How to set collision type for game like crayon ball?

[ipmart]

Hi all,

Im a newbie in chipmunk and must say im very impressed with the physics engine, great work

Im having problem with a collision type.
I'm trying to detect a collision between balls with many different color, very similar to crayon ball
http://howlingmoonsoftware.com/iPhoneCrayonball.php

I set all balls to have collision type 1 and add cpSpaceAddCollisionHandler like this:
cpSpaceAddCollisionHandler(space, 1, 1, &collisionBegin, &collisionPreSolve, nil, &collisionSeparate, self);

But all balls doesnt collide with each other.

How do you set the collision type and cpSpaceAddCollisionHandler to achieve same thing like crayon ball?


Many thanks

[slembcke]

For Crayon Ball, each color of ball was a collision type (0-5) and we created collision handlers for each collision of a type to itself. It was as simple as a for loop for setting them up.

Code: Select all

for(int i=0; i<6; i++)
	cpSpaceAddCollisionHandler(_space, i, i, NULL, (cpCollisionPreSolveFunc)ballCollisionFunc, NULL, NULL, self);

[ipmart]

Thank you for replying,

I tried that but balls with same color doesnt collide with each other
only balls with different color will collide, the same color ball pass through each other.

How can i fix this?

Thanks in advance

[ipmart]

oh i found the problem, its because im returning 0 in the presolve function thats why the ball pass through
Silly me

oh ya another thing, would you mind to give me tips on how to detect 3 balls in same color touching each other?

Thanks in advance

[slembcke]

What you are looking for is how to find connected components of the graph. http://en.wikipedia.org/wiki/Connected_ ... ph_theory)

[ipmart]

Thank you for replying

Im trying to figure out the structure now.
Meanwhile im having problem accessing variable that passed as user data like this:

I set the handler this way
cpSpaceAddCollisionHandler(space, sheetCounter, sheetCounter, &collisionBegin, nil, nil, &collisionSeparate, self);
self is ccLayer

int collisionBegin(cpArbiter *arb, cpSpace *space, void *data)
{
CCLayer *myLayer = (CCLayer *)data;
int ballShapeArrayCount = [myLayer.ballShapeArray count]; <--- this one error: request for member 'ballShapeArray' in something not a structure or union

}

please let me know what error that i make


Many thanks

[slembcke]

That's a compiler error. First of all, are you sure the specific type is a CCLayer? By doing myLayer.ballShapeArray you are asking for the ballShapeArray property of CCLayer. If the property is defined on a subclass, you'll need to cast it to that class first. If you meant to get a field you need to use the '->' operator, and you also need to cast it to the correct class first.

[ipmart]

im passing self which is a CCLayer class into user data

I tried this
CCLayer *myLayer = (CCLayer *)data;
BallShape *myArray = (BallShape *)myLayer.ballShapeArray;
it come out with this error: request for member 'ballShapeArray' in something not a structure or union

if i change to this
CCLayer *myLayer = (CCLayer *)data;
BallShape *myArray = (BallShape *)myLayer->ballShapeArray;
this error: 'struct CCLayer' has no member named 'ballShapeArray'

please give me example of how do you access data variable if you pass in ssLayer into the user data field

Many thanks

[ipmart]

Here is the header of ballshape.h

#include <stdlib.h>
#import <Foundation/Foundation.h>
#import "chipmunk.h"
#import "cpShape.h"

@interface BallShape : NSObject {

cpShape *shapePointer;

}

@property (nonatomic) cpShape *shapePointer;

@end



and the implementation:
#import "BallShape.h"


@implementation BallShape

@synthesize shapePointer;

@end


I use this class to wrap cpshape pointer so i can add into nsmutablearray

[slembcke]

Looks like CCLayer is the Cocos2D layer class. Unless you changed the Cocos2D source, it is not going to have a field or property named ballShapesArray. What class was self? In order to call a property or use the -> operator, the compiler needs to know the precise class of the object you are calling it on. Neither can be used dynamically, it won't give you a warning like calling an unknown method, it's just a hard error.