Rotate SCNNode if user tap on any child node it will point towards camera

Question

Sorry If my question is silly I am new in SceneKit. I have added a globe using SCNnode sphere and added pins as a child node for that sphere. Now when user tap on any child node I want to rotate globe to such angle that my child node will come toward center for camera. Thanks in advance

Answer 1

If I'm understanding correctly, tap on any child and the globe rotates such that it faces you. I "think" you can do it this way.

Provided you have placed your child nodes accurately and they are pointing away from the center, then have lookat constraints on all of your children but set them to empty. Once one is clicked, set the lookat constraint on that child node and point it at the camera node.

func setTarget()
    {
        node.constraints = []
        let vConstraint = SCNLookAtConstraint(target: targetNode)
        vConstraint.isGimbalLockEnabled = true
        node.constraints = [vConstraint]
    }

The more difficult part may be to make sure your child nodes are actually facing away from the center because it will matter. IE: Poke a pencil in a ball and rotate it in your hand. The point of the pencil matters because it's glued to your parent object exactly how you placed it initially. If it was facing the center point of your globe for example, then you'd get the opposite effect.

One way to test it is to create the child nodes with a pointer - in this case, it's just a turret from one of my games.

let BoxGeometry = SCNBox(width: 0.8, height: 0.8, length: 0.8, chamferRadius: 0.0)
            let vNode = SCNNode(geometry: BoxGeometry)
            BoxGeometry.materials = setDefenseTextures(vGameType: vGameType)
            
            let tubeGeometry = SCNTube(innerRadius: 0.03, outerRadius: 0.05, height: 0.9)
            let fireTube = SCNNode(geometry: tubeGeometry)
            tubeGeometry.firstMaterial?.diffuse.contents  = data.getTextureColor(vTheme: 0, vTextureType: .barrelColor)
            
            fireTube.position = SCNVector3(0, 0.2, -0.3)
            let vRotateX = SCNAction.rotateBy(x: CGFloat(Float(GLKMathDegreesToRadians(-90))), y: 0, z: 0, duration: 0)
            fireTube.runAction(vRotateX)
            vNode.addChildNode(fireTube)

Once you have placed these on your globe and they are rotated correctly, setting lookat constraints "should" work. It should look kind of like a pin cushion (sorry, only example I can think of), and then your globe should rotate towards the camera.

Hopefully