The shader environment

Other applications that you might have coded in the past are built to run inside a CPU. This means that you have used a compiler that took your program (programmed in your favorite high-level programming language) and compiled it down into a representation that a CPU could understand. It does not matter if the programming language is compiled or interpreted, because in the end, all programs are translated to something the CPU can deal with.

Shaders are a little different because they are meant only for graphics, so they are closely related to the following two points:

• First, they need a graphics card, because inside the graphics card lies the processor that will run them. This special kind of processor is called the GPU (Graphics Processing Unit).

• A piece of software to reach the GPU: the GPU driver.

Tip

If you are going to program shaders, the first thing that you have to do is prepare your development environment, and that starts by downloading, and always keeping your graphics card driver updated.

Now suppose you are ready to start and have your first shader finished. You should compile and pass it to the GPU for execution. As GLSL relies on OpenGL, you must use OpenGL to compile and execute the shader. OpenGL has specific API calls for shader compilation: link, execution, and debug. Your OpenGL application now acts as a host application, from where you can manage your shaders and the resources that they might need, like for instance: textures, vertices, normals, framebuffers, or rendering states.