iPhone Development: OpenGL ES From the Ground Up, Part 3: Viewports in Perspective
Now that you got a taste of how to draw in OpenGL, let’s take a step back and talk about something very important: the OpenGL viewport. Many people who are new to 3D programming, but who have worked with 3D graphics programs like Maya, Blender, or Lightwave, expect to find an object in OpenGL’s virtual world called a “camera”. There is no such beast.