Creating Normal Maps: Introduction

Normal maps are an easy way to add the appearance of detail without actually adding the detail. Below are several simple examples of the difference a normal map can make.

No Normal Maps

With Normal Maps

In each example it looks as if the normal map added more physical detail to the 3D model. But it didn't. It's an illusion. The number of faces and vertices didn't change.

What did happen?

Normally when you look at a 3D model, you see light that has been reflected from the surface of the 3D model.

When a normal map is used, the surface of the 3D model isn't used to calculate how the light is reflected. Instead, information provided by the normal map is used. You see light reflected from surfaces that aren't there.

Even though the details you see are an illusion, they have the same highlights and shadows as real details. Change the direction the light is coming from and the highlights and shadows change. Just like they would on real details.

Normal Map Limitations

Details added with a normal map aren't real. They can't cast shadows on other objects. They can't block the view of other objects. The outline of a 3D model with a normal map looks exactly the same as the 3D model without the normal map.

If a camera is placed so it looks along the surface of the 3D model, the illusion of the details disappear.

Look along the surface (top) and the
illusion disappears.