Chapter 16

Drawing with Quartz and OpenGL

Every application we've built so far has been constructed from views and controls that are part of the UIKit framework. You can do a lot with the UIKit stock components, and a great many applications can be constructed using only these objects. Some applications, however, can't be fully realized without going beyond what the UIKit stock components offer.

Sometimes, an application needs to be able to do custom drawing. Fortunately, we have not one, but two separate libraries we can call on for our drawing needs:

• Quartz 2D, which is part of the Core Graphics framework
• OpenGL ES, which is a cross-platform graphics library

OpenGL ES is a slimmed-down version of another cross-platform graphic library called OpenGL. OpenGL ES is a subset of OpenGL, designed specifically for embedded systems (hence the letters ES), such as the iPhone, iPad, and iPod touch.