[CCBox2D] I made a cocos2d-flavored wrapper for Box2D

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[CCBox2D] I made a cocos2d-flavored wrapper for Box2D

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Started 1 year ago by axcho
Latest reply from gargantuan

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axcho
Member

I made a cocos2d-flavored wrapper for Box2D. It's called CCBox2D.*

In other words, actual integrated Box2D support for cocos2d, for the first time ever. Yay, easy physics! :D

It's essentially the equivalent of Space Manager, except for Box2D instead of Chipmunk. But I am not familiar with Chipmunk, or Space Manager, so I can't comment on the similarities or differences.

You can get the code here:
https://github.com/axcho/CCBox2D

CCBodySprite wraps b2Body in a CCSprite.
CCMotorSprite wraps b2RevoluteJoint in a CCSprite.
CCSpringSprite wraps b2DistanceJoint in a CCSprite.
CCWorldLayer wraps b2World in a CCLayer.

Pretty simple.

There's a project template for Xcode 3, and an as-yet untested project template for Xcode 4. If you have Xcode 4, please test it out and let me know if it works!

Thanks, and good luck. :)

Let me know if you have any questions or suggestions!

* (It used to be called CCox2D, but fortunately I was persuaded to change the name. :p)

Posted 1 year ago #
andrew
Member

one suggestion I have would be to make a b2SpriteNode, similar to spacemanager's cpSpriteNode. This way you can implement things like setColor: with the rgba protocol.

Im at a hotel on my phone right now. but I've managed to add a method that allows you to add concave polygons. I'll post it here when I can.

Posted 1 year ago #
axcho
Member

Thanks for the suggestion. It's good to have some perspective from SpaceManager. That said, I don't understand what you're suggesting. :p

There is no cpSpriteNode in SpaceManager, as far as I can tell. There is a cpShapeNode, however. Is that what you meant?

There is also no CCSpriteNode in cocos2d, but there is a CCSpriteBatchNode.

I see that cpShapeNode has a "color" property. But so does CCSprite, and by extension (or inheritance, rather) so does my own CCBodySprite. Or am I just missing something? :/

That's awesome that you've added support for concave polygons! I appreciate you taking the time to be the first one to try it out. :)

Looking forward to seeing your code.

Posted 1 year ago #
jordo
Member

i like the new name better :P

Posted 1 year ago #
andrew
Member
sorry - I wasnt able to check the name, I meant cpShapeNode. I tried using the setColor: from CCBodySprite, but it didn't work as I had expected. What it does in SpaceManager is it sets the color according to the shape created. (i.e. if I made a circle shape, I could make a cpShapeNode for it, set the color, and then add it to the scene)

and here's the concave polygon support. I added Triangulate.mm and Triangulate.h to so that the concave polygons are made into convex triangles.

Triangulate.h
http://pastebin.com/gz8KGXYJ

Triangulate.mm
http://pastebin.com/iGzgRePJ

as for adding the concave polygon, I made this method for CCBodySprite. I wasn't sure how to name it, since it would have to be multiple shapes. I dont have much (or any) experience with Box2D, so I'm not sure what would be appropriate here. For now, it will just add numbers at the end of it (e.g. myShapeName would have myShapeName0000, myShapeName0001, myShapeName0002, etc). Maybe you have a better idea of what to do for it. (of course you need to include "Triangulate.h" as well)
```
-(void) addConcavePolygonWithName:(NSString *)shapeName withVertices:(CCArray *)shapeVertices
{
	CCArray *convex = [Triangulate processPoints:shapeVertices];

	for(NSUInteger i = 0; i < [convex count]/3; i++)
	{
		CCArray *triangle = [CCArray arrayWithCapacity:3];
		[triangle addObject:[convex objectAtIndex:i*3+0]];
		[triangle addObject:[convex objectAtIndex:i*3+1]];
		[triangle addObject:[convex objectAtIndex:i*3+2]];
		[self addPolygonWithName:[NSString stringWithFormat:@"%04d", i] withVertices:triangle];
	}
}
```
Posted 1 year ago #
axcho
Member

I like the new name better too. ;)

Thanks for the code, andrew, awesome! I think I'll try building that functionality into CCBodySprite.mm directly, since I'm trying to keep the number of code files to a minimum for the sake of newb-friendliness (the most daunting thing about Box2D for me was the sheer number of different classes and files).

How would you like me to credit you? Is this your code? What name do you want me to use? :)

As far as setting color for specific shapes, I don't think that would make sense in this context, as shapes are purely collision-detection objects, unrelated to the visual side of things. In CCBox2D as in cocos2d, graphics should be done with images. If you need separate graphical objects, these should be separate CCSprites (or CCBodySprites). Does that match your understanding?

Update:
The Xcode 4 template is now confirmed to work correctly! Woo hoo! :D I installed Xcode 4 and tested it out. I can't believe it - no bugs on the first try! :)

Posted 1 year ago #
andrew
Member

It's not my code, i cant get the link right now but searcg for "efficient triangulation code" and you should find the original. Its on flipcode.com. Also, you might want to change the increment code and put the array count call in a separate variable. it isnt good to call it for each iteration.

Posted 1 year ago #
andrew
Member
sorry, I was on my (slow) phone again - what I meant was that you should use this instead for the method:
```
-(void) addConcavePolygonWithName:(NSString *)shapeName withVertices:(CCArray *)shapeVertices
{
	CCArray *convex = [Triangulate processPoints:shapeVertices];
	NSUInteger numTriangles = [convex count]/3;
	for(NSUInteger i = 0; i < numTriangles; i++)
	{
		CCArray *triangle = [CCArray arrayWithCapacity:3];
		[triangle addObject:[convex objectAtIndex:i*3+0]];
		[triangle addObject:[convex objectAtIndex:i*3+1]];
		[triangle addObject:[convex objectAtIndex:i*3+2]];
		[self addPolygonWithName:[NSString stringWithFormat:@"%04d", i] withVertices:triangle];
	}
}
```
this way it wont call [convex count] every iteration.

I got the original code at http://www.flipcode.com/archives/Efficient_Polygon_Triangulation.shtml , but I'm not sure who to credit. I guess you can put his name, but he says that it wasn't his code. I don't really care about getting any credit though.

He released the code at http://codesuppository.googlecode.com/svn-history/r28/trunk/app/VsoFont/FloatMath.inl (CTriangulator class) as well, and it has an MIT license, so I assume that it would be OK to use it. So you might as well credit John W. Ratcliff for it.
Posted 1 year ago #
axcho
Member

Thanks, I'll try it out.

I just updated CCBox2D on GitHub with some fixes to make the units consistent. Now it uses pixels instead of meters, grams instead of kilograms, and degrees instead of radians, in every calculation that passes through the wrapper.

Posted 1 year ago #
Andreas Loew
Member

I really like this project!
Just decided to make my PhysicsEditor compatible with it... so let's see what I can do tomorrow ;-)

Posted 1 year ago #
jsantos98
Member

Hello,

I was checking your implementation and there is something wrong with the rotation.
In the demo, try to send a box so it colides with the edge of another and make it rotate.

You'll see the rotation is exactly the opposite.
I've added the debug draw code (you should have a property in your code to enable/disable it) and it shows the problem.

I'm just starting to learn cocos and objectiveC, but the problem seems to be in the conversion between degrees and radians.

Regards
Joao

Posted 1 year ago #
axcho
Member

Hmm, the rotation probably needs to be negated, to convert between Box2D and cocos2d coordinates. I'll check it out, thanks. Sorry about the bug!

Posted 1 year ago #
axcho
Member

I just fixed the rotation bug, thanks jsantos98! :D

New update:
https://github.com/axcho/CCBox2D/commit/9e4262c91fe838be378d28e543020c6ceb5e0912

Posted 1 year ago #
Andreas Loew
Member

Hi,

I created a branch with http://www.physicseditor.de integration:
https://github.com/AndreasLoew/CCBox2D

1) PhysicsEditor decomposes concave shapes several convex shapes. I name them shapename-1 shapename-2... Perhaps we'll find a better solution in the future

2) PhysicsEditor allows setting collision masks, groups and categories on each polygon of an object. This is quite handy e.g. if you have an enemy you can separate his head, and e.g. a shield. So the shield reacts other to a hit than the head. You set the same parameters currently on all shapes when createBody is called.
I changed that so that it is set in the addShape routine together with the other fixture parameters.

3) Calling addShape with _body already set creates a memory leak since you don't free the b2FixtureData. That's fixed

4) Added debug drawing. You can now enable debug drawing in the CCWorldLayer.

5) Fixed rotation. Your sprites (don't know why) rotate into the wrong direction. They are perfect while dropping (100% polygon - shape overlap) but as soon as they collide they rotate into different directions. Shape goes left, sprite goes right. You can see this with debug drawing turned on

6) Added a complete example including box2d, cocos2d and everything to try things out

Ah - some changes seem to be included now ;-)

Sent a push request...

Posted 1 year ago #

andrew
Member

//
 //  HelloWorldLayer.mm
-//  ___PROJECTNAME___
+//  Untitled2
 //
-//  Created by ___FULLUSERNAME___ on ___DATE___.
-//  Copyright ___ORGANIZATIONNAME___ ___YEAR___. All rights reserved.
+//  Created by Alex on 4/7/11.
+//  Copyright __MyCompanyName__ 2011. All rights reserved.
 //

might want to fix that

Posted 1 year ago #

Andreas Loew
Member

Creating sprites is a piece of cake now:

Init shape cache

[[CCShapeCache sharedShapeCache] addShapesWithFile:@"shapedefs.plist"];

Create sprite:

CCBodySprite *sprite = [CCBodySprite spriteWithFile:@"spritename"];
sprite.world = self;
sprite.physicsType = kDynamic;
sprite.position = ccp(p.x, p.y);
[sprite addShapeFromCache:name];
[self addChild:sprite];

To enable debug drawing simply call one or more of these on the CCWorldLayer:

- (void) debugDrawShapes:(BOOL)draw;
- (void) debugDrawJoints:(BOOL)draw;
- (void) debugDrawAABB:(BOOL)draw;
- (void) debugDrawPair:(BOOL)draw;
- (void) debugDrawCenterOfMass:(BOOL)draw;

Posted 1 year ago #

axcho
Member

Oops! Thanks for the catch, andrew, just fixed the header. :p

And thanks for the PhysicsEditor integration, Andreas Loew - I'm looking forward to trying it out. :)

Did you see that I fixed the rotation error?

Update:
Also fixed the addShape memory leak!

Posted 1 year ago #
Andreas Loew
Member

@axcho: Well - Didn't check the forum here when I crated the branch. I fixed the bug nearly at the same time when you did...

Posted 1 year ago #

Andreas Loew
Member

@axcho: Seems you did not fix the complete memory bug. You also need to delete the inner shape

// if the shape exists
        if (oldShapeData->shape)
        {
            // delete the shape
            delete oldShapeData->shape;
        }
        delete oldShapaData;

Posted 1 year ago #

axcho
Member

Heh, thanks for the notice - just fixed it:
https://github.com/axcho/CCBox2D/commit/e5be576b7cbf3c9e323ca3196a71f3f99e637835

Posted 1 year ago #
damiano
Member

axcho, first of all great work.
However, it's not clear to me how this architecture will impact memory.
For example, you hold a reference to CCLayerWorld in your CCBodySprite (I'm looking at the Hello World template code, method addNewSpriteWithCoords):

sprite.world = self;

What happens when you add a series of different bodysprites, then call CCDirector replace scene to load a new scene. To me, it seems like the dealloc of your CCLayerWorld will never get called and will cause memory leaks. But I did not test this, Im just going through code and trying to get a grasp of your architecture and see how flexible/scalable it is.

Posted 1 year ago #
axcho
Member

Hmm, that is a good question, damiano.

I'm not actually familiar enough with cocos2d to answer that question off the top of my head - I'll have to test it out. I think it should work fine, but I may have overlooked something.

CCBox2D is actually a port of my Box2D integration from another framework entirely, and there may be some differences in how these deallocations are handled...

Thanks for bringing up the issue - I'll look into it soon. :)

Update:
I just tried using [[CCDirector sharedDirector] replaceScene:[HelloWorldLayer scene]] in my example program, and the dealloc method in CCWorldLayer is in fact called correctly. And so is the onExit cleanup method in CCBodySprite.

So I don't think there's a problem. Yay?

Posted 1 year ago #
damiano
Member

Awesome! Thank you for looking into this right away. I've been looking myself into wrapping Box2D into friendlier classes, but you already done some terrific work here so I might consider using CCBox2D instead of coming up with my own.

Posted 1 year ago #
damiano
Member

I have another question.
I'm wondering what the implication of moving the following:

// returns a CCScene that contains the HelloWorldLayer as the only child
+(CCScene *) scene;

Into its superclass CCWorldLayer:
// returns a CCScene that contains the CCWorldLayer as the only child
+(CCScene *) scene;

Is there a specific reason why you keep the static initializer into the HelloWorldScene (and so I imagine any additional scene in your game) instead of having it only once into the super class CCWorldLayer?

Please, forgive me if this is a stupid question but I'm just trying to figure out the architecture. Also, I'm relatively new to Objective-C/iOS and it's a learning process.

Posted 1 year ago #
jandujar
Member

uooooo this is awesone, perfetly for my next project!!, and integrated with physicseditor!!!

Posted 1 year ago #
Andreas Loew
Member

@jandujar - PhysicsEditor.de support is on my branch waiting to be integrated by axcho ...

Posted 1 year ago #
axcho
Member

To answer your question, damiano, the only reason that HelloWorldLayer is set up that way is because whoever made the original "cocos2d Box2D Application" template set it up that way. I just ported it over to CCBox2D. And from what I've read, it's not a good example of cocos2d game architecture, unfortunately.

HelloWorldLayer is not part of CCBox2D. It's just a quick and dirty example, until I come up with something better.

As far as wrapping Box2D into friendlier classes, I'd say try using CCBox2D a bit first, and see if it does what you need it to. If not, making your own wrapper classes is always a fun exercise. :) At least for some of us. :p

Andreas Loew, apologies for the slowness. I've been really busy lately (as always)!

It's not a straightforward merge for me, since I want to avoid exposing the Box2D classes entirely, and I have an idea for how to deal with setting collision groups for individual shapes that is more elegant and works with the collision callbacks I have already set up. Still have to try that out...

Posted 1 year ago #
VTX
Member

Thanks a lot for this awesome Wrapper!

Got a question: I want to remove a CCBodySprite when a collision callback happens.

It isn't currently clear to me how I would do that?

Posted 1 year ago #
damiano
Member

axcho, thank you so muc for being so kind in answering my beginner questions ;-)

I noticed another thing. In CCBodySprite, init, you allocated 2 mutable dictionaries, but I can;t find any release call for them when you dealloc the CCBodySprite:

_shapes = [[NSMutableDictionary alloc] init];
_shapeData = [[NSMutableDictionary alloc] init];

Wouldn't this cause a memory leak?

Posted 1 year ago #
juanpare
Member

This is great!
One thing, the templates are old, if I start a project from the template, the code not is the last.

Posted 1 year ago #

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