What is a Normal Map in Blender?

A Normal Map is a technique used in computer graphics to represent the fine details of a surface. This map stores the normal vectors of each pixel of a 3D model's surface, determining how light reflects off the surface. This allows a flat surface to appear as if it has complex textures and details.

Key Features of Normal Maps

• Normal Vector Storage: Stores the normal vectors of each pixel as RGB values. The R, G, and B values represent the X, Y, and Z axes of the normal vector, respectively.
• Detail Enhancement: Enhances surface details without adding actual geometry.
• Performance Optimization: Improves rendering performance by representing high-resolution textures without complex modeling.

Uses of Normal Maps

• Game Graphics: Used to realistically depict the textures of characters and environments.
• Movie VFX: Enhances the realism by representing complex surface details.
• 3D Modeling: Adds details to models.

 

The left UV Sphere shows the appearance without the Normal Map applied, while the right UV Sphere shows the appearance with the Normal Map applied. You can see a significant difference in the sense of depth.

DX and GX in Normal Maps

DX and GX refer to DirectX and OpenGL, respectively. The main difference between the two is the direction of the normal vectors.

DirectX (DX) Normal Map

• Normal Vector Direction: In DirectX, the Y-axis of the normal vector points upward.
• Usage Environment: Primarily used in Windows-based applications.

OpenGL (GX) Normal Map

• Normal Vector Direction: In OpenGL, the Y-axis of the normal vector points downward.
• Usage Environment: Used across various platforms, especially in game engines and graphic software.

Summary of Differences

• Normal Vector Y-axis Direction: DirectX uses Y+ (upward), OpenGL uses Y- (downward).
• Compatibility: Depends on the graphic API being used. The correct format must be used for the application to function properly.

In Blender, it is common to use the OpenGL format for Normal Maps. This is because Blender is primarily based on OpenGL. Therefore, you should use a format where the Y-axis of the Normal Map points downward.

Setting Up Normal Maps in Blender

1. Create a Texture Node: Load the Normal Map image.
2. Set Color Space: Set the color space of the texture node to Non-Color.
3. Connect Nodes: Connect the color output of the texture node to the input of the Normal Map node.
4. Link Normal Output: Connect the normal output of the Normal Map node to the shader node's normal input.