2D rigid body physics engine

[hrsitcom]

i'm new at this... but i try to figure out certain formulars for it, (already got spheare collisions to work using this pytaghorean formular and distance checking etc), would you mind giving me the formular / way you u did use for making the program being able to detect the local x and y coordinate for each polygon? I'd be sooooooo glad :)

have a nice day

hrsitcom

[meming4]

what collision detection algorithm did you use? SAT? is this like if(ob 1 collides with ob 2) ob2 start moving in direction of ob 1 or something like that?

[Draknek]

@meming4 Yes, the collision detection uses SAT. The collision resolution uses the normal from SAT as the direction in which to change the object's velocities.

My later videos have rotating bodies which makes the collision resolution more complicated but the collision detection is still SAT.

[meming4]

@Draknek can you Give me a little sample code? maby just a formula? thnx

[Draknek]

@meming4 For objects without rotation, look up "particle physics".

[JamAndToe]

Actually, this isn't an engine. Just an application.

[PencilWorld]

not much like 'phun'

[cyborgtroy]

Wow, I'm 2nd year CS and we're studying databases :(

Also good to see you're using Ubuntu. Apparently.

[Draknek]

If you want to do something really interesting, you may have do it yourself in your own time.

That said, I don't know what your course is like but this was for my third year project, which was basically allowed to be anything we wanted.

[crazyfuturamafreak]

You are wasting your time. Chipmunk is open-source and better.

[eFFeeMMe]

Maybe he means to study physics engines, and not to produce a library for others to use. Just maybe. Still, Chipmunk's awesome!

[crazyfuturamafreak]

Let me rephrase:

Why to make a physics library for other's use, when there already exists a better one?

[eFFeeMMe]

Probably he hasn't read much from Dijkstra.

[danielt113]

just add some constraints and make each particle bounce separately

using verlet integration is probably the best way if your gonna use constraints

[jcgurango]

3rd year? and your still doing this? do something better dood..

[danielt113]

add rotations to that dude

[3Dinvent]

This really isn't that great...Its just a bunch of objects with precise collisions bouncing around....I could probably make better physics in open gml.

[THkaas]

You stupid, it's great!

[towardsnormal]

This is so cool! I wish I could program!

Question: Are the objects programmed to lose a little bit of energy when they hit each other, or are the collisions perfectly elastic? (I see as time goes on the objects move less... just wondering if that was only due to the fact that you were adding more mass to the system and hence lowering the average velocity of the objects).

[Draknek]

Hey, thanks for the interest.

I think the objects here bounce away from a collision at about 75% of their previous velocities.

This is why they settle on the floor; if they didn't ever lose any energy, they'd keep bouncing around forever (although as you note, their individual speeds might be quite low).

[eFFeeMMe]

I see Ubuntu... ;)

What software do you use for screen capturing? I use XVidCap, I find it to be very neat.

The engine is fantastic by the way! You should keep a version without rotation, I think it would be very useful in platform games, for instance.

[Draknek]

I use gtk-recordMyDesktop for video capture; it seems to work pretty well.

Thanks for commenting. Eventually I'll add the ability to enable/disable rotation per-body, but for the demos I've made so far, it hasn't really been necessary.

[BlueN0vember]

Impressive. Finally a use for M2 mechanics huh? =)

Once you add the rotation will you be done?

[Draknek]

There's still plenty to add after that: friction, compound bodies, springs, joints. And there's lots of optimisations to be made.

But all of a sudden it looks like I might be capable of doing this, so I'm happy.

[BlueN0vember]

Awesomeness. Well gl with that. Looks quite fun as it is, heh.

I use a similar methodology in my project; mass code generation slogs until it works, then interate through it making it work in a reasonable time frame xD.

You going to have ragdolls?

[Draknek]

Hmm, I guess it might be possible to make a ragdoll in it when I add joints.

It's not one of my targets, though.

[utdiscant]

Sorry, my last comment was kinda rude. What is your primary target?

[utdiscant]

Well i am in high school and i implemented an engine using verlet integration, it looks a lot cooler.

[yesimahuman]

And you must not have any friends, with that special attitude of yours.