Simple portal demo implemented with ARKit+SceneKit, the trick is to change the rendering order and render invisible "masks" to hide what's inside.
Licensed under the Apache License, Version 2.0
You can use this code anyway you like, but please provide attribution.
The slipperystonework texture is from freepbr.com
The environment.jpg/environment_blur.exr is from Apple demo
Bjarne Lundgren / bjarne@sent.com / @bjarnel