Looking for a Sprite Kit Game Engine? Check out Kobold Kit!

In case you missed the news: Sprite Kit is Apple’s 2D rendering engine for games, announced with iOS 7 at WWDC 2013 by merely mentioning it among other new APIs. A small step for Apple, a giant leap for gamedeveloperkind. This changes everything!

Many compare Sprite Kit with cocos2d-iphone. Don’t ask me why, they just do. 😉

If you’re a registered Apple developer you can check out the Sprite Kit Programming Guide and the SpriteKit.framework reference yourself.

Sprite Kit is under NDA, like the rest of iOS 7, so I won’t spell out any details here. I posted my list of strengths and weaknesses of Sprite Kit on the developer forum, where we can freely discuss such details.

Here let me just try to answer the questions: why did Apple create Sprite Kit, and why now?

The Biggie: Apple acknowledges games!

Apple finally understands the significance of games for their platforms! Sprite Kit is acknowledgement of that fact. Rejoice!

Especially if you consider the rumored Apple TV set: imagine a television set that runs iOS with an App Store to download and buy YOUR games. Interestingly, iOS 7 also adds an API for 3rd party game controllers, think of joypads, like those you get with an Xbox or Playstation.

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This Kobold2D FAQ article explains the difference between Corona SDK and iPhone Wax library, and evaluates the existing and future options for Lua scripting in Kobold2D.

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iTileMaps: TMX Tilemap Editor for iPad

On May 3, 2011, in tools, by Steffen Itterheim

iTileMaps developed by Vsevolod Klementjev is a Cocos2D app for iPad that allows you to edit tilemaps in the TMX format, the same format used by the popular Tiled Map Editor.

Although built with Cocos2D the tilemaps created with iTileMaps can be used with any game engine that supports loading the TMX format. To get ahold of the tilemaps created with iTileMaps you can export them directly to your game or send them via e-mail. Great for designing levels on the road!

Check out this fast-forward movie to see it in action:

Check out the iTileMaps website and/or get it on the iTunes App Store.

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While helping others solve their cocos2d project issues over the past year it became obvious that many projects have at least one major problem in one of these areas:

  • memory management
  • resource management
  • code structure

Examples

Memory management issues normally range from allocating too much memory, either by loading too many textures up front which are only going to be needed later, or by memory leaks such as scenes not deallocating when switching scenes. Resource management problems range from not adding the right resources to the right target, often resulting in increased App size because resources are added to the bundle but never used by the App. It could also mean loading identical resource files except that they have different filenames (copies?), using up additional memory. Or not tightly packing sprites into Texture Atlases but instead using one Texture Atlas per game object – while this is understandable from a standpoint of logical seperation it does waste opportunities for optimization.

Finally, code structure or lack thereof regularly leads to “everything in one class” code design which is most likely an evolutionary process rather than intentional. It’s not uncommon to see classes with thousands of lines of code, sometimes even going past 10,000 lines of code in one class. Other things are using too many CCLayers without them adding a clear benefit, for example just to group all nodes at a specific z order together or to group them by functionality, eg one layer for enemies, one for players, one for background, one for UI, one for score, one for particle effects, and so on – without any of these layers being used for what they’re really good at: modifying multiple nodes at once, like moving, scaling, rotating or z-reordering them. And of course there’s the copy & paste hell, large blocks of code reproduced in various places only to modify some parameters instead of creating a method which takes the modifiable parameters as arguments. Even professionals I worked with got so used to doing that it became hard just to overcome the resistance of letting go of old habits. But they learned.

Summary

Nothing of this code design and structuring strikes me as odd or surprising. I’ve written code like this myself. I also believe if it’s good enough and works, then why the hell not? It’s a matter of experience and it’s only with experience that you clearly see how to improve things. This boils down to the regular learning curve where only training and tutoring and just simply making mistakes and learning from them helps in the long run. That’s how we learn things.

On the other hand, the things like Memory and Resource Management can also be learned but they have a different nature. They can be statistically assessed, they could be calculated and verified automatically. This makes me wonder if there isn’t some kind of automation and information tools that would help developers achieve better results in terms of memory usage and resource management? In the meantime it’s all about raising awareness …

Raising Memory Awareness

Most importantly I think we need to raise more awareness to these issues to cocos2d developers. One step towards that would be for cocos2d to display a “available memory counter” alongside the FPS counter. I used to patch CCDirector to simply display memory instead of FPS since that was always more important to me. Fellow cocos2d developer Joseph sent me his version to display both – I simply didn’t think of the obvious. So if you’d like to see FPS and available memory next to each other I think you can handle the changes to CCDirector outlined here:

Raising awareness to leaking Scenes

In addition I highly, strongly and with utmost reinforcement (without pulling out a gun) recommend to cocos2d developers to frequently check your scene’s dealloc methods. Preferably add a breakpoint there, or at the very least add the logging line: CCLOG(@”dealloc: %@”, self). If you want a more visible but less intrusive method you could do something like flashing the screen or playing a sound whenever the last scene is deallocated, so that you get so used to it that when you’re not seeing or hearing it anymore it immediately raises your attention.

If at any time during the development of your project the dealloc method of a scene isn’t called when you change scenes, you’re leaking memory. Leaking the whole scene is a memory leak of the worst kind. You want to catch that early while you can still retrace your steps that might have caused the problem. Once you get to using hundreds of assets and thousands of lines of code and then realize the scene isn’t deallocated, you’ll be in for a fun ride trying to figure out where that’s coming from. In that case, removing nodes by uncommenting them until you can close in on the culprit is probably the best strategy, next to using Instruments (which I haven’t found too helpful in those cases).

I ran into such a problem once because I was passing the CCScene object to subclasses so that they have access to the scene’s methods. The subclass retained the scene and was itself derived from CCNode and added to the CCScene as child. The problem with that: during cleanup of the scene it correctly removed all child nodes but some of the child nodes still retained the scene. Because of that their dealloc method was never called, and in turn the scene was never deallocated.

cocos2d Book, Chapter 4: First Simple Game

On July 17, 2010, in Announcements, book, cocos2d, by Steffen Itterheim

Chapter 4 – First Simple Game

After Chapter 3 covered the fundamentals of the cocos2d game engine, this chapter will put to use what you’ve learned. The simple game is all about droping enemies that you have to avoid via accelerometer controls. Sort of like an inverse Doodle Jump. But it’s not just about the gameplay itself, I want the game to be reasonably complete with a main menu, scene transitions, game over and of course audio.

The chapter will be submitted on Friday, July 23rd.

Do you have any suggestions for the game?

What do you think should be in a first cocos2d game? Let me know!

Summary of working on Chapter 3 – Essentials

When I started the chapter I wasn’t really sure about its focus and progress was a little slow. Eventually it clicked and I found myself ending up having written more pages than needed and still having a great number of things left untold. The key was looking at the cocos2d API reference documentation and remembering what it was like when I was a beginner. Sure, every class, method and property is there but for a beginning cocos2d developer the API reference is just a huge list of names. In other words, if your experience was or is anything like mine was, it’s frustrating to work with the API reference.

I ended up writing about the cocos2d engine design and its scene graph first, the remaining 80% of the chapter explain in detail with lots of code samples how to use those darn CCNode classes. All the important ones are covered: CCNode, CCScene, CCLayer, CCSprite, CCLabel, CCMenu, CCMenuItem* as well as the Director, Transitions and Actions. Besides the code samples and how-to I’ve added numerous caveats, common mistakes, best practices and other nodes which are so very much needed to make any documentation complete.

For example, how Layers are best used for grouping other nodes together and of course how to enable touch and accelerometer input by adding the required functions which aren’t mentioned in the API reference since they are part of the iPhone SDK API. There’s also some weird recommendation floating around not to use too many Layers because they’re slow. I can’t find the source but what I did find was that this is only true if the Layers enable touch or accelerometer input, because that’s what costs a lot of performance. So what you don’t want to have is several layers accepting input, otherwise use as many Layers as you need – which shouldn’t be many anyway. And if you do need multiple Layers accepting input, why not just use one master Layer (possibly using a Targeted Touch handler) which forwards the input events appropriately to the other Layers?