Gaze at SCNNode using SceneKit and CoreMotion

Question

I'm creating a Virtual Reality application using SceneKit and CoreMotion. Everything is working fine, but now I'd like to write a function to check if a user is looking at object by calculating where the object is in eye-space.

I'm using SCNSceneRendererDelegate to delegate the renderer function in my ViewController

func renderer(aRenderer: SCNSceneRenderer, updateAtTime time: NSTimeInterval) {

    var motion = motionManager?.deviceMotion

    if (motion != nil) {
        let currentAttitude = motion!.attitude
        let roll = Float(currentAttitude.roll)
        let pitch = Float(currentAttitude.pitch)
        let yaw = Float(currentAttitude.yaw)

        cameraRollNode.eulerAngles = SCNVector3Make(roll, 0.0, 0.0)
        cameraPitchNode.eulerAngles = SCNVector3Make(0.0, 0.0, pitch)
        cameraYawNode.eulerAngles = SCNVector3Make(0.0, yaw, 0.0)        }
}

I wrote the following code in Android (which supports the official Cardboard SDK).

private boolean isLookingAtObject(WorldObject object) {
    float[] initVec = { 0, 0, 0, 1.0f };
    float[] objPositionVec = new float[4];

    // Convert object space to camera space. Use the headView from onNewFrame.
    Matrix.multiplyMM(mModelView, 0, this.getHeadViewMatrix(), 0, object.getModel().getModelMatrix().getFloatValues(), 0);
    Matrix.multiplyMV(objPositionVec, 0, mModelView, 0, initVec, 0);

    float pitch = (float) Math.atan2(objPositionVec[1], -objPositionVec[2]);
    float yaw = (float) Math.atan2(objPositionVec[0], -objPositionVec[2]);

    return Math.abs(pitch) < PITCH_LIMIT && Math.abs(yaw) < YAW_LIMIT;
}

Is there a way to calculate the object in eye-space using CoreMotion and SceneKit

Answer 1

If all you're looking for is whether an object is in view, you don't need to do any coordinate conversion math yourself. Just ask the view — there's a method for that .