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Questions tagged [portals]

a doorway or opening that connects two areas of the game space, even if those areas aren't adjacent & aligned in the physical layout of the environment. Players can typically see and move through the portal into the linked space. Portals were most famously used in the Valve's Portal game series, where the player can shoot linked portals onto various surfaces and traverse between them to solve puzzles.

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5 votes
1 answer
113 views

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

I'm trying to follow This tutorial for a portal mask shader. It's an awesome effect but it comes with a couple of caveats. The shader as he designs it can only exist in a bubble, as: The portal is ...
1 vote
0 answers
47 views

How to reduce required memory when collecting cells in a portal engine that represent open areas?

My engine is based on Cells and Portals. From the Current Cell, I traverse the portals recursively. While doing so, I cache the clipping rect. When rendering the cells, I use the cached clipping rect ...
0 votes
1 answer
90 views

Align Relative Portal Camera Position

I've been having a bit of trouble with this small piece of code. To set my relative PortalCam position, I first take the distance and angle from the Portal and Player Cam. Then apply the distance and ...
3 votes
2 answers
2k views

Impossible rooms in 3D games

recently I was playing The Stanley Parable, and noticed that there are several impossible spaces in the game - in this example, a pair of pillars in the middle of the room, which from each side appear ...
0 votes
1 answer
105 views

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

My engine consists of Rooms. Rooms are connected via Portals. Items have a roomNumber field to indicate which room they belong to. And rooms have a linked list of ...
1 vote
0 answers
145 views

How can I reduce a frustum to the subset that passes through a portal AABB?

I'm trying to implement portal based occlusion culling: There are sectors and portals. When a portal is visible, the sector it is connected to is rendered. The sector is made of polygons and ...
0 votes
0 answers
67 views

Portal physics by bending space

I've been thinking about how to implement a portal, and after a quick search, everyone seems to do it by adding a camera per portal and then just update the other portal's view with that camera's view....
10 votes
1 answer
9k views

How to create high quality and fast portal effect?

EDIT: So I've gotten the portal visual effect working with no performance hit, and I've got the physics set up of objects with rigidbodies moving through portals seamlessly, and objects with character ...
2 votes
1 answer
373 views

representing transforms without a world/global reference frame

Background: I'm trying to make a segmented/portal-based game engine that supports impossible (non-euclidean?) geometry. By segmented/portal-based I mean the world is divided into segments which are ...
1 vote
0 answers
195 views

Recreating A Puzzle Effect Using Stencils

I'm trying to recreate something I saw on reddit a while back. I tried rendering camera output onto planes, but am not getting the results that I want -- this is basically what I'm trying to recreate: ...
6 votes
1 answer
3k views

How does a segment-based rendering engine (as in Descent) work?

As far as I know Descent was one of the first games that featured a fully 3D environment, and it used a segment based rendering engine. Its levels are built from cubic segments (these cubes may be ...
9 votes
2 answers
1k views

Is there anything equivalent to Portal 2's linked_portal_door in any other engines? [closed]

I need the functionality of the linked_portal_door that's in Portal 2. I've searched a little in UDK and mostly got people trying to duplicate the portal gun. Does anyone know if UDK, CryEngine, ...
1 vote
0 answers
934 views

Rendering portals using stencil buffer

Due to this question I have changed the method of rendering portals. Before I was using FBO and rendering to a texture, but somehow I failed. Now I switched to a stencil buffer method. My problem is ...
6 votes
1 answer
915 views

With what projection matrix should I render a portal to a texture?

I'm using OpenGL. I have problem with my engine's portal implementation. To create the first portal I do: create a virtual camera with the position of the second portal and the correct orientation ...
4 votes
1 answer
213 views

portal cutoff effect

I want a 3D Mesh to come out of a flat portal. Only the part of the mesh that's coming out of the portal should be rendered, so the mesh should be cut off or sliced until it's fully outside the portal....
3 votes
0 answers
2k views

Pathfinding with portals? [closed]

I'm not making a game with portals in it (one way or bidirectional). These portals instantly teleport characters from one location to another. How would I implement pathfinding? Here's an animation ...
19 votes
2 answers
7k views

How to blend two cameras when traveling through a portal in Unity3D

Before I get to my question, I know the most obvious solution would be to use the normalized view port rect, however I need more complex shapes than a rectangle, and I've looked in to using the view ...
3 votes
1 answer
315 views

How Do Objects Not Clip Out the Back of Thin Walls When Put Through a Portal?

In Portal or Portal 2, let's say you pick up a cube and put it most of the way through a portal on a very thin wall. The cube should clip outside the backside of the wall. How does Portal do this, or ...
12 votes
3 answers
2k views

How to implement collision detection of portals?

For example, take this scenario (excuse my horrible drawing skills): This is based on "Portal", where the stickman is going through the blue portal (which is linked to the red portal), but there is a ...