Lighting in 3DCG: Understanding the map

This article describes each map used in 3DCG and its purpose.

In this article, I will create a normal map in Photoshop and check how it looks in Maya.

This article has been written for people who have heard of the various “maps” but do not know much about them.

What is a map?

It is a type of 3D model texture that can simulate material-like shadows, details, and highlights.

There are several types of maps, including normal maps, bump maps, height maps, displacement maps, and specular maps.

There are other types of maps, but I will describe the above maps which are mainly used in 3DCG.

Bump Map

Bump mapping = a map that represents a bump 

Bump map is a grayscale image that determines the direction of the normals of a pixel based on the height difference of the 3D model.

As this is a grayscale image, it only has information on color brightness (white or black). Since the normal direction of the pixels is automatically determined, the values are relative.

It does not calculate external factors such as lighting like normal maps.

As a side note, height maps are also a type of bump map. It stores information in which the whiter they are, the higher they look, and the blacker they are, the lower they look. In other words, black and white shading holds the height information for each pixel.

Normal map

A normal map is also called a normal map which indicates the normal direction of the geometry.

Based on this vector information (normal direction information), the reflections and lighting of the 3D model are reflected. Therefore, it is recommended to use this map for real-time rendering.

Normal maps and height maps are included in the Bump Map category, but they have different data storage information. Normal maps differ from bump maps in the presence or absence of vector information.

Displacement map

Displacement maps are used for silhouettes that represent surface detail (e.g. skin irregularities). They can be directly reflected in the geometry.

The procedure is essentially the same as for bump maps, except that you can reflect the geometry.

Creating a displacement map in advance with sculpting software makes it easier to maintain detail in later processes such as rigging and animation.

Specular Map

This is also known as a specular reflection map.

This map can represent the amount of luster of the 3D model – it expresses “shine”.

It can express the shine of a 3D model face when it is being made up (the shiny areas of highlights and eye shadow). It can also be used to create reflections in certain areas such as sweat.

Advantages of Maps

The purpose of a map is to reduce rendering time and processing load.

Once you understand the purpose of a map, you can kind of see the benefits of maps. Normally, the number of polygons increases when modeling includes a small amount of unevenness.

The higher the number of polygons, the more time is needed for rendering. Therefore, when you move 3D objects with detailed mesh structures in a game or animation, the processing load becomes high.

To reduce rendering time, you can use maps to create pseudo-detail on the surface of a 3D model instead of creating detailed shapes with more polygons.

Creating a normal map (normal map) in Photoshop

In this article, I will create a normal map that is affected by light. Check it out because it’s easy to do in Photoshop.

Specific instructions on how to create it in Photoshop can be found in this article.

 

Here is the normal map we were able to create this time.

Creating a normal map

Creating a normal map

By the way, here‘s the texture I used this time.

Check it out in Maya!

Check the normal map we have created in Maya.

As we saw in the previous section, the normal map is affected by light, so let’s see how different it is with and without lighting.

On the right is an image with a normal map.

You can see the difference between a normal map and one without lighting. If you move the light, the normal map will look different, so it is convenient.

Left: No normal map Right: With a normal map

Left: No normal map Right: With a normal map

 

Summary

Finally, here’s a summary of the map.

Bump Map

A grayscale image that uses the height difference information of a 3D model to determine the direction of its pixel normals.

Normal and Height Maps are a type of Bump Map

Normal map (Normal map)

Bump maps differ from bump maps in that they show the normal direction of geometry.

Height Maps

The whiter the area, the higher the visual height, and the blacker the area, the lower the stored information.

Displacement Map

It can be used in silhouettes to represent surface detail, such as the silhouette of a surface (visual irregularities), and can be directly reflected in the geometry.

Specular map

Allows you to express the amount of gloss on a 3D model. It can express shine.

What did you think?

There are many different types and uses for maps. Understanding the characteristics of each map will help you to work more efficiently.

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