If a portal based game engine was made, then instead of measuring an objects location by where it is relative to the worlds origin, you could measure it relative to the current room that object is in. Limiting an objects movement through the world to the current room it's in and any portals linked to that room would allow the object to move around as in any other game, except for one key extra - the rooms can freely overlap, allowing objects to share the same 3D location (Relative to world origin), but because they are in different roomss they can't see or touch each other.

For example, you could create a coridoor that never ends - link each end of the corridor to each other, so as you walk off one end you appear at the other. You could create a room with a pillar in the middle, but as you walk round the pillar you move through a portal and into another copy of the room, making the door you came in from vanish until you wander round the other way. You could make a skyscraper which you can enter, go up to the top floor, open a door, and be greeted by a green field stretching off to the horizon, which you can safely walk onto without plummeting to your doom. You could even create a portal in the ceiling, which provides a view of another rooms floor - allowing people to effectively walk across the ceiling.

Drawing a world like this isn't too hard; for the room the camera is in, you would use the portal list to work out which other rooms you can see, and use clipping planes set up along the edge of the portal to cut out any bits which are hidden from view (To prevent them intersecting other portals which overlap in 3D space, e.g. two doorways which lead out to two different fields). Obviously you would have to be careful with how many rooms you draw, especially with infinite length coridoors!

This type of engine could be put to use in horror/surreal games, where things aren't always the same if you were to visit them again - e.g. you're trying to run away from someone but every door you open leads to the room with them in

No, not 4D the games company, but games which delve into the fourth dimension.

What? Like Time?

If a portal based game engine was made, then instead of measuring an objects location by where it is relative to the worlds origin, you could measure it relative to the current room that object is in. Limiting an objects movement through the world to the current room it's in and any portals linked to that room would allow the object to move around as in any other game, except for one key extra - the rooms can freely overlap, allowing objects to share the same 3D location (Relative to world origin), but because they are in different roomss they can't see or touch each other.

Alternatively you could have two parallel worlds, separate but with the same room layout but different objects in it. Possibly easier to integrate into your standard engine as well.

For example, you could create a coridoor that never ends - link each end of the corridor to each other, so as you walk off one end you appear at the other.

You could probably hack this in a standard portal engine anyway. Each portal has to link to somewhere - all you have to do is make the two "ends" of the corridor link to each other.

This type of engine could be put to use in horror/surreal games, where things aren't always the same if you were to visit them again - e.g. you're trying to run away from someone but every door you open leads to the room with them in

I'm not convinced you need loads of custom support for all this but I seriously like your ideas

What? Like Time?

Personally, I don't believe in time travel

At one point I was thinking of making a program to examine what a fourth dimension (As in an extra axis of movement) would be like, by ray casting a 4D object into a 3D grid, then displaying that on screen. Have you ever wondered what a 4D cube or sphere would look like? They're mathematically simple, so would be very easy to convert into 4D. As long as you deal with the maths instead of visualising a fourth dimension in your head, you won't go crazy

I'm not convinced you need loads of custom support for all this but I seriously like your ideas

Custom support = more flexibility

I think you'd need two transformation matricies for each link - one to apply to the graphics, and one to apply to objects as they pass through the link.

If I had a good idea for a game to make using it, I might persue it further...

Personally, I don't believe in time travel

Maybe so, but time is often thought of as the 4th dimension

At one point I was thinking of making a program to examine what a fourth dimension (As in an extra axis of movement) would be like, by ray casting a 4D object into a 3D grid, then displaying that on screen. Have you ever wondered what a 4D cube or sphere would look like? They're mathematically simple, so would be very easy to convert into 4D. As long as you deal with the maths instead of visualising a fourth dimension in your head, you won't go crazy

Wasn't there an old desktop program which did this? it displayed a klein bottle or something. Also my linux screen saver does it from time to time - it's bizarre.

I'm not convinced you need loads of custom support for all this but I seriously like your ideas

I think you'd need two transformation matricies for each link - one to apply to the graphics, and one to apply to objects as they pass through the link.

Do you mean that the matrix which is applied to objects is used to perform some sort of wierd effect?

I think you'd need two transformation matricies for each link - one to apply to the graphics, and one to apply to objects as they pass through the link.

Do you mean that the matrix which is applied to objects is used to perform some sort of wierd effect?

All I can think of it being used for would be re-positioning the object so it's in the right place in the new room. A seperate rotation value can be applied to any direction/velocity it has. If you were to send multiple points through the matrix, then technically you could do things like shrink/enlarge the object as it passes through...

All I can think of it being used for would be re-positioning the object so it's in the right place in the new room.

Surely you just set the objects position and transform as normal?

A seperate rotation value can be applied to any direction/velocity it has. If you were to send multiple points through the matrix, then technically you could do things like shrink/enlarge the object as it passes through...

Or you could apply a scaling matrix to your standard transformation matrix.