Normal Map
A texture that encodes surface normal directions as RGB color values, enabling per-pixel lighting calculations that simulate geometric detail on low-polygon models in real-time rendering.
A normal map stores surface normal vectors encoded as RGB color data. Each pixel's R, G, B channels correspond to X, Y, Z normal components. The renderer uses these per-pixel normals for lighting, creating the illusion of surface detail on flat polygons.
- Tangent space: Most common format, storing normals relative to the surface. Flat areas appear blue-purple (RGB: 128, 128, 255). Works correctly on deforming meshes
- Object space: Stores absolute normals in local coordinates. Rainbow-colored appearance, suitable for static objects with slightly better quality
- Baking from high-poly: Normal information from million-polygon sculpts is transferred onto low-poly game meshes using xNormal, Substance Painter, or Marmoset Toolbag
- Generation from height maps: Grayscale height maps converted via Sobel or Scharr filters that compute surface gradients
Applying a 2048x2048 normal map to a 100,000-polygon model simulates tens of millions of polygons at 60fps. DirectX and OpenGL use opposite Y-axis conventions (green channel inversion), requiring attention when transferring assets between engines.