texel

A texel, short for texture element, is the fundamental unit of a texture in computer graphics. Like a pixel for on-screen images, a texel represents a single sample of a texture and stores color data (and sometimes additional channels such as an alpha value). Textures can be 2D, 3D, or arranged as texture arrays, and texels map to fragments during rendering.

A typical 2D texture is a grid of width by height texels. Each texel holds color information in a chosen format, such as RGBA8, RGBA32F, or a compressed block format. Textures may be stored in linear or sRGB color spaces and can include mipmaps, which are prefiltered versions at different resolutions to improve sampling when the texture appears smaller on screen.

Texel sampling uses coordinates in texture space. TexelFetch accesses a texel by integer coordinates, while sampling with normalized coordinates (u, v) in the range [0, 1) retrieves color values through filtering. Filtering modes determine how texels contribute to the final color: nearest-neighbor uses a single texel, while bilinear, trilinear, or anisotropic filtering blends multiple texels to reduce artifacts.

Memory layout and formats vary by hardware, including uncompressed formats and compressed ones such as BC/DXT. Texture units perform sampling in shaders, enabling a wide range of effects from diffuse textures to normal maps and height maps. Mipmaps provide different levels of detail to maintain performance and visual quality during minification.

Texel density describes the number of texels per unit area on a surface and is a common consideration in texture work. While related, texels exist in texture space, whereas pixels exist in screen or image space.