cocos2d for iPhone

A fast, easy to use, free, and community supported 2D game engine

1. 

   natanavra
   Member

   Hello,
   using chipmunk in my game, recently decided to create a class for my meteors, a Sprite class.
   Anyways I use chipmunk for physics setup and I was wondering if it's ok to update the object from inside the class, and remove it from inside the class as-well.
   I mean, I have an instance of my Meteor class inside my GameLayer, and I call updateShape on my space, but I can't get reference to my class (Meteor class).
   So... do I implement the update method inside my Meteor class and then call it on the object from the updateChipmunk method? like so:

   - (void)updateChipmunk:(ccTime) delta {
           for( Meteor *m in meteorArray)
                 [m update];
   }

   Or maybe there's a way to access the meteor instance from within the eachShape??
   Any advice on how to implement Sprite + chipmunk classes inside a game would be greatly appreciated, as I really think this is necessary - using the power of OOP I mean.

   Posted 2 years ago #
2. 

   natanavra
   Member

   Additionally, I tried removing the shapes and bodies from inside the object... having a
   remove:(cpSpace *)space method, but that won't work as it gets stuck inside a loop.
   I decided to release the shapes in the GameLayer, but I still want to know about best practices when talking about chipmunk inside object classes.

   Posted 2 years ago #
3. 

   natanavra
   Member

   update....
   If I try removing a shape that is inside the class I get an EXC_BAD_ACCESS, and it shows me the cpShapeDestroy method inside chipmunk... any ideas? if I remove the body but not the shape, I get an EXC_BAD_ACCESS as-well but refered to the cache method.

   Got no idea how to deal with this.

   Posted 2 years ago #
4. 

   pabloruiz55
   Member

   hi natan, from what you say i think the problem would be that you are removing the body or shape from the object, and as soon as the program goes into the part that loops through the objects to update the bodies, it enters that object and does not find the bodie/shape.

   I would try, removing the object from the array also, so it is not accessed in the loop. Or mark the object as removed and in the loop

   for( Meteor *m in meteorArray)
   {if(!m.removed)
   [m update];
   }

   Posted 2 years ago #
5. 

   natanavra
   Member

   Already did that pablo, I have a property BOOL isOutOfScreen and I make my calculations inside my update method and I put an if(isOutOfScreen) return; right at the start of the method.
   Hmm I tried a few things more, and it seems the sprite dealloc isn't getting called.
   I'll dig through the code later today to find the source.
   Will update!

   Posted 2 years ago #
6. 

   natanavra
   Member

   Finally found the source of the problem, I was double releasing the cpBody and cpShape. fixed!
   If anyone's interested in the class code, I'll post it here.

   Posted 2 years ago #
7. 

   Devnoob
   Member

   i am having problems in accessing space from a Sprite class.i got exc_bad_access

   the space is declared in my GameLayer class like this

   cpSpace* space;
   @implementation ....

   then in my sprite class
   ido

   extern cpSpace* space;

   Posted 2 years ago #
8. 

   yohann305
   Member

   I'm interested in the class code, i love reading code, just as an exercise, and we might learn a technique on the way.

   Posted 2 years ago #
9. 

   natanavra
   Member

   Wow, that's a dead thread lol...
   Anyways, here's some of the implementation (basic):

   //.h file
   @interface Meteor : Sprite {
   	cpShape *shape;
   	cpSpace *space;
   }
   @property cpShape *shape;
   
   - (void)setSpace:(cpSpace *)sp;
   - (void)remove;
   
   @end

   And here's the .m file:

   - (id)init {
       if(self = [super init]) {
           //mass and radius are my own variables, I use singeltons for Data Managment.
            cpBody *body = cpBodyNew(mass, INFINITY);
   		body->p = self.position;
   
   		shape = cpCircleShapeNew(body, radius , cpvzero);
   		shape->data = self;
   		shape->e = 0.8;
   		shape->u = 0.7;
   		shape->collision_type = 2;
       }
       return self;
   }
   
   - (void)setSpace:(cpSpace *)sp {
   	space = sp;
   	cpSpaceAddBody(space, shape->body);
   	cpSpaceAddShape(space, shape);
   }
   
   - (void)remove {
   	shape->body->p = ccp(350, 480 + radius + 10);
   }
   
   - (void)dealloc {
   	cpSpaceRemoveBody(space, shape->body);
   	cpSpaceRemoveShape(space, shape);
   	cpBodyFree(shape->body);
   	cpShapeFree(shape);
   	shape = nil;
   	space = nil;
   	[[TextureMgr sharedTextureMgr] removeAllTextures];
   	[super dealloc];
   }

   Not sure this is the best way to do it, but it works.
   I set the space, the moment I create the object (gives me pointer reference to main space in the GameLayer) and I use these classes with object managers.
   I'm sure you can figure it out, I mean how to add stuff to the class (e.g. BOOL usable).

   I hope this would help someone,
   ~ Natanavra.

   NOTE: Just thought about it, we could create a singleton for physics engine management... would make thing easier, wouldn't it?

   Posted 2 years ago #
10. 

    natanavra
    Member

    The prev post is way too long, so Devnoob probably won't see this one, so I'll double post (sorry).
    @Devnoob, you should declare your space in GameLayer as extern too (If I'm not mistaken), better yet - use my method described above.

    ~ Cheers! Natanavra.

    Posted 2 years ago #
11. 

    Devnoob
    Member

    ok thats realy good...

    the extern thin worked for me i dont know how but it dead after many builds i dont know whats was wrong it seams a problem with xcode and clean

    i think yhat your solution is better because u dont have to deal with c functions like makeBody();

    Posted 2 years ago #
12. 

    natanavra
    Member

    I hate c functions, 'cause they're non-object oriented, and I only learned obj-C, I'm a newbie to programming myself.
    So, writing the extern in gameLayer like so:

    //GameLayer.m
    extern cpSpace *space;

    or did it work like you had it?

    Posted 2 years ago #
13. 

    Devnoob
    Member

    yes extern worked add :
    //GameLayer.m
    cpSpace *space;

    and in sprite class
    extern cpSpace *space;

    and you can access space directly

    Posted 2 years ago #
14. 

    natanavra
    Member

    K, although I'm not gonna change my code, I like it! lol.
    ~ Natanavra.

    Posted 2 years ago #
15. 

    Devnoob
    Member

    :) thanks for your code...lol

    Posted 2 years ago #
16. 

    mobilebros
    Moderator

    Hey there all, I actually just made a post about an opensource project we've been working on called Chipmunk-SpaceManager; its an objective-c wrapper to chipmunk, but it also has a few classes for cocosnodes that implements a lot of nice "sync" functionality (but not the auto free you have up in the dealloc there... yet). Anyway if you're interested heres the project page:

    http://code.google.com/p/chipmunk-spacemanager/

    and heres the article page:

    http://www.mobile-bros.com/?p=409

    Posted 2 years ago #
17. 

    Codemattic
    Moderator

    excellent, an Objective C wrapper for Chipmunk. Very nice! In looking through the demo code I dont see anything that wouldnt work with cocos2d v8.x

    Posted 2 years ago #
18. 

    mobilebros
    Moderator

    Yes actually the example is using 0.8.1. I just got the first draft of the documentation checked in and also implemented an option for automatic freeing of the associated shape, so thank you natanavra for the great idea.

    Posted 2 years ago #
19. 

    PhilM
    Member

    @mobilebros: loving the wrapper. Just having a play with your example from the svn, and its shows a lot of nice features.

    I like the fact your using a newer version of chipmunk with the recent joint/constraint changes.

    Any tips for adding dragging of sprites to the example? I've commented out the '[ballSprite applyImpulse:ccpMult(forceVect, 3)];' line in touches began, and am trying to replace it with the code based on the 'click' method in the latest ChipmunkDemo (http://code.google.com/p/chipmunk-physics/source/browse/trunk/Demo/ChipmunkDemo.c#246)

    After adding in some extra declarations for 'cpConstraint *mouseJoint = NULL;', GRABABLE_MASK_BIT, and exposing the _space property, and accessing it via [smgr _space] everything compiles ok. But it crashes without error at 'cpSpaceAddConstraint([smgr _space], mouseJoint);'

    I know I'm not using the manager properly, by exposing the _space as a property, & perhaps thats the problem. I just wanted to see if it was possible, and as a chipmunk novice, that seemed like the easier route. Any ideas at all?

    Thanks.
    Phil.

    Posted 2 years ago #
20. 

    mobilebros
    Moderator

    From what you've said everything sounds fine, I'm assuming mouseJoint is not NULL when you call cpSpaceAddConstraint. I was thinking about making space a property and probably will since it would make sense. Not sure how it'd crash without error, but xcode is strange sometimes, maybe try breakpointing that line and seeing if you can come up with some more info.

    But you should be able to use SpaceManager's addpivot routine like this:

    cpConstraint *mouseJoint = [smgr addPivotToBody:toBody fromBody:fromBody worldAnchor:anchr];

    This should achieve the same effect from what I can see from that demo.

    Posted 2 years ago #
21. 

    natanavra
    Member

    I like your wrapper, I'm really glad I somewhat helped your project!
    ~ Natanavra.

    Posted 2 years ago #
22. 

    Codemattic
    Moderator

    @mobilebros, maybe instead of cpSprite it should be cpNode which is a subclass of CocosNode instead of Sprite. That way developers could put any kind of node in the simulation. So you create a cpNode and then add a Sprite as a child of that (or a Label, etc...) More flexible, not sure how much slower that would run, I dont think it would be noticeable.

    Posted 2 years ago #
23. 

    mobilebros
    Moderator

    @Codemattic, sorry the reply is so late but that is a very good idea :)

    Posted 2 years ago #
24. 

    michu
    Member

    hey, sorry to reactivate this old thread.

    any chance the space manager find a way to the trunk? as it really simplifies chipmunk development.

    cheers

    Posted 2 years ago #
25. 

    mobilebros
    Moderator

    @michu, I'm down for including it; but of course that decision is up to Riq.

    The next version of SpaceManager will be using chipmunk v5 and be compliant with cocos2d v0.9 so that'd be the version to shoot for if he decides yes.

    Posted 2 years ago #
26. 

    riq
    Key Master

    @mobilebros: There are many tips that are useful, but I prefer to have the cocos2d source code as "slim" as possible. But since there are many useful tips, the alternative would be have a page that the "Tips" page updated.

    Posted 2 years ago #
27. 

    sunsu
    Member

    Just looking at this for the first time. Man I wish this would have been around when I started! You get the object oriented benefits of Box2d with the simplicity of Chipmunk.

    Thanks for taking the time to do this mobilebros!

    Posted 2 years ago #
28. 

    mobilebros
    Moderator

    Haha thanks Sunsu, I'm pretty sure there were some posts with you chiming in that helped shaped the SpaceMananger, I remember you asking the same the questions about chipmunk when I was also learning about it.... so Thanks!

    Posted 2 years ago #

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