FMP: Whiteboxing

I decided to have at least three separate scenes within a level. Since it's a Grimm's environment I can allow myself for a little bit of magic. My dream is to create a portal door that would take me from one location to another, while you're actually able to look through it. The best example is probably Portal series.

You open a portal, see right through it to a different location and just enter it. I found this article on Gamasutra.com, basically explaining the effect of teleportation. There is also a code but unfortunately it's written in Blitz3D which gives me absolutely nothing. I will keep looking although I doubt I will find anything.

Here's a quick whitebox of my first scene.

This is basically a walk through the forest. It will spawn near the lake with my protagonist waking up on the muddy bank. I shall consider dead bodies laying around as well.

On the other end there's a wooden shack - the place with a portal door.

 The wooden shack will be a witch's place. I want to resemble a candy house from Hansel and Gretel but perhaps in much darker version.