Collisions

[Botsareus]

ok , I just tryed the F1 mode , I found some more bugs , but my bots make it , They do make it anyway , few....

[PurpleYouko]

But if the new legues will use this new , slow , collisions ,then I have no choise , I will use them too.

What actually happens now (V2.36) is that when a collision is detected the two robots are moved (not accelerated) directly away from each other such that they don't overlap.
Next, the incoming momentum of both robots in both x and y directions is calculated.
Then the combined momentum is divided between the two robots in proportion to their mass so that a huge fat robot hitting a tiny one will just be slowed a little while the tiny one will be accelerated away from the impact quite a lot.

A collision like this (more arrows = more speed)

O>>>>>o>

will result in

O>>>o>>>>>>>>>>

and

O>>>><<o

will yield

O>o>>>>>>>>>>>>

Make sense now?

[PurpleYouko]

Previously any collision resulted in both robots being accelerated away from the impact by an amount proportional to the degree of overlap.

This just wasn't realistic as a large overlap could sometimes happen at low speeds while a small overlap could equally happen at high speeds.

[Botsareus]

ok , thx,  now it makes sense.

[Zelos]

it is ALLWAYS, ask any physicer about it. it you throw a ball and then it bounce at a wall. to wall get some momentum and goes at the other way, or maybe its the air that get the momentum, did you ever think on that air can get it?. and if I start whit 3m/s then something else have -3 compared to me. it is coz the momentum in the universe always shall be 0, that spacecrafts worx. if it wasent so we wouldnt be able to go anywhere in space.

[Numsgil]

t is coz the momentum in the universe always shall be 0,

Momentum of the universe is undefinable:

Momentum of Universe.

Wikipedia also says:

However, in curved spacetime which is not asymptotically Minkowski, momentum isn't defined at all.

the momentum in a system is always 0

no matter what you do, it will always be 0

Momentum for any system is defined as:

Sum of (mass_x * velocity_x)

Say I define a system with 1 mass and 1 velocity.  A ball 2 kg moving at 5 m/s.  In my system, total momentum is not 0, but 10.

Therefor, for my system, momentum is not zero.

Now, is Momentum always conserved?  Yes, assuming it's definable (see above).  That means that taken any system. the change in momentum for the system will be zero.  That assumes you take everything into account, and that you have a way to measure micro velocity.

PY's examply describes how and why Kinetic Energy is not conserved.  That's because KE is a form of energy.  Energy itself is conserved.

But the big question: is momentum itself always zero?  Most certainly not.  Shame on you for even thinking such a thing!

[Numsgil]

Imagine the universe is not expanding.  That's not hard, you've done it already.

Imagine I am moving 5 m/s relative to the universe.  Now imagine I define the universe as everything except me.  The momentum of the universe would be 5m/s times its mass.  Definately not 0.

Because velocity is a relative term, the quantity of momentum isn't important.  Only the change in momentum is important.

[PurpleYouko]

You are correct that the atoms in the air or water or whatever medium a moving object is in, will take on some of the momentum as the object slows but then again we aren't attempting to model every atom of the whole universe here. All we care about are collisions between balls of varying size and mass.

My whole poiint is and always has been, that it makes more sense to model Darwinbots physics on momentum rather than KE.
For one thing, momentum has a vector while KE doesn't (it actually can but it is harder to define)
It also gets a bit tricky to split KE into X and Y coordinate vectors while for momentum it is trivial.

Basicly I am just too lazy to work out the math for using KE so I substitute momentum instead.

Incidentally though, how do you explain that the universe is not only expanding but accelerating?
How does that fit in with your idea of zero momentum?
Where is the extra velocity coming from?

Come to that, how do you know that the big bang wasn't already moving at the point of exploding into a new universe? If it had been then the universe will have a significant bias in momentum in one direction so the total combined momentum in the system will definitely not be zero.
Besides which it is impossible to find a position of rest with which to compare motion so the toatal momentum of the entire system is inherantly unknown and unknowable.
You are the one who keeps going on about relativity. Check your facts before making sweeping statements that can never be proven under the physical laws that you yourself advocate.

[Endy]

Would it be possible to have a collisionless mode? Not exactly realistic, but the speed would be unreal. :D


Endy B)

[Numsgil]

Actually collisions have been so streamlined you'd only get like another 20% increase in speed.

But it might be worth a go.  An interesting mode to be sure.

A much faster and pointless mode would be a 'blind' mode where bots don't get any information through eyes or reference variables.  You'd have to 'feel' your way around.  Talk about unreal speed.

[Old Henk]

One of my bots is visually impaired. Well, actually I made it to be. Hmmm, I think I hear  DB-activists knocking at my door...

[Zelos]

im giving up on you guys, its simply to hard for you to understand that a momentum to the right is minus for one that are to the right. like the borgs in star trek says "you think so 3 dimensianal"

[PurpleYouko]

im giving up on you guys, its simply to hard for you to understand that a momentum to the right is minus for one that are to the right. like the borgs in star trek says "you think so 3 dimensianal"

It doesn't apply to DarwinBots though.

The medium in which they swim is fictional. It isn't actually there so we can't transfer momentum to millions of non-existent atoms of water, air, chicken soup or whatever the hell you want to imagine the bots swimming through.

When a robot slows down due to friction, where does its momentum go?
When a robot speeds up with a .up command where does its momentum come from?
Without modeling every atom of the medium in which they live, complete with eddy currents, viscosity and all the other fun little things that exist in the real world, there is no way to fully conserve momentum in DarwinBots.

And even if we could, who the heck cares?

Anyway how could a DarwinBot think in 3 dimensions when they are clearly 2 dimensional creatures.

[Zelos]

I dont say we shall simulate all of them, it just went from fictionalmomentum to real momentum, or atleast I thought so. of course we cant simulate all of them, but if 2 bots bump into each other I think it shall follow that rule, but still what ive seen, you guys truly are "3 dimensianal" in ur thoughts

[shvarz]

Zelos, when you have free time, try the following: Find an experimental subject, then run towards him/her as fast as you can and bump into him (or her).  Measure the outcome and see if it matches the expected "momentum conservation".  Try it with subjects of different sizes  Try doing the same in water   :)