What's the difference between bump, normal, and displacement maps in 3D?

Question

Bump maps give the illusion the surface has depth using grayscale values to drive the map. Normal maps, on the other hand, are considered a newer and more widely used method of achieving a similar effect as bump. Normal maps, however, use RGB (Red, Green, Blue) to drive depth values but again do not change actual surface heights. Finally, displacement maps are used to displace surfaces using grayscale (scalar) or colors (vector displacement). Both displacement methods show a change in the actual surface that can be seen simply by looking at the silhouette of the asset.

Answer 1

All three types of maps have similar end products, but do so with different methods and with some distinct differences.

Bump Maps and Normal Maps are the two most similar. Both are used to provide fake depth information within the bounds of the 3D model itself. By within the bounds of the mesh I mean the texture maps won't affect the actual geometry of the mesh and thus doesn't change the silhouette of your model.

Bump maps are grayscale while Normal Maps are using RGB values. Both simulate the smaller details on your model like skin pores, small wrinkles in clothing, cracks, and other depth information on the model.

Without getting too technical with Normal maps, the RGB values dictate how light is reflected off the surface depending on the direction of the light. Here's what each of the color channels do:

1. The Red Channel shows how the object should look when lit from the right.
2. The Green Channel shows how the object should look when lit from above.
3. The Blue Channel shows how the object should look when lit from the front.

Displacement maps are also for providing depth information from a grayscale texture on the surface of the model, but what makes displacement different is its ability to actually "displace" or move the verteces of the model. Essentially you could take a displacement map of a gravel road with different sized rocks and pebbles and apply it to a semi-high resolution mesh, but completely flat mesh and the verteces of the mesh would move/displace once rendered.

Answer 2

It's simple to differentiate between the three really.

Bump maps are greyscale textures you map onto objects to create the illusion of surface relief (elevations & depressions) on an otherwise flat object. With this type of map, the depressions & elevations appear/look real since they don't truly alter the geometry of a surface which is what happens with Displacement maps.

Normal maps are a type of transfer map. This means the texture is created from a polygon object. There are distinct types of transfer maps which handle the conversion from polygons to textures differently. For example, a normal map captures the surface normal information of the source mesh and uses it to light the targeted mesh.

Displacement maps are grayscale textures which one maps onto objects in order to create true surface relief (elevations & depressions) on literal flat objects, The perfect example of this type of map is how it is used to create terrain maps for animations and even game environments rather than manually modeling the entire world terrain (think of maps like GTA and all the shooter games with large maps for sniper's).

Answer 3

Bump Maps are the older way of adding detail to low poly objects and are used in the same way as normal maps, except they only contain height information and not angle information. Displacement Maps actually displace or move Vertices of a mesh. An example of a displacement map would be how terrain is generated from a texture.