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Examining Portal's Teleportation Code
Gamasutra is running a story deconstructing the mechanics of Portal's teleportation programming. They present a snippet of Portal's code and a downloadable demo. They ran another article in this series earlier this year with an analysis Mario Galaxy's unique take on physics. We've discussed the development of Portal in the past.
"Teleport mechanics in video games are nothing new. Puzzles from the original Gauntlet were memorable -- and more than likely, that wasn't the first game to use teleportation as a gameplay mechanic. The difference between Portal and all those that came before it is that Portal's teleportation acts as a frictionless tube between point A and point B. Physics are still hard at work inside the frictionless tube. Instead of simply repositioning an object from point A to point B, the player enters point A with full velocity and exits point B with the same speed, but moving in a new direction."
Update: 8/26 at 19:37 by SS: Dan notes that the code was not directly from Portal; it was written to approximate Portal's physics.
Your mom has a frictionless tube.
First post?
But... can they telefrag?
I just love the sound of 2 bodies trying to occupy the same space at the same time in the morning... or afternoon... or evening...
Don't blame me, I voted for Kodos
>>Physics are still hard at work inside the frictionless tube. Instead of simply repositioning an object from point A to point B, the player enters point A with full velocity and exits point B with the same speed, but moving in a new direction."
Should be "Speedy thing goes in; speedy thing comes out."
Duke Nukem 3D's teleporters would teleport your weapon shots, too.
I loved shooting the rocket launcher into it only to hear a buddy die on the other side of the map as the rocket appeared and continued on its way.
I don't recall if you jumped into the teleporter if you'd exit and continue your jump arc, but there is precident for "movement in progress" teleportation.
(-1: Post disagrees with my already-settled worldview) is not a valid mod option.
The difference between Portal and all those that came before it is that Portal's teleportation acts as a frictionless tube between point A and point B. Physics are still hard at work inside the frictionless tube. Instead of simply repositioning an object from point A to point B, the player enters point A with full velocity and exits point B with the same speed, but moving in a new direction.
Are you fucking kidding? What's not completely obvious about this algorithm that should be Slashdot-front page worthy? I mean, it's fucking mind blowingly obvious, of course it keeps the velocity and translates it, how else could it do what it does? I can understand why it would be relevant to do a coding tutorial on the subject, but that's about as newsworthy as a Bresenham line drawing algorithm tutorial. TFS looks just like a "hey let's talk about how some super popular game is super awesome and post about it on a high traffic website".
You just got troll'd!
The grits are a lie :(
In the game, GlaDOS says "momentum is conserved through the portal." Assuming our physical system is the character, momentum definitely is not conserved. Neither is energy. The description "the player enters point A with full velocity and exits point B with the same speed, but moving in a new direction" is exactly correct: a textbook example of momentum non-conservation. However, what drives the exciting "flinging" effect, which makes Portal's teleportation so unique, isn't just momentum redirection. It's that you instantly obtain the potential energy of your exit location. This new potential energy can be converted back into kinetic energy, increasing your speed...mix in a little momentum redirection at the portals then wash, rinse, repeat. Although GlaDOS describes the game physics incorrectly, there is a game walkthrough where the programmers do describe it correctly. If you take any physics courses from me, you can expect to see some Portal questions on future quizzes :) Nice article overall.
i\hbar\dot{\psi}=\hat{H}\psi
I'm not a portal porter
I'm a portal porter's son
And i'm only porting portal
Till the portal porter comes
Portal's physics go *way* beyond what the article implies.
Article basically says: it's not a simple teleport, direction of movement and momentum are preserved.
This is far too much of an oversimplification. Portal was probably a technically difficult game to code for - mostly due to collision physics. The problem is that something does not instantly teleport from one end of the portal to another. You can have an object on BOTH sides of the portal. This makes physics calculations very difficult, since you essentially have a single object of a small finite size, colliding with different objects across the room, affected differently by gravity, etc.
If I get the right gist from the developer commentary in the game, their solution was the CLONE the two sides of the portal in a mini physics-only environment and run the simulation there.
Definitely much more complex than the article.