How to control the camera in VR mode?

Questions
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1

I tried to control the camera in vr mode, such as changing the position of the camera. But the camera does not seem to be controlled in vr mode.For example,I want to do that:
function render() { camera.position.z+=0.01; renderer.render( scene, camera); }

I also try that var user = new THREE.Group(); user.add( camera ); ,but there was an error caught TypeError: Cannot read property ‘add’ of undefined

2

but there was an error caught TypeError: Cannot read property ‘add’ of undefined

Please demonstrate this issue with a live example. Otherwise it’s hard to say what’s going wrong. In general, if the camera has a parent object, the parent’s transformation should be respected by WebVRManager. Note that directly changing the transformation of the camera has no effect since it will be overwritten in VR mode.