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Custom Chipmunk class/object

(18 posts) (4 voices)

Started 1 year ago by mrTortex
Latest reply from mrTortex

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mrTortex
Member

Hello.

I'm not sure where to ask this. Classes in Obj-C are really messing with my head. I have made some simple classes which place balls on the screen, you pass through a radius, location etc. So I have basic classes working.

However, I'm stumbling now. I want to take all the code for my Chipmunk/Spacemanager player and sub class it all. I cannot figure out things like placing my chipmunk body/cpCCSprite into my Spacemanager shape, which is declared in the main classes init method. If I try to pass it through as a string, that compiles but doesn't work.

So, does anyone have a basic example of say a simple ball class which uses Chipmunk? Or, as I'm happy to read can anyone suggest a good place to learn about making my own methods in Obj-C? I've read the primer, I've gone through the relevant bits in Cocoa Programming for OSX and watched some videos on Youtube, but no joy. Basic classes are fine, but anything slightly more complex and it all goes horribly wrong.

They say the best way to learn is to start a project with many problems, and work through them one at a time. I agree, I've learned so much from making my little game. Thank you to all the people who've helped so far. Almost there. :)

Posted 1 year ago #

mrTortex
Member

Hello.

Following some help from assorted forum members, this is now almost working. My header:

@interface trainerBody : cpCCSprite {
}
//+(id)tBody: spaceManager:(SpaceManager*)smgr;
-(id)initTBody:(int)flag spaceManager:(SpaceManager*)smgr;

and main file:

-(id)initTBody:(int)flag spaceManager:(SpaceManager*)smgr {
	//self = [super initWithFile:@"Ball.png"];
	if(self != nil) {
		self = [super initWithFile:@"Ball.png"];
		cpBody *body = cpBodyNew(250.0f, INFINITY);
		cpShape *shape = cpCircleShapeNew(body, 30.0f, cpvzero);  //last bit is the offset
		CPCCNODE_MEM_VARS_INIT(shape)
		shape->e = 0.8;
		shape->u = 0.7;
		shape->collision_type = 2;
		[smgr addShape:shape];
	} return self;
}

this gets added to my level in the main file with:

trainerBody *tb = [[trainerBody alloc] initTBody:4 spaceManager:smgr];
		tb.position = cpv(200, 200);
		[self addChild:tb];

What I'd like to do now is in the class, is to have more than one shape/body/sprite be created, and add them all as a bundle attached with various joints. I have the code for the jointed final model if it would help to post that? From what I can see, I can only add one cpCCSprite per class, am I correct?

Posted 1 year ago #

mobilebros
Moderator
Can I ask you what you're hoping to accomplish by creating one node made up of multiple shapes and joints? I have done something similar where I use a CCLayer that contains all the "parts" like shapes a joints, just so they're in one place and I can easily access them.

Also I noticed you put that (int)flag part in from my other example, lol; you can just scratch that part, since you don't use flag anywhere:
```
-(id)initTBody:(SpaceManager*)smgr
```
and then call it:
```
trainerBody *tb = [[[trainerBody alloc] initTBody:smgr] autorelease];
```
I added the autorelease because it's good practice, the addChild statement below will actually retain it for you, so if you don't release it on your end, it'll be a memory leak. (this is because alloc does a retain for you)
Posted 1 year ago #
mrTortex
Member

Hello.

I uses the flag to set my group number to control self collisions, I just didn't bother to rename it. :) Quite like the name.

My player character, and the enemies, are built of lots of bodies which are held together with all sorts of pivots and constraints. Some are quite complex, and so instead of copying/pasting the code into each Level class I thought I'd make a Player class and build them in there. So I'd ideally like to be able to say, in my Level code; create this player group of bodies and cpCCSprites and stick it here, added to this space - instead of create this body, create this body, create this constrant etc etc. 3 lines instead of 150.

It doesn't have to be one node, it can be as many as it takes. I just want to have it all in a class. I think I'm explaining it poorly.

Basically, it's like a button class but made of many cpCCSprites and bodies etc.

Posted 1 year ago #
mobilebros
Moderator

I see what you're saying, I suppose I would lean towards making the player it's own CCLayer or even just a CCNode who's position is always zero.... the reason I say this is because Chipmunk has no concept of Parent-Child relationships, so coordinates must match "world" coordinates or you're going to get funky results. As for cpCCSprites, they are definitely designed to hold just one shape.... hopefully that all helps a bit.

Posted 1 year ago #
hm50
Member

Should this line:
@interface trainerBody : cpCCSprite {

be more along the lines of :
@interface trainerBody : cpCCNode {
or
@interface trainerBody : CCNode {

just wondering, it seems to me that the object created would always be a cpCCSprite and not a cpBody, which would make it hard to access.

Posted 1 year ago #

mrTortex
Member

Hello.

This is how it is now, on the edge of working..

Header:

@interface trainerBody : cpCCNode {
}
-(id)initTBody:(int)flag spaceManager:(SpaceManager*)smgr activeLayer:(CCLayer*)myLayer;
@end

Main:

@implementation trainerBody

-(id)initTBody:(int)flag spaceManager:(SpaceManager*)smgr activeLayer:(CCLayer *)myLayer {
	if(self != nil) {
		cpBody *_body = cpBodyNew(250.0f, INFINITY);
		cpShape *_shape = cpCircleShapeNew(_body, 30.0f, cpvzero);
		CPCCNODE_MEM_VARS_INIT(_shape)
		cpCCSprite *_sprite = [cpCCSprite spriteWithShape:_shape file:@"Ball.png"];
		[smgr addShape:_shape];
		[myLayer addChild:_sprite];
	} return self;
}

Implementation:

trainerBody *tb = [[trainerBody alloc] initTBody:3 spaceManager:smgr activeLayer:gameLayer];
		tb.position = cpv(200, 200);

Now, this works perfectly. But it's a single object, and I'm trying to build a cluster of objects in my class so I change the main to:

@implementation trainerBody

-(id)initTBody:(int)flag spaceManager:(SpaceManager*)smgr activeLayer:(CCLayer *)myLayer {
	if(self != nil) {
		cpBody *_body = cpBodyNew(250.0f, INFINITY);
		cpShape *_shape = cpCircleShapeNew(_body, 30.0f, cpvzero);
		CPCCNODE_MEM_VARS_INIT(_shape)
		cpCCSprite *_sprite = [cpCCSprite spriteWithShape:_shape file:@"Ball.png"];
		[smgr addShape:_shape];
		[myLayer addChild:_sprite];

		cpBody *_body2 = cpBodyNew(250.0f, INFINITY);
		cpShape *_shape2 = cpCircleShapeNew(_body2, 30.0f, cpv(50, 0));
		CPCCNODE_MEM_VARS_INIT(_shape2)
		cpCCSprite *_sprite2 = [cpCCSprite spriteWithShape:_shape file:@"Ball.png"];
		[smgr addShape:_shape2];
		[myLayer addChild:_sprite2];

	} return self;
}

At this point, it runs but all the objects appear at 0,0. Any ideas?

Posted 1 year ago #

mobilebros
Moderator

Well...... I would say that you don't want to derive from cpCCNode or cpCCSprite, you just want to derive from CCNode, you just want the class to be be a container for your cpCCWhatever's; therefore you will not call CPCCNODE_MEM_VARS_INIT anymore... and thats ok. I would also get rid of activeLayer, because you can just add trainerBody to the "active layer", just make sure trainerBody is always at 0,0. So something like:

@interface trainerBody : CCNode {
}
-(id)initTBody:(int)flag spaceManager:(SpaceManager*)smgr;
@end

/////////////////////////
@implementation trainerBody

-(id)initTBody:(int)flag spaceManager:(SpaceManager*)smgr
{
       [super init];  //this line is important too

	if(self != nil) {
		cpBody *_body = cpBodyNew(250.0f, INFINITY);
		cpShape *_shape = cpCircleShapeNew(_body, 30.0f, cpvzero);
		cpCCSprite *_sprite = [cpCCSprite spriteWithShape:_shape file:@"Ball.png"];
		[smgr addShape:_shape];
		[self addChild:_sprite];

		cpBody *_body2 = cpBodyNew(250.0f, INFINITY);
		cpShape *_shape2 = cpCircleShapeNew(_body2, 30.0f, cpv(50, 0));
		cpCCSprite *_sprite2 = [cpCCSprite spriteWithShape:_shape file:@"Ball.png"];
		[smgr addShape:_shape2];
		[self addChild:_sprite2];

	} return self;
}

By the way, the ININITY's on the bodies means that the shape will never rotate... fyi.

Posted 1 year ago #

mrTortex
Member

I am in love with you. ;)

How many weeks of pain? That's yet another pint I owe you. :)

Posted 1 year ago #
mrTortex
Member

Ah, spoke too soon. :) Both shapes appear at the same place and only one gets added to smgr. I've offset the positions of the shapes so tey should start 100 pixels apart, but no joy. Hmm.

EDIT: They both get added to the smgr space. Ignore that bit.

EDIT2: Ignore me again, I figured it out. :)

EDIT3: Hmm, they fall but don't collide wit the standard smgr screen bounds.

Posted 1 year ago #
mrTortex
Member

Nah, I spoke too soon. Both shapes get added, they enter at the same point. Offset makes no difference. I move the shapes manually, still no difference. I move the body, the shape, the cpCCSprite, still no difference! One shape will fall, the other gets stuck in mid air and rotates very slowly by itself. :) It's like Poltergeist. ;)

Also, they don't collide with each other or the smgr bounds.

Posted 1 year ago #
Mark Sawicki
Member

.. self deleted..

posting before thinking is bad.
I'm wrong.

-

Posted 1 year ago #
mobilebros
Moderator
hmmm try changing the last parameter in the next line to cpvzero:
```
cpShape *_shape2 = cpCircleShapeNew(_body2, 30.0f, cpv(50, 0));
```
because that's center of gravity related.... also try setting the positions after this directly:
```
_body->p = cpv(10, 10);
_body2->p = cpv(100, 100);
```
Posted 1 year ago #
mrTortex
Member

Yeah, already tried that. It's behaving really strange. I'm hunting for typos.

Posted 1 year ago #
mrTortex
Member

OK, I have the position worked out, can't say what it is because I don't know :) A typo probably, re-wrote the class and it's ok. But, I still get one shapes falling and the other just floats. Also, the one that falls collides with an invisible shape and the shapes do not appear at 10, 10 and 100, 100 - more like three times that value.

Posted 1 year ago #
mrTortex
Member
OK, this is interesting. If when I implement the class like this:
```
trainerBody *tb = [[trainerBody alloc] initTBody:4 spaceManager:smgr];
		tb.position = cpv(200, 200);
		[gameLayer addChild:tb];
```
They appear at the positions given in the class, offset the distance shown above. So 10, 10 in the class and 200, 200 moves the body to 210, 210. Simple enough, and useful as I can position the shapes in the class relative to each other, then position the entire thing where it needs to go. However, this also offsets the smgr space by 200, 200 so that 'invisible' thing was the smgr screen bounds. :) Why would they be offset along with my objects? I can share a link to the project if that helps?

Although this is frustrating, it's quite fun. This is the kind of problem perfect for a London meet up, social gathering to fix my mess. :)
Posted 1 year ago #
mobilebros
Moderator

Yeah, its what I was trying to say before, chipmunk has no knowledge of such a parent-child relationship... so setting a parents position to anything but 0,0 is going to shift everything (well everything chipmunk cares about).

[I tried implementing such a relationship in spacemanager, but it's just a performance bane and figuring out the rotation transform stuff is a bit tricky...]

Yeah you can either share the link or send it to support@mobile-bros.com; I tend to look at projects using SpaceManager and try to help.

Posted 1 year ago #
mrTortex
Member

Ahh, that's a bugger. :) That means none of this will work then I guess? Back to putting everything in the main body?

I wonder if Box2D suffers from this issue also?

Posted 1 year ago #

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