When you first create hair it appears sticking out normal to the surface. For a more natural look, play the hair simulation to see the hair react to gravity and then you can set a more realistic Start position for the hair. In these steps you create hair on a NURBS model and set a Start position after playing the simulation. You use Interactive Playback to play the simulation while adjusting dynamic hair system attributes and see how your changes affect the simulation.

To create hair on a model

1. Select Marion’s scalp, as shown in the image below.

   

2. Select Hair > Create Hair > and in the Create Hair Options window, specify the following:
   • Set Output to Paint Effects.
   • Ensure that Create Rest Curves is turned off.
   • Ensure that Grid is turned on and set the U count to 26 and the V count to 22. These determine how many hair curves within each UV range.
   • Set the Passive fill to 0. No passive curves will be used in this lesson. The behavior of passive curves is interpolated between neighboring active curves. For more information, see Passive hair curves in the Hair guide.
   • Set the Randomization to 0.5. A value of 1 represents total randomization of placement of hair curves on the surface, whereas a value of 0 represents no randomization.
   • Ensure that Edge Bounded is turned off.
   • Turn the Equalize option on. This ensures the hair curves are evenly distributed over the surface.
   • Ensure that Dynamic is turned on.
   • Set the Points per hair to 10. This sets the number of segments per hair. More segments are needed to make long hair look natural or to create complex short hairstyles. As you increase the number of segments, you decrease the performance (speed) of the simulation.
   • Set the Length to 10. This value is relative to the world space units.
   • Click Create Hairs.

   The hair is attached to the scalp and sticks out perpendicular to the surface. You are looking at the Current Position of the hair, which is also referred to as the “dynamic” position. Do not edit the hair curves in this view; edit only in Start Position or Rest Position.

   

To play the hair simulation

1. Click the Play button to play the simulation.

   The hair falls due to default dynamic forces, such as gravity, which are found in the hair system attributes. However the hair takes a while to fall, which is as a result of a high Display Quality setting.

2. Click the Stop button to stop the simulation when the hair is relaxed as it is in the following image.

   

   Notice the hairs are quite stiff and stick out from the scalp instead of naturally falling closer to the scalp. To make the hair appear less stiff you can either increase the number of Points Per Hair (segments), which increases the simulation and render time, or you can reduce the Stiffness value in the hair system’s Dynamic attributes.

   In the next part of the lesson you adjust dynamic settings of the hair system, including Stiffness and Gravity, to achieve more naturally behaving hair.

To improve playback performance and modify dynamic settings

1. In the Attribute Editor ( + a) select the hairSystemShape1 tab and change Display Quality to 2. This affects how many hairs display in the scene view, but has no effect on how much hair appears in the software render. By reducing the Display Quality, this speeds up the playback of the hair simulation.
2. In the Dynamics section the default value for Stiffness is 0.10. Since the hair is quite stiff, reduce the Stiffness value to 0.07.
3. Select Solvers > Interactive Playback to play the simulation. Watch the hair begin to relax more.
4. With the simulation still playing go to the Dynamics section of the hairSystemShape1 tab and change the Gravity value to 2.5. Watch the hair relax even more and rest closer to the scalp, as hair does naturally.
5. Click the Stop button when the hair has relaxed as in the following image.

   

To set the position of the hair for the start frame

1. When you are playing the hair simulation, by default you are viewing the Current position curves. To select all the Current position curves, click any hair curve and then select Hair > Convert Selection > To Current Positions.
2. To set the start frame of the hair simulation to how the hair appears now, select Hair > Set Start Position > From Current.
3. Select Hair > Display > Start Position to view the Start curves and see that they took on the Current Position.
4. Click the button to rewind to the start frame.

   The position of the hair at the start frame is now relaxed.