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6 votes

Impossible rooms in 3D games

For engines without native portal features, these types of spaces are usually created using invisible teleportation volumes. The level author creates two or more exact copies of the area, with subtle ...
DMGregory's user avatar
  • 135k
3 votes

Impossible rooms in 3D games

Stanley Parable runs on the Source engine, which is a portal-based engine. In a portal-based engine, not all sections of the game exist in the same 3d space. Every zone (room) has its own 3d space ...
Philipp's user avatar
  • 120k
2 votes

representing transforms without a world/global reference frame

You do not need to have multiple reference frames in order to support portals. You mentioned Duke Nukem 3D as the kind of portal system you want. That game fakes 3D using a technique called Sector-...
congusbongus's user avatar
  • 14.8k
1 vote

How can I hide the interior frontfaces of a portal when viewed from the outside?

A simple trick for this is to add a second shader pass, or second material that renders before the main one. Switch the culling mode to cull front faces and draw back faces instead. Write to the depth ...
DMGregory's user avatar
  • 135k
1 vote

In a portal-based engine where Items are owned by a room, how to do inter-room collision detection?

The naive approach would be to do collision detection by not just querying the room but also the adjacent rooms, but this does not cover the case that an item might be so large that it passes through ...
Philipp's user avatar
  • 120k

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