A fast, easy to use, free, and community supported 2D game engine
Well, long story short.
I am working on a portion of my game where the background is animating as if it is moving, but it really isn't. I am wondering what is the best way to send about 30 of the same sprites down the screen towards the player at different times from (seemingly) nowhere or off the screen?
Lol, I know there has to be a better way than creating 30 of the same sprites off screen and moving them towards the player :c)
robodude666
Member
If you're looking for a parallaxing effect where the upper most layer images moves faster than the very back layer then checkout the CCParallaxNode.
Otherwise, if you're creating objects or enemies that appear off screen on the left/right and run across the screen then simply create a CCSprite and apply a CCMoveTo action to them.
Thanks so much for your reply robodue.
Sigh. So the best way to do it is to create 30 CCSprites and then just have them run down the screen?
Darnit, I thought there would be a better, more efficient way. But this is fine to do :c) Thanks Robo!
Any other suggestions please holler dears.
Codemattic
Moderator
you could put them all in the same parent node. Then, each tick, iterate through that parent node moving all its children down by a certain amount.
Or - if they all are supposed to move together at the same speed, you could move the parent node and the children will move too.
robodude666
Member
Create an NSMutableArray and add each sprite to it. Later on use fast enum to go through all of the elements in the array and update the position:
In your class' interface:
NSMutableArray *mySprites;
In your CCLayer's init:
mySprites = [[NSMutableArray alloc] init];
for(int i = 0; i < 30; i++)
{
CCSprite *sprite = [CCSprite spriteWithFile:@"CoolSprite.png"];
[self addChild:sprite];
float farawayX = // ... ;
float someY = // ... ;
[sprite setPosition:ccp(farawayX, someY)]
[mySprites addObject:sprite];
}In your update routine:
for(CCSprite *sprite in mySprites)
{
CGPoint newPos = // ... ;
[sprite setPosition:newPos];
}I don't believe that CCSprites have a userData like Box2D b2Body objects do. You might need to create your own class that either is composed of a CCSprite or is a child of CCSprite and give them some member variables that describe their velocity, etc. This way you can make each sprite move at a different rate across the screen.
Take note that if you later decide to remove a particular CCSprite from the world make sure to remove it from the NSMutableArray with [mySprites removeObjectIdenticalTo:sprite]; or else you'll get bad access errors and crash!
@robodude, no sense in making an array to add them in.. just create a CCLayer:
in the .h
CCLayer sprites;in the .m
sprites = [CCLayer node];and update the code:
for(int i = 0; i < 30; i++)
{
CCSprite *sprite = [CCSprite spriteWithFile:@"CoolSprite.png"];
[sprites addChild:sprite];
float farawayX = // ... ;
float someY = // ... ;
[sprite setPosition:ccp(farawayX, someY)]
}for(CCSprite *sprite in sprites.children)
{
CGPoint newPos = // ... ;
[sprite setPosition:newPos];
}All nodes have an array of children: node.children
Its way nicer than to have to make an array
robodude666
Member
That also works, but I was just giving an example :).
As I said in my example, because he wants the sprites to move at different velocities it would be a good idea to create a custom class which contains a velocity at which the sprite will be moving at. It's also a good idea as one can store more information regarding that entity in the world and create some fancy functions to manage it.
If he decides to use inheritance then he can get away with creating a CCLayer/CCNode and add these 30 as a child... which is perfectly fine. Though, Objective-C is best used with composition, so you're better off keeping an array of the objects and looping through them.
I wrote the example based on what I would do. I've written an Actor super class that contains a b2Body and a CCSprite. I create children of this class for specific actors, and I store them in an array. Then I loop through them every tick and update their position. I personally find this much easier as each entity in the world contains specific data about itself. Seeing as Objective-C, and Cocos2D is leaning towards using a MVC design pattern the model owns the data and never the view (CCSprite). It also allows me to give the Actor's children special abilities and methods.
-robodude666
Steve Oldmeadow
Administrator
^Techy didn't give you valid code. I think the //...; is meant to imply you fill that bit in.
In your code above you are not assigning anything to newPos. What did you think //...; was? The magical mind reading operator? That would be cool.
Steve Oldmeadow
Administrator
Try
CGPoint newPos = CGPointMake(34,95);or
CGPoint newPos = ccp(34,95);You must log in to post.