Basics: Bump and displacement maps
In our continuing series looking at materials and shaders, this issue we focus on bump and displacement maps
We continue our series by exploring two image maps
If you’re new to CGI, you may feel that there are far too many tools to choose from in a dizzying array of software. This series aims to break everything in CGI down to the very basics, so that every artist can be armed with the knowledge of which tool is best. Let’s continue exploring materials and shaders by looking at bump and displacement maps.
In a previous issue’s 3D Basics article we took a look at normal maps, which are a type of image map used to add extra detail to your models.
There are other image map types for adding details and relief to models: bump and displacement maps. These both use black and white imagery to create relief data for a model, making bump and displacement imagery far easier to create and manipulate in any 2D painting application when compared to the complex three-colour arrangement of normal maps.
The differentiation between bump and displacement maps is in how they display the relief.
Bump maps are one of the oldest form of image map types (normal maps are derived from bump maps), and have been used for decades to add surface relief to models. Bump maps are not very resource-intensive making them a popular choice for a wide range of relief work. The catch with bump maps is that they cannot render corner or edge detail, which makes them problematic in certain situations, for example adding brick detail to a corner edge. Bump maps are by far the easiest type of relief image to manage as they work with practically any surface, no matter what the geometry.
Displacement maps, although they can be derived from the same type of image as a bump map, are much more powerful. They can truly deform geometry up to and including edge detail, making them ideal for a much wider range of uses such as terrain creation (sometimes a displacement is called a height map for large-scale deformation) and detail modelling. The reason that displacement maps are not as commonly used is that they can be computationally intensive and they tend to like high-resolution geometry to work with, which can make them less than ideal for some tasks.
Either way, understanding bump and displacement maps will enable any 3D artist to add detail to their models more quickly and intuitively than through other image-based methods.