Figure 1.1: Stylized hair. Image created by and © Bill Fleming.

Is your 3-D character having a bad hair day? There seems to be an epidemic of bad hair on 3-D characters. Of course, it's not the fault of the artists as much as it's the technology. While 3-D programs have come a long way, they have yet to really perfect hair effects. Hair is the defining element of many creatures. Unfortunately, for the 3-D artist, this presents a real challenge since hair and fur in reality are comprised of tens of thousands of tiny fibers.

Therefore, to make hair appear realistic, you literally need to have the same number of fibers on your 3-D character. This can be a real challenge, particularly if you plan to model the hair by hand. Another complication of hair is the fact that it tends to vary in length, density, color and thickness. It can be curly, kinky, straight, wavy or even braided. Plus, there's the hairstyle to consider. Not too many characters look appealing with a "bowl" cut. As you can see, there are many factors to consider in creating hair for your 3-D character. So, how do you go about creating the natural hair look for your characters? Well, let's take a look at the growth of 3-D hair over the years and the many techniques that have evolved along the way.

The Evolution of 3-D Hair
Ten years ago 3-D hair was nothing more than a plastic shell. This is the original 3-D hair, which was rather stylized and cartoony. The hair was created with simple geometry that formed the volume of the hair as shown in Figure 1.1.

Typically, bump maps were used to simulate strands of hair but they were often no more than straight lines, which left the hair looking plastic and plain. This, of course, is a nice look for cartoon characters but there are times when a more natural effect is needed, such as in those high budget Hollywood effects films. Another problem was that the hair couldn't be animated. It just sat there, solid as a rock and lifeless. The good news about this style though was that every 3-D program was capable of creating it. There were some very innovative artists who styled the mesh to create simulated hair styles such as the popular Japanese anime look, which was definitely a good look, but still wasn't animatable. This primitive hairstyle was the only option for many years until 1989 when we made the next leap in technology by developing the Clip Map.

Figure 1.2: A clip map and its color map. Image created by and © Bill Fleming.

Clip Map Hair
A clip map is a black and white image that's used to clip portions of a model. The white areas of the clip map represent the part of the model that will be clipped, or cut off. Figure 1.2 shows a clip map and the accompanying color map for hair.

Using clip maps, we could simulate hair strands by clipping fine lines in a hair mesh. This, coupled with a nice hair image map, made it possible to create relatively realistic hair in still images, like the one shown in Figure 1.3.