In the previous section I explained the diffuse map and how to set a bitmap for it. The next step in creating convincing materials is to add texture with bump maps.
Below is the cube that we applied a diffuse map to in the last segment. Viewed at a distance in MAX's default lighting it doesn't look too bad; after all it's just a flat tile surface. In the real world though the tiles are set and held in place with grout; each tile is a raised surface. Applying a bump map to the material will give the appearance of each tile being raised without adding to the geometry of the model. For this lesson I chose a simpler texture.
Bump maps apply texture to a material by using the light and dark values of the bump map image. Dark areas of the image will be rendered as recessed, while light areas will be raised.
This screen shot shows the cube with the bump map applied
As you can see in the rendering by examining the shadows and highlights, the light colored circle is raised while the dark one is recessed.
Like diffuse maps bump maps are often bitmap images. To select the image you want to use for your bump map you have to open the Maps roll-out in the materials editor. I'll assume that if you are trying to learn to make your own materials you already know enough about MAX to understand roll-out menus.
Once you have opened the Maps roll-out scroll down to the Bump Map and click the button to the left of the spinner window that says "none". That will open your Material/Map Browser again and allow you to select the sub-map image for your bump map the same way you did for the diffuse map. For the example cube above I selected an image I made in Photoshop.
After you have selected a map to use as a bump map image you can adjust the bump parameters to further affect the appearance of your material. There are three important bump map parameters you can adjust from the Maps roll-out (they can also be applied to the other maps in use for your materials). The check box to the left of each map type turns the map on or off. To the right of the map type is a window with a set of spinner arrows; this window is used to set the strength or intensity of your map. And to the right of the spinner window is the sub-map selection button you used to set your bump map image. The on/off check box should be a pretty straight forward concept so I won't bother to explain that one. There are a lot of other parameters that can be adjusted for the sub-maps you choose for your bump maps, but I will go over those in a later tutorial.
That leaves the spinner window to explain. I'll be brief. As I explained above the default in MAX is to interpret light areas of a sub-map as raised and dark areas as recessed. With the spinner window you can adjust or change that. The default setting for the strength of a bump map is 30; increasing the number in the window will increase the difference between the light and dark areas, make it bumpier. If you adjust the spinner to a negative number it will reverse the map interpretation. This is especially handy if you are prone to forgetting whether dark colors appear raised or sunken while making your own maps.
Both cubes have the same bump map. However, the map for the cube on the left has a strength setting of 500 while the map for the cube on the right has a setting of -500.
That covers the basics of applying bump maps to materials. There are a lot of maps, settings, options, and tricks that go into making materials. I don't plan to write a tutorial for every one (partly because it takes away the fun of exploring them on your own and making new discoveries, and partly because I haven't learned all the tricks yet myself), but in part 3 I'll try to explain specular highlights and reflect maps. After that, opacity maps, and then using these few basics to make your own custom materials, and putting your new materials into a custom libraries. This ends part 2, so go take a break from the computer, and then come back and practice to see if you learned anything.
Dxyner
This tutorial, all text and images contained herein, and all banners and logos are (c) Flaming Ball -o- Death Designs 2001
