I've never heard of any Quake 3 mods that have used anything like a portal gun, but it would be possible.
The first problem would be the actual code for the portal gun and the entity of the portable portal - I'm not sure if you've ever played Gmod, but outside of the game Portal, all the other attempts at putting it into existing mods were really bad and the portal entity created a lot of lag. In Portal they fixed most of those problems with the HL2 engine, but the game is still more resource demanding than Quake 3. Have you ever played on an unlimited bp server? It would lag like that.
The second thing is the tremulous aspect of it. Why would anyone want portals on tremulous? I could see wanting to plant cameras and stuff, that's a nice thing that can be done. Portals in any multiplayer team game would be extremely confusing. People memorize maps so they don't have to deal with others teleporting up behind them, it would ruin the game for many.
What you need to think out before anyone would probably consider wanting this:
- How would it be implemented? How would non-backported clients handle it?
- How would you stop people from hacking at the code and using it to teleport away when they have 4 hp?
- How would teammates interface with your portal?
- How would you identify your own portal?
- How would you identify an enemy portal?
- Can your teammates use your portal?
- Can the enemy use your portal?
- Can you get telefragged if your portal sends you into another player or a building?
- Can objects such as grenades go through the portal? (like in Quake 4)
- Can you destroy someone's portal?
- How does a dretch create a portal?
- How would you stop people from using the portal to glitch outside of the map?
- How much would you pay me to help you with this?
what everyone seems to forget, is that this isnt meant for normal gameplay, its only a little fun mod that isnt meant to be balanced
to tinman:
- How would it be implemented? How would non-backported clients handle it? like any other mod..
- How would you stop people from hacking at the code and using it to teleport away when they have 4 hp? creating another portal will remove both previous portals if the second portal is the third one made
- How would teammates interface with your portal? walk through it..
- How would you identify your own portal? you will have your name above the portal
- How would you identify an enemy portal? there will be team coloring(humans blue, aliens red) with the names
- Can your teammates use your portal? yes
- Can the enemy use your portal? yes
- Can you get telefragged if your portal sends you into another player or a building? yes
- Can objects such as grenades go through the portal? (like in Quake 4) no, only players
- Can you destroy someone's portal? no, they can only be reset
- How does a dretch create a portal? they dont
- How would you stop people from using the portal to glitch outside of the map? if you could explain how a player WOULD id tell you how
- How much would you pay me to help you with this? 9000 bubble dollars(gay ass spongebob joke)
i am also thinking of a living time for the portals...maybe they disappear after 10 secs?
i also forgot to add, once someone that can model(

hi you sexy modelers) wants to help me, ill work on the code. no use in working on a untimatly unfinished project with busted models right?