2D Physics System

[kevglass]

I've ported and tidied some code from GDC 2006 for a 2D physics engine (all kudos to Erin Catto) - I decided I'll probably want a reliable 2D physics engine for future gaming projects. At the moment it only handles boxes but I'm hopefully going to extend it to include circles next and refactor the collision stuff along the way.

Webstart Demo Box Here

some screenshots:

http://www.cokeandcode.com/phys2d/screenshots/d1.png
http://www.cokeandcode.com/phys2d/screenshots/d2.png
http://www.cokeandcode.com/phys2d/screenshots/d3.png

Kev

[Evil-Devil]

Really cool. Good work

[Amos Wenger]

When will a Xith3D binding be available ? 

Games published by our own members! Check 'em out!

[kevglass]

Never really understoon binding a rendering layer to a physics layer in a formal manner - isn't that the job of the game engine?

Kev

[Amos Wenger]

Never really understoon binding a rendering layer to a physics layer in a formal manner - isn't that the job of the game engine?

Yes, you're absolutely right. Anyway that's why I stopped using ODEJava's Xith3D bindings and did my own linking : much clearer.

I was just kidding and wanting to know if you're planning to develop some more with Xith3D.

[kevglass]

Right now it seems my development system hardware is so rubbish it prohibits me from using Java3D, Xith or JME (all of which I've wanted to use just recently - hence the posts on the forums there). However, not being able to get basic terrain rendering at > 20 fps (due to my crap hardware, rather then the libraries in question) makes it less than endearing.

I think I'm going to be sticking to writing small extremely optimised games for now.

Kev

[rdcarvallo]

It works very well...
I also ported the code, but the demos of the stacks and the pyramid always exploded.
Did you use a bigger drag/friction to make the simulation more stable??

   Rafael.-

[kevglass]

Ah, if I knew someone else had already ported it - I would have just used that one

Re: Drag/Friction - no, it's just as it was before - though the demos arn't identical and I haven't tried a stack yet.

One thing I do notice is it seems the simulation isn't very reliable running at a step of anything other than 1/60.0f - I'll probably make this the default or something in this version.

Kev

[Amos Wenger]

Semi-offtopic :

I catched this sentence : "Ah, if I knew someone else had already ported it - I would have just used that one  "

That happens really often and.. well making a java.net project doesn't give so much visibility.

If some are interested, I am ready to make a site containing a repository of useful libs, for 3D (JOGL LWJGL Xith3D Java3D jME),
for physics (JOODE, your physic implementation, someone else which I can't remember the name unfortunately), for some other things..

The basic idea here is to share your libs to avoid some work for others.. Hmm maybe I'm not clear here anyway ask questions I'll answer

[rdcarvallo]

1/60 secs...
  That may be, I have it running at variable timestep.

1   2   3   4   5   6   7

//Pseudo-Java while(running){   dt = now -last;   update(dt);   render();   last = now; }

I will try  with fixed timestep.

   Rafael.-

Games published by our own members! Check 'em out!

[Amos Wenger]

Variable time-step is the nightmare of every physic programmer.

[Orangy Tang]

Variable time-step is the nightmare of every physic programmer.

And network programmer.

[Amos Wenger]

Variable time-step is the nightmare of every physic programmer.

And network programmer.

Sure.

[kevglass]

I will try  with fixed timestep.

   Rafael.-

Are you planning on releasing source and expanding the Box2D demo into a more general physics system? If so, should I stop and wait for your implementation?

Kev

[CommanderKeith]

WOW, that's not physics, its magic!!!!  Flawless from the look of the demos! 

At the moment it only handles boxes but I'm hopefully going to extend it to include circles next and refactor the collision stuff along the way.

I haven't read the slides & code yet, but I was wondering, can it do 2D polygons?  I've been hot on the trail for a way of doing physics for my 2D tank game.  I'd love to be able to use these methods you've both employed. 

Thanks,
Keith

EDIT: I read the code, but without knowing C I'm not comfortable with it.  From the slides it looks like doing the impulse method for polygons wouldn't be that hard so long as overlapping sections can be computed, which can be done.  If either of you would be so kind to share your java-ported versions I'd be happy to try to tweak it to work with 2D polygons.

[DzzD]

I love those demo. seems to works perfectly.

[nonnus29]

Yep, that's really amazing.  What's the status on the source code?  Will we get to see it?

 

[kevglass]

I was hoping to tidy the source code up a bit (add some documentation) before releasing. I was also going to try to refactor the collision code a bit to allow for circles before making it public.

If you're happy to take a look at the current state I could make it available sooner (maybe some repository somewhere).

However, I'd rather not step on anyone's toes - if rdcarvallo is already working on some open implementation I don't want to break that.

Kev

[kevglass]

I've added a stacking demo - seems stable even with slightly variable time steps (though I've now fixed it here to be 1/60.0f always).

Kev

[endolf]

Hi

vecmath jar is missing from the webstart dir so it all brokey now :/

Endolf

[CommanderKeith]

Not for me, it works sweet.  I love the stack with the shooting boxes... amazing.

[oNyx]

Hm. Put the +0.05f thing back in. Right now you get *massive* over/understeer effects if it ran flat (yield pretty much 0) for a while. (So, there was a reason that I put it there... haha... my bad )

And it also might knock out into the other direction as soon as yield hits Integer.MAX_VALUE. Heh. That might be a problem in 10 years

[kevglass]

There is no dependency on vecmath.jar any more - you've got a caching issue somewhere.

Kev

[rdcarvallo]

Kev,
  Your stacking boxes works great!  I looked into my code and It was
using fixed timesteps, so I have something wrong.
  Just continue coding. I did this only to play a little, and since it didn't  work
well, I didn't continue.

   Rafael.-

[kevglass]

Ok, the source is currently available here:

http://www.cokeandcode.com/phys2d/source/

And the demo is still at

http://www.cokeandcode.com/phys2d/phys2d.jnlp

It now shows contact points as the bodies collide - I think this will be useful for checking collision shape implementations.

I've just refactored out the collision routines so I can add circles next. Please bare in mind it's very much a work in progress and I'm still trying to get my head round the maths involved. I'm still developing so it might be tricky if anyone wants to start adding stuff right now - if theres any real interest I'll start some java.net or code.google.com (coogle?) projects to hold the source.

The source thats available right now is just a snap shot of what I'm working on - so there are still plenty of holes

Right now thought I'm just enjoying playing with the demo way too much.

Kev

PS. I've tried to stick 1.4 compatible for personal project reasons.

[kevglass]

Just added circles to the mix - seems the collision refactoring works ok. The demo has been updated with a few scenarions including circles rolling around.

I've been focusing on making it work rather than fast/light. There is work that needs to be done pulling the maths apart and making it optimal for speed and garbage. There's also some stuff that would be nice to do for detecting static bodies and ignoring them.

Kev

[shawnkendall]

Go show!

[oNyx]

Waaa neato!

[CommanderKeith]

& thanks for the source !  So when is a billiards game coming out!?

[Death33284]

Wow, this looks great kev   

Can we use this in our own games as long as we give you credit?