Last night I successfully did something I wanted to plan : raymarching rendered through "portals". Neat trick : start the ray from the portal's surface instead of the camera, the marching will operate automatically as if stopping by the portal.
Note: I used iq's shape sample code for the actual raymarching, I'm not good enough to do my own for now, I'll tell you the moment where I'll have my own (and it'll look less pretty, I guess?)
The rotating chicken and the rotating duck are taking a nap, don't worry.