Normalmaps

Normal maps are textures used in 3D computer graphics to simulate fine surface detail by altering the per-pixel lighting calculations. A normal map encodes normal vectors in texture space, allowing lighting to react as if the surface had more geometry than it actually does.

Most normal maps encode the X, Y, and Z components in the red, green, and blue channels respectively. In rendering, each sample value is remapped from [0,1] to [-1,1] to form a normal vector. The Z component is typically the blue channel and most normals point outward, so blue is usually positive.

Normal maps are typically created by baking high-poly details onto a low-poly mesh or painted by hand using specialized tools. They come in tangent-space normal maps, where the encoded normals are relative to the surface's tangent, and in object-space or world-space variants.

Common formats include 8-bit per channel images such as PNG, TGA, or DDS, often combined with standard color spaces. They are used in real-time rendering in games and interactive applications to add microgeometry without increasing polygon count. They work with lighting models such as Phong or physically based rendering (PBR) with appropriate roughness and metalness data.

Limitations include that normal maps influence only shading, not silhouette; they can cause artifacts if the tangent space is not consistently defined across seams; improper gamma or encoding can produce washed-out or noisy results. Compatibility with rendering pipelines and proper mipmapping are important to avoid artifacts at a distance.

History notes: normal mapping was popularized in the early 2000s as a computationally efficient alternative to mesh-detail, and has since become standard in real-time graphics.