Tekstursampling

Tekstursampling (texture sampling) is the process of retrieving color and other data from a texture image using texture coordinates in a rendering pipeline. In computer graphics, surfaces are textured by mapping UV coordinates to texel data stored in texture images. The sampling typically occurs during fragment processing, where a texture unit queries the texture with coordinates derived from the shader and returns a color value applied to the fragment.

Sampling methods control how the texture is read when the source pixel does not align with the texel grid. Nearest-neighbor (point) sampling selects the closest texel. Bilinear interpolation uses the four closest texels to interpolate a smooth value. Bicubic and higher-order filtering use more samples for smoother results but are more expensive. To handle varying distances and reduce aliasing, mipmaps are used: a prefiltered set of progressively smaller textures. Trilinear filtering blends between adjacent mipmap levels; anisotropic filtering further improves quality for oblique viewing angles by sampling along the texture's anisotropy.

Addressing modes determine how texture coordinates outside the [0,1] range are handled. Common modes include wrap (repeat), clamp to edge, and mirror repeat; border color can also be specified for some systems. Filtering modes distinguish between minification and magnification; the GPU selects the appropriate mipmap level using screen-space derivatives.

Artifacts such as aliasing, shimmering, seams, or blur can arise from sampling choices, texture compression, or tiling. Texture sampling is fundamental in real-time and offline rendering, influencing visual fidelity, performance, and memory usage, and is a key component of shading and material workflows.