With Doom3 shipped recently, a lot more games are using normal maps for the real time bump effects. (If you don't now what a normal map is, you can get a sense of it here: http://members.shaw.ca/jimht03/normal.html).

When I saw some Unreal engine 3 screenshots, I decided to try it myself. So I started surfing the web to collect information about normal map, especially how to make and use it in Maya. Very lucky, I found a tutorial at this website (www.drone.org). Then I started my experiment.

I did a layout first to decide my plan. At the very beginning, I thought there were two ways to do it :

Method 1: Model a low-poly character first, layout the basic UVs to eliminate stretching and overlapping, and add details to build the high-poly model. Use the high-poly one to generate a normal map for the low one (see Figure 1).

Figure 1

Method 2: Model a high-poly character first, layout the basic UVs to eliminate stretching and overlapping, then reduce the high one back to a low-poly model. Use the high-poly one to generate a normal map for the low one (see Figure 2).

Figure 2

The benefit of method one is that UVs are defined before you subdivide faces and the final UV boards are exactly the same as those of the low-poly one.

However, people always make mistakes when adding details. Ideally, method 1 sounds perfectly, but what if you found that you deleted edges shared by UV boards? You may find you have to undo 100 times to get back the right UVs. If you are using maya, you may display the UV borders on the mode to make sure that you don¡¯t delete wrong edges. But I don¡¯t know whether other software has the similar tool.