Normal Map
Per-pixel surface detail
Definition
A normal map is a texture that stores per-pixel surface direction (the normal vector) of a high-resolution mesh, baked onto a low-resolution mesh. Each pixel encodes an XYZ direction in RGB channels, letting the shader light a flat polygon as if it had millions of bumps and grooves. Normal maps are the single most common technique for adding detail without polygons, used universally in real-time game art since the mid-2000s.
In production
In a typical workflow you sculpt detail in ZBrush, bake the high-poly's surface direction onto the game-ready low-poly in Marmoset Toolbag or Substance Painter, and the low-poly model carries the visual complexity of millions of polygons at a fraction of the cost. Tangent-space normal maps are the most common variant; object-space normals appear in stylized or rigid-mesh pipelines.
