePhysicsAtTime time: NSTimeInterval){
    println("called")
}

3rd Person Camera in SceneKit

1 Answers