Materials, Part 1. Bump Maps, Reflectance Shaders
(version September 16, 2007)
This topic is not isolated to the study of 3D and 3D effects. It has been of concern to graphics artists in the digital age. With 3D software you need to be aware of these issues in order to understand how to get the most from your work. An excellent project may fall flat if you are not aware of details for achieving realistic appearances This is the first article on this topic.
Importance of Bump Maps
Bump maps show up in all 3D software packages for a good reason: this is one way that you get realism. Other types of tools, such as Reflectance maps and Transparency maps also contribute to the overall effect. If you are new to graphic arts or 3D software, you may have escaped hearing about the importance of these techniques. This article is concerned with getting you started in this area. You will not find everything you need to know here: keep reading, keep studying. Look at the manual pages for your favorite 3D product in order to find out all the details about how it handles these aspects of texturing. You are building up as set of tools that you carry around in your head. Take good care of those tools and they will serve you well.
Take a look at the following texture in reduced format from the Marlin Studios Amazing Sci-Fi collection available in the 3D Animation Lab. We will apply this texture to a sphere in two ways: (a) without a bump map, (b) with a bump map. You can see the results below the star cluster image. For our examples of using Bump Maps we are working in trueSpace 7.51. The steps we took were to first apply the image of the galaxy you see directly below to a sphere without a bump map. That is the second picture down below. We then apply a bump map to the same sphere and same texture. That is the third picture down below.
No bump map applied. Take notice of the shiny area of the sphere.
Bump map applied. The sphere is enlarged to enable you to see the results better. Again take a look at the shiny area and compare it to the image right above.
The bump map was created from the original image of the galaxy by brining it into Photoshop and saving it as a grayscale image (just black and white) or alternatively turn the saturation all the way down and save that result. (These two approaches will give you slightly different results.) Bump maps are interpreted by 3D software in the following way: the white areas of the image are the "highest bumps" and the the black areas have no bumps. The gray areas in between as scaled according to how gray the area is. Note that it was not necessary to leave the bump map as it was from the grayscale operation; we could have changed it by creating additional white areas or by blackening some of the white areas in order to change the way that the bumps appear. We chose the easiest method here, but there are many possible ways for us to create a bump map other than the one mentioned here initially.
We were working in the trueSpace modeler in order to do this step. Here is an example of the controls that are available for setting a bump map. We chose a high amplitude value from the Bump panel to exaggerate the effect. The value is 8. In the bump panel below you can also see the grayscale version of the galaxy.
Working with bump maps allows you to add realism to your scene. An additional sense of depth is added to the material applied to your object.
Reflectance Shaders
Reflectance is a very different topic from bump maps. Both of course change the way light interacts with the object surface, and each can bring out realism to your work or stunning effects if you are looking at creating abstract art. Reflectance Shaders allow making the surface of an object simulate a particular kind of material, such as glass or metal. We conclude this sections with some examples of various reflectance shaders for the sphere we were using with the bump map.
Glass Reflectance shader.
Mirror Reflectance shader.
In each of the examples above the same sphere with a bump map is used. The first example simulates a glass surface and the second example simulates a mirror surface. Note from the trueSpace controls (three images up) there are many options on the reflectance shader which can be used to change how this shader works over a wide range of parameters. That concludes our introduction to bump maps and reflectance shaders,
Additional articles will appear in this section.
Topics for further exploration and reading on your own
1. Take a look at the "Leaf Project" available on the Web. This is a very complex and detailed tutorial which talks about using textures and bump maps. You will get a better overall idea by following this tutorial.
2. Where can I find discussions on the web about the issues covered in this article?
3. Practice in 3D software every day. This is the only way you will become an expert.
4. Tell a friend what you learned by reading this article. Show him or her some examples. You will increase your understanding of the topics presented here when you present them to someone else.
We enjoy hearing from you. Some of the questions listed above will appear in future "Topics in 3D" articles. Please send your comments about this article to 
