Kobold2D (Alpha) Demonstration

On June 26, 2011, in cocos2d, Kobold2D, by Steffen Itterheim

I recorded a screencast to give you a first impression of the current alpha version of Kobold2D. I’ll show you what is is, what it includes (so far) and how it improves the cocos2d development process.

Since recording the screencast I’ve added the Doodle Drop project from the book as an iOS game template project. I also added the Box2D & Chipmunk physics projects from the book and improved them to work on both iOS and Mac OS X.

Update

Here’s a screenshot showing the current list of template projects (Hello Kobold2D, Hello Cocos3D, Hello Cocos2D-X, Physics Box2D, Physics Chipmunk, Physics Chipmunk SpaceManager, Doodle Drop) and the Doodle Drop template running:

Updating Cocos2D in an Existing Project

On May 20, 2011, in cocos2d, support, Xcode, by Steffen Itterheim

Upgrading cocos2d-iphone is a recurring issue for many developers but since it happens so infrequently during the lifecycle of a project, there’s just no routine to follow. Eventually you might want to upgrade cocos2d-iphone, so the question arises: how do you do that with the least amount of trouble?

As I’m going through the process of updating over 70 (!) Xcode projects for the second revision of my Learn Cocos2D book, I thought I should outline the steps to upgrade an existing Xcode 3 project which uses cocos2d-iphone v0.99.x to a Xcode 4 project that uses cocos2d-iphone v1.0.x.

Prerequisites: software update

Obviously, you want to download the latest cocos2d-iphone version and unzip it to any directory. Just remember where you unzipped it because that’s where you’ll copy the new library folders from.

You also want to make sure you’ve upgraded to Xcode 4 by now, by installing the iOS 4.3 (or later) SDK, if you haven’t done so already.

Caution: Make sure Xcode is closed during the first steps.

Step #1: delete libs folder contents

In your project’s folder, in this case DoodleDrop03, select all folders in the libs folder and delete them without mercy:

You’ll end up with an empty libs folder. In other words, don’t delete the libs folder itself or in case you did, make sure you re-create the libs folder.

Caution: The reason why I delete all the libraries in the libs folder instead of simply overwriting the libraries with new ones is simple: you can expect the updated cocos2d-iphone version to have removed or renamed some files. By first deleting all libraries you can be sure that no “zombie files” exist which are no longer used but might still be compiled when you later re-add the libraries. Such zombie files would screw up the build process and generate errors like “Duplicate defined symbols” and other such mishaps.

Step #2: copy the library folders

The first thing you’ll notice when you want to upgrade the libs (Box2D, Chipmunk, cocos2d, CocosDenshion, cocoslive, FontLabel and TouchJSON) is that they’re in different folders in the cocos2d-iphone project that you’ve downloaded and unzipped.

Make sure you select the exact same folders that are selected in the screenshot below:

This difference in folder layout can be a bit confusing. What you need to be aware of is that the Box2D, Chipmunk, FontLabel and TouchJSON folders are in the external folder in the cocos2d-iphone project. Furthermore, the Box2D folder that you should copy is a subfolder of Box2d. Note the difference in capitalization of the letter D. You want to copy the folder with the uppercase D: Box2D. The same goes for the CocosDenshion folder, you should select the CocosDenshion folder inside the CocosDenshion folder.

Caution: Make sure you don’t select the Box2D Testbed folder – if you do and copy that as well, Xcode 4 might lock up building the project, consuming 100% CPU power and requiring a force quit to shut it down.

Note: If you use only Chipmunk or Box2D physics, or neither of them, you can skip copying these folders of course.

To complete the copy opertation, go to the libs folder and paste the copied library folders so that you end up with a libs folder that looks exactly like the image in Step #1.

Tip: If you prefer drag and drop you can just drag the selected folders from one Finder window to another onto your project’s libs folder. This may be easier to do but you should remember to hold down the Option key while dropping so that you actually copy the folders instead of moving them. The copy operation is indicated by the green + icon underneath the cursor as you drag & drop while holding the Option key.

Step #3: Remove Library References

Open your project in Xcode 4 now.

Select all groups under the cocos2d Sources group and hit Backspace to delete these groups (or right-click and choose Delete). You will be prompted with a dialog like in the screenshot below.

Make sure you select the default option Remove References Only to avoid deleting the new library folders you just copied:

Once you’ve removed the libraries groups, the cocos2d Sources group should be completely empty. You just got rid of all the old references, saving yourself from any potential compilation errors caused by references to files which may not exist anymore.

Step #4: Add Library Folders

Next you want to re-add your library folders. Select and right click the cocos2d Sources group and select Add Files to “NameOfYourProject”…:

Browse into the project’s libs folder and select all the library folders that you need in your project.

You may have noticed that my project doesn’t use any physics engine, so I decided to not add them here. If you do use Box2D in your project you would want to also select Box2D of course. Likewise if you use Chipmunk.

Note: While it’s not a problem to add both physics engine folders, doing so might increase your App’s size.

Now, here’s where you need to be careful with the options! You want to make sure they’re set exactly as in the screenshot below. Most importantly, when adding files Xcode will default to add the files to the project’s main target (in this case DoodleDrop) instead of the cocos2d libraries target.

Make sure that only the cocos2d libraries target is selected to avoid any build errors:

Step #5: Build it!

You should now try and build the project. If you’re lucky, there won’t be any errors and you can continue with your work.

But most likely, depending on your project’s complexity and the changes made to cocos2d-iphone, you may have to fix any build errors that occur. Most of them are likely to be caused by classes that have been renamed or functions that have been deprecated. In this case you’ll have to find out through the API Reference and release notes what the changes are and how to fix them.

Fixing the “missing base SDK” message

One common issue that occurs specifically to older projects is the “missing base SDK” error. I think it was the Xcode version introduced with Mac OS X Snow Leopard (released Aug. 28th 2010) that eventually fixed this dreaded issue by adding a “latest iOS” option for the Base SDK Build Setting.

If you see a message like this (especially if it gives you a compile warning or error):

You should change the Base SDK Build Setting of your project to use the “Latest iOS” setting:

Note: In some cases it may be necessary to close Xcode 4 and re-open it to make the “missing base SDK” message go away.

Correctly Inheriting Build Settings

Normally, all targets in Xcode inherit the Build Settings of the project by default.

However, once you’ve made any change to any Build Setting at the target level this Build Setting will no longer inherit changes made to the same Build Setting on the project level. The default reaction by many developers is often to bite the bullet and check and re-check the Build Settings of the project as well as all targets, and to make the same change as many times as you have targets in your project.

Don’t do that, there’s a better and easier way!

You can have a Build Setting at the target level to default back to inherit the Build Setting defined at the project level. Likewise a Build Setting at the project level can be set to inherit from the OS default setting. In the screenshot below I have purposefully changed the Build Setting at the target level:

To have it default back to the project setting, which is Latest iOS (iOS 4.3) all you need to do is to select that Build Setting and hit the Delete key:

Tip: Switching from the Combined to the Levels view when reviewing the Build Settings makes it easy to see which Build Settings are inherited and which aren’t. You’ll also notice that any Build Setting that has been changed at the current level and doesn’t inherit its value anymore is printed in bold letters.

That’s it!

Happy coding with your newly updated cocos2d-iphone project! This upgrade tutorial will also be printed in the second revision of the Learn Cocos2D book.

Tip: With Kobold2D it will be even easier to upgrade your project because a simple copy & paste of the files in the kobold2d folder will suffice. If there are ever any additional steps to follow we’ll describe them in detail of course.

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cocos2d Book, Chapter 5: Getting bigger and better

On July 23, 2010, in Announcements, book, by Steffen Itterheim

Chapter 5 – Getting bigger and better

The gist of this chapter will be to discuss the simple game project from the previous chapter. I threw everything into one class, clearly not what you want to do for bigger games. But getting from one-class to real code design is a big step which some hesitate to take. I’ll make that easier and discuss common issues and their solutions, such as what to seperate, what to subclass from and how you can have all the seperated objects communicate with each other and exchange information in various ways.

A big topic will of course be how to take advantage of cocos2d’s scene hierarchy and which pitfalls it may have when moving from a single-layer game to one which has multiple layers and even multiple scenes.

As for the chapter title I’m not so sure if that’ll be it. Maybe along the way while I’m writing I’ll change it. Suggestions welcome!

The chapter will be submitted on Friday, July 30th.

What’s your take on good cocos2d code structure?

Did you ever struggle with cocos2d design concepts? Or the cocos2d scene hierarchy? Or how to layout a scene and divide your game into logical parts? Tell me about it.

I know theses questions are somewhat generic to ask. It’s about the things that don’t feel right but there doesn’t seem to be a better, more obvious way. I think we all know some of those, if you do, be sure to tell me! Leave a comment or write me an email.

Summary of working on Chapter 4 – First simple game

The game I chose to make is called Doodle Drop and features dropping spiders and an accelerometer controlled alien trying to avoid the spiders. All in all it got divided into 8 concrete steps. Lots and lots of code comments, too.

It starts simple enough, adding resources to Xcode and adding sprites. It gets more gameplay-esque when the accelerometer-driven player controls got tweaked to provide acceleration and deceleration of the player object. In contrast, the spiders movements are driven only by actions.

I introduce you to two undocumented features of cocos2d, namely CCArray which is since v0.99.4 used to store all children of a node. The other are the CGPointExtension class which has all the functions normally provided by a physics engine, however not every game should link a physics engine just because one needs those math functions. That’s why CGPointExtension comes in handy.

With the ccpDistance method the collision checks are done. Simple radial collisions, and in debug mode the collision radii are drawn too.

In between the CCLabel for the score got replaced with a CCBitmapFontAtlas, because it killed the framerate. I shortly mentioned Hiero and how to use it in principle but for all the details there was no room. But while I was at it I created the Hiero Tutorial.

At the end of the project I added some polish which isn’t described in the book (too many details) but really adds to the game’s look and feel. The spiders drop, hang in there, then charge before dropping down, all done using actions. I’ve also added the thread they’re hanging from using ccDrawLine. And then there’s a game over label which shows even more action use.

One of the principles I followed is to stay away from fixed coordinates as much as possible. So the project, once finished, did run just fine on an iPad. Although the experience is a different one, there’s more spiders dropping and they drop faster but there’s also more safe space to maneuver to.

Oh and, the game art is all mine. Yes, I know … but Man-Spiders do have just six legs! :)