Game Physics

[chriso20]

Lets say i put a grenade under the left foot of a guy in a game with physics, he goes flying up in the air and lands in a heap.
REPEAT; surely if you put the same grenade under the same foot at the same point, under the same guy in the same area, then he should fly away exactly the same?

Unless the grenade has something to make it explode in random directions or more so on one side.


I mean you have a perfect sphere of explosion, the foot thinks, right i weigh 1kg, the blast is 10cm away, its 1000newtons in strength. Overall = 1x10x1000=10,000Newtons in (triangulate point on grenade and point on foot) this direction, -gravity etc.....

Surely it'l come up with the same answer everytime?


I'm mentioning this because someone said something about "blah blah" and gabe said, "this'd have to be scripted as the physics is random" (or words to that effect).

But surely if u want a guy to land with his arm over a railroad track (for example) then you just trial it over and over til u find the right place for him to go boom. This'd b a lot more realistic than scripting, although th whole point of physics is to be random and different, however the alternative script is also exactly the same.


(and i know i sed surely a lot lol)

 

[Roland Deschain]

It's physics engine, so if all the initial conditions are the same, then the guy will fly in the same direction and manner. Of course, all Valve has to do is randomize the exploding pattern and you get different scenarios.

 

[Platinum]

...? whatttT?!?!?!

 

[Cole]

Theres no such thing as random.not even in life.

 

[Maui]

Theres no such thing as random.not even in life.

Do a google on "quantum theory" :/

EDIT: and "Schrodinger's cat"

 

[JimmehH]

Not only do you have the force of the explosion, but you have the momentum of the person being blown up to take into account and various other things.

Basically, if the variables were all the same, then yes, they would fly away exactly the same each time which I think is what Gabe means by scripting it. What you describe is a long and drawn-out way of scripting too.

Theres no such thing as random.not even in life.

Radioactive decay is. Although you're technically right about there being no such thing as random on a computer I think.

 

[iamaelephant]

Well if you really wanted the same thing ot happen every time, why not script it?

 

[Roland Deschain]

Theres no such thing as random.not even in life.

Schroedinger cough cough, his theory even ****ed up Einstein, that's why Einstein sayed that he can't believe God is playing dice with the universe (or something close to it).

Basicly schroedinger sayed that if you cannot know the position and velocity at the same time. One of them always is unknown and can only be approximated through probability.

 

[JimmehH]

I think it was Heisenberg who said it first.

In fact, the cat is an example that Schrodinger came up with to demonstrate how ridiculous the theory is.

 

[marksmanHL2 :)]

Heheh this is a funny convosation.


Let me enlighten you all!

Valve said (Fact) that the physics wont allways be the same because of the way some of the interactions are very slightly random. If you looks at the orriginal AVI footage of E3 from 2003 you will see things behave slightly differently than to that in the bink videos. Thats because they re recorded it from the game engine to make the new resolution vids.



Basically, the physica are extremely accurate. But there are SOME random things happening all the time. Also, take note that physics in multiplayer might be even more random to increase performace. :thumbs:

 

[GuNzABlaZiN]

I read an interview where Gabe said that he was doing the exact same thing to a barrel and it wouldn't always have the same effects.

 

[Vordrax]

First post

Anyways, Newell said that the physics engine isn't 100% deterministic, so as to cut down on the processor cycles. There is a random seed in it, probably based on time.
However, he said that the level designer could put his own random seed into it to ensure the same results.
Hope that helps you

And now, imu. :imu:

 

[Vegeta897]

So basically what we have come to see is that Valve has added some random factor to the physics engine, to produce different results. This is good, because in certain parts in the game where an explosion (for example) always happens in a scripted spot, the effects will be different each time you play through tha part of the game.

 

[Hazar]

Hello and Welcome Vordrax!


Anyway, I suppose there won't be any wind in HL2 - too much processing power.

 

[Vegeta897]

Hello and Welcome Vordrax!


Anyway, I suppose there won't be any wind in HL2 - too much processing power.

Actually, no. If you mean wind by actualy air particles pushing objects, then ofcourse that won't be in the game.

But you can easily do simple wind effects. Like in the beginning when Gordon gets off the train, you see scripted wind blowing some trash along.

Valve even said that made a cyclone that actually blew objects around and sucked 'em up.

But it's not gonna be like, if I knock down a large sheet of metal it will create wind, that would be like I said earlier, physical air particles.

 

[FictiousWill]

Pedantic random number bashers aside, the physics have a random element. You will never get an exact duplication of a physics-powered event.

 

[Brian Damage]

But it's not gonna be like, if I knock down a large sheet of metal it will create wind, that would be like I said earlier, physical air particles.

Actually, that could probably be done by checking to see which way the metal was falling, then creating a weak spherical field of force in that direction while the metal is in motion. Particle simulation doesn't have to come into it.