Collision Help! :c) « cocos2d for iPhone

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Collision Help! :c)

(10 posts) (4 voices)

Started 1 year ago by mrmaiko
Latest reply from T.Hieu

Tags:

collision

mrmaiko
Member

Hey guys!

Thanks to Robodude and Techy! I was able figure out how to spew my random sprites using this method:

-(void) moveKale {

	int ranmX = rand() % 400;

	id animation = [CCMoveTo actionWithDuration:6 position: ccp(ranmX,-50)];	

	for(int i = 0; i < 1; i++)
	{
		int ranX = rand() % 450;

		int ranY = rand() % 420;

		if ( ranY > 300 ) {
		kale3 = [CCSprite spriteWithFile:@"Kale2.png"];
		kale3.position = ccp(ranX,ranY);
			[self addChild:kale3 z:30 tag:kTagKale];

			[kale3 runAction: animation];
		}

	}

};

I've ran into a little problem though. I tried adding the distance formula in the same method that creates the kale3 sprite,and I also tried writing a seperate one to check for collision:

-(void)collision {

	[self getChildByTag:kTagAndi];
	[self getChildByTag:kTagKale];

	float xDif = kale3.position.x - andi.position.x;
	float yDif = kale3.position.y - andi.position.y;

	float distance = sqrt(xDif * xDif + yDif * yDif);

	if (distance < 30) {

		[self unschedule:@selector(moveKale)];
}

But for some reason! It just isn't working! Sigh. IS it because my method is cycling every 1 second and it will only check for that one second on that sprite? Or do I just need to take a chill pill and re-think this thing?!

Posted 1 year ago #

pfg2009
Member
It's hard to say from this post what you are trying to do. Can you share a little more detail?

Also, there is a much more concise way to calculate distance between two points:

float distance = ccpLength(ccpSub(kale3.position, andi.position));

If speed is of concern (because you have 300 "kale"s running around), consider using distance squared. You avoid having to calculate the square root, which is an expensive operation:

float distanceSq = ccpLengthSq(ccpSub(kale3.position, andi.position)); if (distance < (30 * 30)) { ... }
Posted 1 year ago #

T.Hieu
Member

@mrmaiko:

[self getChildByTag:kTagAndi];
[self getChildByTag:kTagKale];

why don't you assign the sprites. It should be:

CCSprite andi = (CCSprite*)[self getChildByTag:kTagAndi];
CCSprite kale3 = (CCSprite*)[self getChildByTag:kTagKale];

@pfg2009: very useful info. Thank!

Posted 1 year ago #

mrmaiko
Member

@pfg2009 Thanks so much for your help and reply.

Well, I just want to check for collision on the kale that was drawn during that moveKale cycle. I will then add points through a label, in the future. I also want to remove that kale. moveKale cycles at interval:1.

Thank you T.Hieu! I will try that in the morning!

Posted 1 year ago #
Tim
Member

I'm curious as to why you're not considering using CGRect functions to determine if a point of a sprite is now within the field of another sprite?

Granted, it can get costly for many checks and it's not perfect for odd shapes, but I think it fits the bill for most scenarios.

@pfg2009 what do you rely for collision detection or are you using a physics engine?

Posted 1 year ago #
pfg2009
Member

@Tim: Every time I'm about to create my own collision engine, I think twice and decide to rely on a physics engine instead. Then, a month later, I realize that there are other extra goodies from the physics engine that come in extremely handy. I guess it depends on what you're doing. I just always find that throwing more physical simulation into the mix only helps and I don't have to reinvent the wheel.

Posted 1 year ago #
mrmaiko
Member

@Tim

I'm curious to learn how to do that. I'm not great with this, so I'm learning so much.

This simple collision is really all I have learned thus far, and has served me well in my other games. Um, any links to places that explain how to use your method Tim?

Thanks so much.

Posted 1 year ago #

mrmaiko
Member

Soo guys.

The problem I'm having now with my [simple] method of collision is if more than one Kale is created, the collision will only be picked up on the last kale that was added to the child. Even if other kales (there are usually only a maximum of two other kales) in the child. Again, I just need to detect when the andi sprite collides with the kale sprite so that I can add points, remove the collided kale, and update points. Here we go:

relative code in init:

andi = [CCSprite spriteWithFile:@"ball.png"];
[andi setPosition:ccp(240,120)];
[self addChild:andi z:1 tag:kTagAndi];

	[self schedule:@selector(moveKale) interval:1];
	[self schedule:@selector(collision) interval:0.1]; //played with interval

in moveKale:

-(void) moveKale {

	[self getChildByTag:kTagAndi];

	int ranmX = rand() % 400;

	id animation = [CCMoveTo actionWithDuration:6 position: ccp(ranmX,-50)];	

	for(int i = 0; i < 1; i++)
	{
		int ranX = rand() % 450;

		int ranY = rand() % 400;

		if ( ranY > 300 ) {
		kale3 = [CCSprite spriteWithFile:@"Kale2.png"];
		kale3.position = ccp(ranX,ranY);
			[self addChild:kale3 z:0 tag:kTagKale];

			[kale3 runAction: animation];

		}
					}
			};

in collision:

-(void)collision {

		[self getChildByTag:kTagAndi];
		[self getChildByTag:kTagKale];
		//[self getChildByTag:kTagBurger];
		//[self getChildByTag:kTagFries];

	//float fDistance = ccpLengthSQ(ccpSub(fries.position, andi.position));
		//float bDistance = ccpLengthSQ(ccpSub(cheeseburger.position, andi.position));

		float distanceSQ = ccpLengthSQ(ccpSub(kale3.position, andi.position));

		if (distanceSQ < (90 * 90) ) {
			[self getChildByTag:kTagKale];
			points++;
			[scoreLabel setString: [NSString stringWithFormat: @"SCORE: %d", points ]];
			[self removeChild:kale3 cleanup:NO];
		}

And thats pretty much it. I dont know how to draw CGRects and use those for collision yet. But if somebody could lead me in the right direction to keep all of my kales in check for collision, that would be amazing.

Posted 1 year ago #

mrmaiko
Member

*bump

Posted 1 year ago #
T.Hieu
Member
@mrmaiko: You can keep all of your kales in checking for collision by using the right tag.

1. When you init a kale, give it a tag when add it to the self. If you have three kales, the tags should be: kTagKale1,kTagKale2,kTagKale3 (These three tags should be in order so that it's easier to check for collision)
```
[self addChild:kale1 z:0 tag:kTagKale1];
[self addChild:kale2 z:0 tag:kTagKale2];
[self addChild:kale3 z:0 tag:kTagKale3];
```
2. When you check for collision, you run a loop to check for all kales (three in my example):
```
-(void)collision {
   int tempTag = kTagKale1;
   for (int i=0; i< 3;i++){
       CCSprite *tempKale = [self getChildByTag:tempTag];
       [Check collision code here ...];
       tempTag++;
   }
}
```
Hope this help.
Posted 1 year ago #

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