I want to develop a 2d game. I have to choose from Quartz/CoreGraphics, OpenGL ES or Cocos2D. I'm interested in how the game Pocket God is realized because it fulfills perfectly my needings.
Do you know which technology is used to build the game Pocket God?
Developer Dave Castelnuovo mentions OpenGL in the touchArcade forums.
According to Dave Castelnouvo (Creator of Pocket God) they built their own engine using the standard iPhone SDK.
If you are interested in using their engine you will have to contact Dave at Bolt Creative to see if they are willing to license it out.
However there are a number of publicly (but not free) engines around for building iPhone games. I would start with one of those before going after a non-public one.
If your goal is to build a 2D game for the iPhone, just use Cocos2D (or another high level game engine). If you have issues working with third party libraries, use CoreGraphics. If your goal is to be a graphics programming expert, go with OpenGL.
In general terms, Cocos2D is built on CoreGraphics which is built on OpenGL. You could accomplish all the graphics in Pocket God by directly using OpenGL, but it would be much harder than just using the higher level graphics package. Each package abstracts and simplifies using the lower level package.
You have more control and a broader range of possibilities when using the lower level packages, but you also need a deeper understanding of the fundamentals of computer graphics programming.
One caution when using the higher level package is that trying to do something that stretches the capabilities of the package, adding that unique graphic effect to your game for example, will require learning the lower level package anyway. Your choice is either to abandon that extra feature or climb another learning curve.
The official answer given to me by email is:
We actually use openGL because it’s the most flexible, we wrote our own engine and to not use and libraries to handle anything.