How to Generate PBR Maps: Complete Guide to Normal, Roughness, Metallic

Introduction

Physically Based Rendering (PBR) requires a specific set of maps to accurately simulate real-world materials. Among them, Normal, Roughness, and Metallic maps are the most essential components. This tutorial will guide you on how to generate these maps.

Normal Map Generation

Normal maps store surface normal direction, used to add visual complexity of geometric details. Generation methods include:

Baking from High-Poly Model

Use modeling software (such as Blender, Maya, ZBrush) to bake high-poly model details onto a low-poly model.

1. Create low-poly and high-poly models.
2. In Blender, select the low-poly model, enter the Shading workspace, add an Image Texture node, and create a new normal map.
3. Use the "Bake" function of the Cycles renderer, set Bake Type to "Normal", and select the high-poly model as the target.
4. Bake to obtain the normal map.

Generating from Photos

Use normal map generation tools (such as CrazyBump, ShaderMap, AwesomeBump) to generate normal maps from diffuse maps or height maps.

1. Import a color texture or grayscale height map.
2. Adjust parameters such as strength and blur.
3. Export the normal map.

Procedural Generation

In node-based tools like Substance Designer, combine noise, shapes and other nodes to generate normal maps.

Roughness Map Generation

Roughness maps control the micro-roughness of the surface, affecting the blurriness of reflections. White indicates rough (strong diffuse reflection), black indicates smooth (strong specular reflection).

Extracting from Photos

1. Open a surface photo in an image editing software (such as Photoshop).
2. Convert to grayscale, adjust contrast so rough areas are brighter and smooth areas are darker.
3. Use high-pass filtering or inversion to extract roughness information.

Procedural Generation

In Substance Designer, use Grunge Maps, Noise and other nodes to generate roughness variation, combined with blend nodes for control.

Manual Painting

For specific materials, manually paint roughness in texture painting software (such as Substance Painter, Mari).

Metallic Map Generation

Metallic maps specify which areas are metal (white) or non-metal (black), usually only 0 or 1, but gray values can be kept for transition areas.

Creating Masks from Photos or Textures

1. Based on material properties, use selection tools or color range to select metal areas.
2. Fill with white, and fill non-metal areas with black.
3. Use feathering or gradients for transition areas.

Procedural Generation

In Substance Designer, use ID maps or material blending to define metal areas.

Manual Painting

In Substance Painter, use fill layers and masks to precisely control metalness.

Tool Recommendations

• **Blender**: Free and open-source, supports baking normals from high-poly.
• **Substance Suite**: Industry standard, offers Designer and Painter with powerful procedural and hand-painting capabilities.
• **CrazyBump / ShaderMap**: Designed for generating normal, roughness and other maps from photos.
• **Materialize**: Free tool that can generate multiple PBR maps from a single photo.
• **AwesomeBump**: Open-source alternative.

Notes

• **Color Space**: Normal maps should use linear color space; roughness and metallic maps usually use linear or grayscale, avoiding sRGB correction.
• **Map Resolution**: Decide based on target platform and model complexity, typically 1024x1024 or 2048x2048.
• **Seamless Tiling**: If the material needs to tile, ensure the generated maps are seamless.
• **Consistency**: Ensure all maps are aligned with consistent texture coordinates.

Summary

There are multiple methods to generate PBR maps, choose according to project needs and resources. Baking from high-poly offers highest quality but is time-consuming; generating from photos is fast but limited in accuracy; procedural generation is flexible but requires expertise. It is recommended to combine multiple methods.