Shaders

Shaders are small programs that run on the graphics processing unit (GPU) to control how a scene is drawn. They are part of the programmable parts of a graphics pipeline and enable per-vertex, per-fragment, per-primitive, or general-purpose computations that determine color, lighting, textures, and other visual effects.

Common shader types include vertex shaders, which process each vertex’s attributes such as position and normal; fragment (or pixel) shaders, which compute the color and other per-pixel data; geometry shaders, which can generate or modify geometric primitives; tessellation shaders, which refine geometry details; and compute shaders, which perform general-purpose computations not tied to the rendering of specific primitives.

Shading languages describe shader programs. The most widely used are GLSL for OpenGL and WebGL, HLSL for DirectX, and Metal Shading Language for Apple platforms. SPIR-V is used with Vulkan and some other APIs. Shaders are typically compiled by the driver, either ahead of time or at run time, and linked into shader programs that are bound during rendering. Programs communicate with the application via uniform values, attributes or inputs, and textures or buffers.

In practice, shaders implement lighting models, texturing, and effects. They enable both traditional lighting approaches such as Lambertian or Phong shading and modern physically based rendering (PBR) workflows. Shader use also extends to post-processing effects, screen-space reflections, shadows, and particle systems. Compute shaders expand capabilities to tasks like image processing, simulations, and data-parallel computations on the GPU. The wide adoption of shaders has made real-time rendering flexible and visually rich across platforms.