Normal Maps

Summary

Normal maps must be in DirectX format (green channel inverted if from OpenGL), as GTA V uses DirectX rendering.

This section covers normal map creation, conversion, testing, and optimization for realistic lighting effects.

Normal maps use RGB colours to simulate surface details (e.g., bumps, scratches) by altering light direction, adding depth without extra polygons. In GTAV, they’re vital for realistic clothing folds, vehicle scratches, or prop textures.

DirectX vs OpenGL Format

• DirectX: Red (X-axis), Green (Y-axis, downward), Blue (Z-axis, outward).

• OpenGL: Green channel points upward, requiring inversion for GTA V compatibility.

• Conversion Steps:

  1. Open the normal map in Photoshop.

  2. Select the Green channel (Window > Channels).

  3. Invert it (Image > Adjustments > Invert or Ctrl+I).

  4. Save as DDS with DXT5 compression (supports alpha if needed).

In Game Appearence Challenges

• Normal maps often look stronger in GTA V than in tools like Substance Painter due to differences in lighting models.

• Solution: Adjust the bumpiness value:

  • Low (0.1-0.3): Subtle details (e.g. fabric weave).

  • High (0.7-1.0): Pronounced features (e.g. deep scratches).

Creating Normal Maps

1. Use Substance Painter, Blender, or Photoshop’s NVIDIA plugin to generate from a height map.

   1. Manual Editing: Paint RGB values directly (Red = left/right, Green = up/down, Blue = depth).

2. Ensure DirectX format before export.

Best Practices

• Resolution Match: Use the half the resolution as the diffuse map.

• Avoid Overuse: Too-strong normals can look unnatural; test at various lighting angles.

• Compression: DXT5 for quality, though DXT1 works if no alpha is present.