What is a Normal Map?

In 3D computer graphics, a Normal Map is a texture mapping technique used for faking the lighting of bumps and dents – an implementation of bump mapping. It is used to add details without using more polygons.

How Does it Work?

A normal map uses RGB information to correspond directly with the X, Y, and Z axis in 3D space. This RGB information tells the 3D engine the exact direction the surface normal is facing for each pixel.

• Red Channel (R): Left/Right (X Axis)
• Green Channel (G): Up/Down (Y Axis)
• Blue Channel (B): Forward/Backward (Z Axis)

This is why most Normal Maps look predominantly purple (or periwinkle blue), because the "normal" direction (straight out from the surface) is represented by the Blue channel.

Normal Map vs. Displacement Map

While both are used to create surface details, they work very differently:

Normal Maps are an illusion. They change how light interacts with the surface, but the silhouette of the object remains flat. They are extremely performant and perfect for fine details like pores, scratches, and fabric weave.

Displacement Maps (Height Maps) actually alter the geometry of the mesh. They require more processing power (tessellation) but provide true depth and can change the silhouette of the object.