# Is it possible to create an "impossible" rooms in games?

Forgive me my lack of knowlegde, but for quite a long time I asked myself whether it was possible to create a continous game space that some player could walk inside and so on, that would be absolutely impossible in reality, e.g. you have a very small house that allows you to go around it to see all sides and the full dimensions, and then, when you enter, it is like a giant hall, without any loading screen or (internal) "model change" and so on.

I'm no game designer and I never needed to learn 3D-modelling, so I don't know what is possible and what isn't. And is this the same as Is the "impossible object" possible in computer graphics? this? Or is it just the same category, but not exactly the same question?

Thanks.

• can you better explain what do you mean by the impossible room? creating a continuous world is possible but I don't understand the second part where you can see all the dimensions ?? Nov 9, 2013 at 16:11
• Imagine, you have a house with one single room. You can walk all around the house and see it's dimensions, meaning: It is, lets assume, about 5*5m in size. And then you walk in and seamlessly — technically, but also in the gameplay — you stay in a room with like 200*200m. Nov 9, 2013 at 16:17
• I think you can do it with some work. You could perhaps use some similar techniques that this game uses: youtube.com/watch?v=rjPdXd1gmyQ Nov 9, 2013 at 16:41
• You can't make impossible happen. You can, however, make it seem like it happened.
– user15805
Nov 9, 2013 at 16:58
• As it stands, if you insist on contiguous space in the source data (and I have no idea why you're fixated on this restriction) your problem is unsolvable. Nov 9, 2013 at 19:47

You can play a lot of tricks with space using portals (the rendering kind) - see Prey, Portal, or Antichamber, for examples. In case you're not familiar with this concept, it's much more than simply teleporting the player around - the renderer actually lets you see through the portal, so it can be completely invisible if that's what you want. Antichamber in particular uses invisible portals extensively to create the illusion of "continuous" impossible spaces. Also see this Youtube tutorial for an example of the sort of thing that can be done.

In an engine with good portal support (such as UDK), a house that's bigger inside than outside is easily done by modeling the inside and outside in separate locations, and placing portals at each door and window to connect them.

• I don't agree with this. portals are just away to make him feel it's possible, what he is asking for isn't possible in 3D. Nov 9, 2013 at 19:03
• I agree with this post. If your engine doesn't natively support portals you can perform these types of tricks in various ways. Often it would involve using multiple cameras looking at different geometry composited together, e.g. use render to texture or depth masking. Using a technique like that I made a gate in the middle of a field which goes elsewhere, and could also do a Tardis-like effect as OP described. Nov 9, 2013 at 19:10
• @DavidCummins what you said is correct. Though his intentions was rendering something that isn't possible in 3D space, he wanted it to be physically there and not make it appear to happen. Nov 9, 2013 at 19:24
• @concept3d Well, clearly an impossible room is, uh, impossible in flat 3D space without tricks. The question is pretty trivial and boring if you interpret it that way. Much more interesting to consider space that is curved, or multiply-connected. Portals are just a convenient way of implementing such a space in a 3D engine. Sure, it makes it "appear" to happen rather than "actually" happen. But realistic rendering is entirely about making something appear to be there that's not actually there. Nov 9, 2013 at 20:49
• @concept3d Sure, you can (in principle) render a scene in a curved manifold by raytracing along geodesics or some such. But portals can be seen as implying a manifold as well - a flat manifold with boundaries (walls) and nontrivial connectivity. I think you are too hung up on seeing portals as "fake" and are missing the fact that they're just a rendering implementation detail. :) Nov 9, 2013 at 23:06

Is it possible to create a continuous game space?

Well, it is possible to make the player feel that he/she is walking in continuous space, by procedurally generating the world, but I don't think that "true" continuous is possible, since the memory/processing usage will not be possible at some point even if you are going to use memory and hard disk if you want to save your already generated world.

You have a very small house that allows you to go around it to see all sides and the full dimensions, and then, when you enter, it is like a giant hall.

This is not possible in 3D space math which is used in computer graphics. But I would say (only speculations) you might make the player "feel" something like this using Projective Geometry and by trying to draw (which will still happen in 3D ) something like Hyper Cubes.

• Actually the "bigger on the inside" room is completely possible in game. The doorway is a portal. Nov 9, 2013 at 16:58
• Well: I don't want any "portals". I want a seemless transition, without any kind of changes in the model, as I clearly stated in the first post. Nov 9, 2013 at 17:40
• @qwerty3000 Portals are seamless transitions. Nov 9, 2013 at 17:55
• @Byte56 from what I understand from his question, he didn't mean portals, what I understood is rendering his purely mathematical assumption in 3D, which isn't possible, that's why I mentioned the Hyper Cubes. Nov 9, 2013 at 19:02
• Yep, I think the question is certainly open to interpretation. Nov 9, 2013 at 19:32