PART 1 - GENERATING HAIR
1 - Here is the basemesh - the head we will be creating hair for.
2 - This tutorial is not about how to use Fibermesh, but for the uninitiated, simply mask out any areas which you would like to create hairs from. My personal strategy for creating hairs in large systems is to do them one small portion at a time. Here I mask off a very small area at the roots.
3 - Now use Zbrush Fibermesh to generate the fibers. These are the settings I use. Setting 1 in the below image determines the number of fibers (hairs) generated. I set this number low to avoid creating a large number of hairs at once, since we will work in small portions. Setting 2 is the profile. It is very important to use a profile of 2 or higher, because we will be doing operations on these later which will require thickness. For very thin fibers, there is no need to use more than 3 in the profile. Setting 3 determines the number of bends in each hair. For long hair, maximize this number - using too few segments will result in visible straight edges in your hair system.
4 - This is how it should look.
5 - Using the Fibermesh tools, model your hair into position.
6 - Rinse and Repeat. Continue using small segments to complete your fibermesh hair. For this hair, I have used some larger areas and larger numbers of hair underneath, closer to the skull, to fill out the hair. Then on top, I have created many smaller individual systems to give it a unique, full look.
7 - Using Fibermesh, use many single strands to create 'flyaway' hairs.
8 - When you are done creating your hairs, save out a backup file. Now combine all your hairs down into a single subtool.
You will notice that all the strands become immediately thinner, and are hardly visible in the viewport. This is because when the fibermesh subtools are combined they are converted into geometry. They have little to no thickness. Before we can use them in a render, we will have to correct this. To demonstrate how to use modeling tools to generate thickness, I will use the example of an eyelash.
PART 2 - Thickness
9 - The below picture is straight fibermesh. It has apparent thickness.
10 - And here are the lashes converted into geo (by being combined with another subtool.) Notice how thin they are.
11 - In the Zbrush tool menu, with your hair subtool selected, scroll down to the deformation submenu. In the submenu, we will give the hairs thickness by using the 'inflate' option. Very small values are needed. For these eyelashes I chose a value of .15.
12 - These are the thickened eyelashes, but we are not done yet. These lashes are uniform from the base to the tip. Real lashes (and hair) have wider roots and thinner tips.
13 - Using the inflate brush on a very low setting (1) inflate the roots of the lashes or hairs(2). Using the smooth tool, smoothing the tips of the lashes will deflate them (3). You can use the inflate brush to reduce the width of the lashes tip, but you will run the risk of negatively inflating them, so that the geo turns inside out. This is not possible using the smooth brush to reduce a hairs width.
14 - When you are done modeling, you are ready to export. Before you export, be sure to go into the tool --> polygroups option and combine the entire tool into a single polygroup. Having tools in multiple polygroups on export can cause errors when you import into other programs. There are other ways to solve this problem, this is just one solution.
Part 3 - Importing in Maya (or any other package)
16 - Import your geometry into Maya. Select the geometry. There are two things that we must do to all .OBJ files before we are ready to apply a material and render. The first thing is to go into the objects attributes editor (typically on the right side of the screen in Maya.) Here, we must turn on 'Visible in Reflections' and 'Visible in Refractions'.
17 - The second step for importing an .OBJ into Maya is to go into the 'NORMALS' Menu. With the OBJ selected, press 'unlock normals' (1), and then 'soften edge'(2). This will turn all the edgs of the hair (or any other geometry selected) into soft edges, rather than the hard edges that Maya imports.
18 - Your geometry should now look natural. Assign a shader to the material and you are ready to...
19 - ...render.
20 - Follow parts 2 and 3 to export the hair system from zbrush, and import it into Maya or another package. Your hair is ready to render. Here is the hair we created in part 1: