Friday, July 07, 2006

Warning! Game Related Blog - Prey Physics

This post is about the use of theoretical physics in the science fiction shooting game Prey. Don't get me wrong, Prey is not an ideal game; it's stupid, bloody and enormously derivative in everything it does, from combat, to weapon selection, to the plot. That said, it raises some questions about physics and biology that are quite interesting and worth exploring. I know I don't normally talk about games, mainly due to a desire to maintain the work-life separation but a conversation with Steve Hogarty of PC Zone intrigued me enough to write this.

Prey - upside

First off, its wall-walking technology is interesting. Simply put, there are powered ramps on the walls which, when you walk onto them, flip your perspective around so you're like a fly walking up the wall, and gravity is apparently always perpendicular to you. It's not possible that you're just stuck by your feet, as your legs wouldn't be able to cope with your entire body weight shifting from the vertical to the horizontal to the inverted vertical, whilst running and shooting; you'd fall over at the knees and just hang there.

So there must be a field covering the entire walkway to hold you in place. However, when a hunter is killed on an upside-down walkway he immediately falls off (likewise if you jump), indicating that the point of contact is only at the base of the foot, or that the field only maintains strength as long as you're in contact with it (like the giant Antaeus from the myth of Heracles only maintaining his tremendous strength so long as he was in contact with the ground.) Still, if you jump into the walkway, it doesn't grab you back by that part of your body, so it can't be a mere contact thing. Nor are you wearing special boots or anything of the sort.

Prey - portalfeet

The portals are extremely problematic. These consist of two linked holes, allowing you to move anywhere on the level. While wormholes are theoretically possible, there are multiple problems with these as they are expressed here. Firstly, they should cast shadows if they allow light to pass through their entrances - and they allow you to see people through the portal entrance, so light does pass through. However, if they don't allow light to pass through, they should be black circles on the side you can enter through, and be perfectly transparent from the back. These portals allow light to pass through the entrance side, so you can see into them, and are perfectly transparent from the back. This doubles light, effectively creating it. With this system, you could place one entrance to a portal behind the other, so the light passing through the back of one would be endlessly be recycled, growing in strength exponentially, creating limitless energy from nothing - which counteracts the first law of thermodynamics.

Secondly, there are problems with what is allowed to pass through the holes. Light and sound seemingly can, but gravity cannot. Whether other electromagnetic waves can isn't clear - your shots, which vary from pure energy to projectiles, can pass through. The other key forces to the universe (the nuclear forces, etc) seem to be unaffected. Perversely, the light from your lighter cannot pass through the portal either.

Thirdly, approaching the portal from the side or rear. If you walked into the back of the portal, then backed off, would the intruding piece of your body simply shear off? If not, how does the portal qualify what is a full entity and distinguish it? Approaching if from the side would surely shear the entity along the line of approach, like the finest nanowire. Unless, of course, the edges of the portal are robust and solid in themselves - which they're ostensibly not.

And what if someone walks through the back of a portal while someone else is exiting it? Would they appear on the same spot? Would they mingle? If you force that many atoms into the same space, surely they'd explode. What if you poked your finger into a mirrored portal - one that the surface for entrance and exit are the same? Surely you'd be able to touch yourself, much like you can in normal life, albeit in a mirrored form. In crude terms, you could give yourself a reach-around!

Finally, the portals seem to float above whatever surface they're fixed to. We have to assume they're held in place by magnetic fields or something like that, as if they weren't imagine the problems - dropping a portal onto the surface of a planet would result in it spewing out a tube of material at its other end, as gravity sucked it down, endlessly consuming until it hit the planet's centre.

There's a lot more problems with the physics of Prey and they simply haven't thought the issues through at all. They make for a fascinating physics test of the rigours of science fiction, which is more interesting that the game itself.

Prey - manpants

I can't justify this though.

7 comments:

Jon said...

I don't think a game that enables you to turn into a ghost on a whim, live forever by shooting red-and-blue carnival decorations, or physically combines the ideas its stealing really had much of a grounding in theoretical physics. Given the overall coherence, it's a marvel they're even called "portals".

grilly said...

i love how much you care.xx

Grill said...

It did have a grounding in theoretical physics, or at least it's elder, lackadaisical, brother hard sci-fi - the Dyson sphere, though hardly featured, is hard sci-fi, the concept of wormholes is theoretical physics, wall-walking is plausible, just it has problems how they do it. It's an interesting thought problem pointing out the ways it should work though. Carnival decorations aren't particularly sci-fi TBH.

grilly said...

how watertight does theoretical physics have to be? theoretical surely means fictional, otherwise it would be actual physics, right? so can one label any black box invention 'theoretical physics' even if it breaks the laws of reality, like calvin and hobbes' transmogryphier?

Neil said...

I’m not sure whether to defend or attack prey for the blatant oversights in its game mechanics. Part of me just wants to shout ‘it’s just a game!’ but well spotted Grill the walkway and portal physics oversights are frankly shit, much like the game, the best part of which is the jukebox at the start. Being abducted to the Blue Oyster Cult is quite special

Grill said...

I even thought the music was shit TBH. This took ten years? :-0

neil said...

I've stopped playing, despite the problems with the reality of the physics, it mostly a very dull FPS.

This looks much better:
http://video.google.com/videoplay?docid=7844987544204140976&q=interview+prey