After half an hour I finaly found free openscenegraph documentation. Everything else had the label free on it only to redirect me to a cart demanding 28$ from me (which in my opinion is a very questionable sales tactic).
Working on glPortal2 I think a lot about how I am going to build a teleportation device (for the game of course).
For obvious reasons (scientists wanting to build a teleporter) there are a lot of publications on the topic.
At the moment the very little code there is uses glfw. Though now I am considering using SDL or Ogre, while the game is still young and flexible.
Do you have any preference? Which framework do you think would be best to implement glPortal2 with? Please elaborate.