Another Great Cocos2D Tool: PhysicsEditor

On March 15, 2011, in cocos2d, tools, by Steffen Itterheim

In my book I explained how to create collision shapes for physic engines using the freely available version of VertexHelper Pro. Granted, it works, but as soon as you need to update your shapes frequently or you have many different shapes to edit it’s going to be a lot of manual work and error-prone copy & paste between VertexHelper’s code generator and your source code.

VertexHelper, meet your replacement: PhysicsEditor

PhysicsEditor was written by Andreas Löw, the author of the very popular TexturePacker tool. He has proved again that he can create powerful yet easy to use tools for game developers.

The greatest part about PhysicsEditor: it can automatically trace your shapes to generate collision shapes and it works flawlessly! You can even tweak the amount of vertices (and a lot of other things) as needed, for example if your physics engine has a limitation on how many vertices can be used for a collision shape (Box2D default: 8 vertices).

But it doesn’t just create the collision shapes, it also allows you to edit physics properties of a shape that often go along with it. Density, friction, “bouncyness”, and other parameters can be tweaked in the GUI.

As they say, an image speaks louder than words, so I suppose a video speaks in a thousand images:

Not just Cocos2D

PhysicsEditor currently exports to Cocos2D + Box2D (Chipmunk/SpaceManager support is forthcoming and should be available soon) and also to Sparrow Framework + Chipmunk and of course Corona SDK.

And it works on Windows, too! Which makes sense given that Corona supports Android development under Windows.

I also found this post about PhysicsEditor with a working Flash example (at the bottom). It seems that even exporting respectively using PhysicsEditor with Flash + Box2D seems to work well. Wow!

Brace for impact!

Check out the PhysicsEditor Features page to learn more about what this great tool can do for you! You can get PhysicsEditor alone for $17.94 but you can also grab a bundle deal which includes TexturePacker for $29.99, or almost 20% off.

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The Ultimate Cocos2D Project: Libraries

On March 4, 2011, in cocos2d, Kobold2D, by Steffen Itterheim

The Ultimate Cocos2D Project is: Kobold2D!

Put simply: Kobold2D is designed to make Cocos2D developers more productive.

Original Post

Last week I wrote that I’m Building The Ultimate Cocos2D Xcode Project. In today’s weekly update I wanted to give you some more details on the use of libraries in that project.

Cocos3D included

So there happens to be a Cocos3D now. Rather than being part of the Cocos2D distribution, it’s an extension project. Guess what that means? Right, installing Cocos3D means fumbling with the dreaded install-templates.sh script (see this Cocos3D tutorial). Of course the first user reactions were: how do I install it? Installation failed, what am I doing wrong? And so on …

The Ultimate Cocos2D Project wouldn’t be ultimate if it didn’t include Cocos3D out of the box. And unmodified of course, as with all included libraries I want to make it as simple as possible to replace one library version with another. Once you get to half a dozen of included libraries, maintaining them all can become a hassle, so the very least I can do is to make it easy for everyone to upgrade specific libraries.

Obviously: Cocos2D included

Of course Cocos2D is also included as a static library as opposed to cluttering your project with all of its source files. Xcode project references make it very convenient to add external code and keeping it seperate. I’ve described the process in detail in my Cocos2D Xcode Project tutorial but since then I’ve learned a couple more things about how to make this even better.

For example, I no longer include cocos2d-iphone directly, instead there’s a seperate Xcode project in between so that I have full control over build settings (using XCConfig files) and make it possible to build both iOS and Mac OS targets in the same Xcode project. I will also include the current version of Cocos2D in the download because my goal is to make everything work out of the box.

No fumbling with install scripts, no additional downloads necessary, no need to modify any Xcode build settings – including developer certificates and header search paths. Build configurations for Ad Hoc and App Store release builds are also included, which will create .IPA and .ZIP files for you ready for Ad Hoc distribution respectively upload on iTunes Connect.

Popular libraries included

Now let’s get to the juicy part. Early on I realized that Cocos2D users often needed (or wanted) to include other libraries. Some of them have become so popular among the Cocos2D crowd that they could as well be part of the official distribution. Alas, they’re not. That’s a service I want to provide.

Often those libraries require special and non-obvious steps to successfully add them to an existing project. All too often those steps are either undocumented, untested, hard to follow, refer to outdated versions of Xcode, iOS SDK, etc. and generally require technical expertise of project configuration and compiler settings.

This is all taken care of for you. Here’s the list of libraries that are already included in the Ultimate Cocos2D Xcode Project:

That is quite a list. All you need to do to use these libraries is to either enable them in code or merely include the header file and start using them. If you worry that all these libraries will bloat your App, rest assured that Xcode is very clever: if you don’t actually make use of a static library (eg don’t include any of its header files), it will not be linked with your App and not waste any space or performance. I verified that.

Update policy

These are a lot of libraries to keep up to date. I plan to make about 4-8 point releases each year, usually triggered by a major (speak: non-beta) release of Cocos2D. If updating other libraries justifies an update depends on the library’s importance and the significance of the update.

Your libraries

Adding your own libraries to the project will be easy and the process will be documented. This will encourage code-sharing because your library will just work with other user’s project, it only needs to follow a few simple guidelines to become plugin-capable. This opens the door for better and tighter integration of 3rd party code into your projects. Even if you don’t intend to share your code, you’ll still benefit because your code will be easier to re-use and maintain.

Also, if you like you can make a request for a specific library or additional source code that should be included in the project, please leave a comment. I’ll see what I can do. :)

cocos2d Book, Chapter 13: Physics Game

On September 20, 2010, in Announcements, book, cocos2d, by Steffen Itterheim

Chapter 13 – Physics Game

After the introduction of the physics engines Box2d and Chipmunk, this chapter will focus on one physics engine in greater depth by making a physics game using Box2d.

What kind of game? If you have an idea real quick let me know, because I haven’t decided yet. I was thinking about a space game with gravity but also a bit like Pinball, or more like a Sandbox game with some optional goals. Or something else entirely. The only caveat is: it has to be do-able in less than a week while also writing the chapter and I should be able to illustrate some details about the physics engine! That’s no mean feat.

Summary of working on Chapter 12 – Physics Engines

I basically split this chapter in half and gave each of the two physics engines, Box2d and Chipmunk, a good treatment. Initially I started with the templates provided by cocos2d, just to get all the code together and not having to talk about setting up the Xcode project. I quickly realized that the application templates are inadequate, erroneous and outdated, probably because they have barely been maintained as both Box2d and Chipmunk matured. They seriously need a refresher, and I was thinking that maybe I’ll turn the two projects for this chapter into cocos2d application templates for physics engines, replacing the current ones and using my Xcode template project, so that I don’t need to go in and change them every time cocos2d gets an update.

Anyway, both physics engines got their treatment and I built the same project for both. So now you can actually compare them, side-by-side, be it performance or behavior or just plain coding style or number of lines.

Unfortunately, there’s a lot to talk about even for just doing the basics. I got both projects to the point of adding more boxes to the world, then adding rudimentary collision detection and a simple joint example with 4 bodies strung together. There wasn’t enough space for more. But I did foresee it which is why I planned in the Physics Game chapter as a follow-up. Let me know real quick if you have an idea for a simple physics game, or send me a link to an existing game on the App Store. Ideally within the next 24 hours.

My Opinion

I once again realized why some developers may be preferring Chipmunk because it is more “direct” and easier to pickup, as in you just add a new callback method and that’s that. I can see that but it’s very misleading. Chipmunk is making me cry by throwing all those one-letter e, u, i, f, m, p, etc. fields at me, so I’ll have to remember that u is for friction, for example. I’m not a machine! And because you can’t hide private fields in C those are exposed as well, adding to the confusion. I found myself having to look up a lot of things frequently in the Chipmunk manual. The bad thing is, it’s a manual, and not an API reference – but I keep having to use it like it were an API reference by using search a lot. Box2d provided a much cleaner API and both a manual and an API reference, which made it a lot less painful to figure things out, to look things up.

People’s arguments about which physics engine is better often runs along the lines of language, features, performance, memory footprint and what not. But if I have to choose, I’d say both are fairly complete and mature physics engines, so for me the choice is really about API design and documentation. And in that area, Box2d is the clear winner in my book. Of course, I kept a neutral tone writing the book, I don’t want to bias anyone because at the end of the day, the important thing is that you can make a great game with both engines, and not everyone is familiar with C++ and that’s a very daunting language to learn.

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Chapter 12 – Physics Engines: Box2d & Chipmunk

This chapter gives you an introduction to physics engines and what they can do. Since cocos2d supports two physics engines out of the box, Box2d and Chipmunk, I will explain how to do the same things in both physics engines and I aim to cover at the very least the basic elements like shapes, joints and collisions.

Because choosing either physics engine is often done on subjectively. Some developers may prefer the Object-Oriented C++ nature of Box2d while others may feel more comfortable with the C-based interface of Chipmunk (*). At the very least I want to present both and show their strength and weaknesses by example.

(*) Note: there is an Objective-C binding for Chipmunk made by Howling Moon Software. It’s free to use on Mac OS X and iPhone Simulator but costs $200 per title if you want to publish to the App Store. I believe that most cocos2d developers wouldn’t mind spending up to $30 on a tool or library that is essential, that is why I included Zwoptex and Particle Designer in the book. This product however is in a different ballpark price-wise.

On the other hand, the free Chipmunk SpaceManager also aims to offer better integration with cocos2d-iphone and promises a simplified Objective-C interface. I will have a look at the SpaceManager and then decide whether I’ll discuss it in the book, I say it’s likely. Another physics tool that has gotten some attention is the VertexHelper which I’ll at the very least will refer to.

Summary of working on Chapter 11 – Isometric Tilemaps

Isometric tilemaps rock! That is, if you can get all those nasty issues solved. Even though all the issues like graphics glitches at tile edges, correct z-ordering and the proper blend functions have all been discussed and solved by now, it’s still very challenging to get an isometric tilemap on the screen and a player walking over it, with no glitches at all. I believe this chapter will give a lot more developers the chance to delve into the exciting world of isometric tilemaps. I too learned a lot making this example game, and part of me now wants to write an old-school isometric RPG game. Again. For the n-thousand-th time. Sigh. Some day, some day …

Anyhow, the project I made over the course of this chapter features properly z-ordered tiles and a player sprite, which moves tile-by-tile over the isometric tilemap. You control the player by simply touching in the direction relative to the player that he should move to. One specialty of this project is that the player always remains centered on the screen, he doesn’t move at all! It’s simply the tilemap that is moved under him, which makes a couple things much easier.

Nevertheless you also learn how to find the tile coordinates for a tile that you touch on the screen. And how to avoid the isometric, diamond-shaped tilemap to show the “outside” of the world by adding a border around the tilemap and limiting movement to the playable area. Similarly, the blocking tiles like walls, mountains and houses all block the player’s movement by drawing over the map with a collision layer and a tile whose property is set to “block_movement”.

In the meantime, if you want to gain a better understanding of how isometric tilemaps work, I can recommend the Isometric Projection article by Herbert Glarner. And in case you’re wondering how I suddenly and dramatically increased my art skills, I’ll be honest: I didn’t. I used the terrific tilesets from David E. Gervais which are published under the Creative Commons License. It means you are free to to copy, distribute and transmit those tiles as long as you credit David Gervais as their creator. You can download these tiles from Pousse Rapiere’s website or you can directly download them all at once as 6.4 MB ZIP file here. If you like to hear it from the man, here’s a bit of insight and history from David explaining how these tiles were made.

I made a few additions to the Xcode Tutorial and the cocos2d FAQ which are based on user questions and concerns.

Xcode Project Tutorial: How to integrate Chipmunk SpaceManager

How to update the cocos2d-iphone code in a project created with a cocos2d Project Template? (Theory & Advice)

How to fix common Box2d compile errors? (must compile using C++)

How to fix common Chipmunk compile errors? (does not compile with C++ code)

How to draw an endlessly repeating Parallax Background? (very simple, very effective)


On Searching the Tutorial & FAQs

I’m still trying to get the search function on the Tutorial and FAQ pages fixed. Currently it works for the Xcode Tutorial only but other search result links may simply show an Error. I’ll try to get this fixed as fast as i can and i’m getting very helpful support from the folks at ScreenSteps Live so i’m hopeful.

Please also note that the search box in the navigation panel doesn’t search the FAQ and Tutorials, just the blog and pages.

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