In this chapter, we will learn how to use Open Graphics Library (OpenGL), a powerful rendering Application Program Interface (API), and combine it with Qt. OpenGL is a cross-language, cross platform API for drawing 2D and 3D graphics on screen through the Graphics Processing Unit (GPU) within our computer's graphics chip. In this chapter, we will be learning OpenGL 2.x instead of 3.x, because the fixed-function pipeline is easier for beginners to grasp compared to the newer programmable pipeline. Qt supports both versions, so there should be no problem switching over to OpenGL 3.x and above once you have learned the basic concepts of OpenGL rendering.