Minecraft wiki entry for Shaders, associated text: Shaders are written in the OpenGL Shading Language (GLSL). Each single render program comes in two parts, "vertex" and "fragment"; vertex shaders modify the positions of individual vertices, whereas fragment shaders are applied to every pixel. For example, vertex shaders are often used to create waving foliage and water, and fragment shaders can be used to add effects like bloom, god rays, and blur.