cocos2d for iPhone

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

1. 

   tatebn
   Member

   I've been playing around with cocos and chipmunk, and I got a demo working where I have a bunch of balls bouncing around the screen with the accelerometer.

   I'm trying to figure out how to make them rotate. Graphics programming is still new to me, so I'd love some help.

   Here's my update shape method. I need to get the shapes rotation and rotate the sprite with it.

   void updateShape(void* ptr, void* unused){
   	cpShape* shape = (cpShape*)ptr;
   
   	Sprite* sprite = shape->data;
   
   	if(sprite){
   		cpBody* body = shape->body;
   
   		[sprite setPosition:cpv(body->p.x, body->p.y)];
   	}
   }

   Thanks

   Posted 2 years ago #
2. 

   shivaz
   Member

   Google lots, and read lots :) It really helps. Go here: http://morethanmachine.com/macdev/?tag=cocos2d

   Then change your updateShape method to the following:

   static void
   eachShape(void *ptr, void* unused)
   {
   	cpShape *shape = (cpShape*) ptr;
   	Sprite *sprite = shape->data;
   	if( sprite ) {
   		cpBody *body = shape->body;
   		[sprite setPosition: cpv( body->p.x, body->p.y)];
   		[sprite setRotation: (float) CC_RADIANS_TO_DEGREES( -body->a )];
   	}
   }

   Posted 2 years ago #
3. 

   tatebn
   Member

   Very Nice. I got that working, had to add a cpMoment for the circle and a bit of friction. But it's on its way. Here's the issue now. The circles don't recognize the borders of other circles as a point of friction. So sometimes they just keep spinning, even if there are like 10 other circles touching them.

   Posted 2 years ago #
4. 

   tatebn
   Member

   jacked up the friction and it looks better, except when it's falling down the wall, then it's just ridiculous. but I think I can work with it. Thanks.

   Posted 2 years ago #
5. 

   mrgreen
   Member

   i had the same issue with rectangles that kept spinning and failing collissions at some point. in my case the solution was to use these values for my objects:

   mass: 200
   friction: 0.01
   elasticity: 0.8
   moment / intertia: 1000.0

   as the documentation is not really covering this, here is the code to set the moment for a rectangle which is done as a 4 vertex poly

   
cpBodySetMoment(body, cpMomentForPoly(1000.0, 4, verts, CGPointZero));


   Posted 1 year ago #

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