Command entry:Select an object with the Hair And Fur modifier applied.
Modify panel
Dynamics rollout
For hair to seem natural in an animation, it must respond to the motion of the body it's attached to and to external influences
such as wind and gravity. Hair's Dynamics functions let the hair behave like real-world hair, in interactive (Live) or Precomputed
mode.
Designating Collision Surfaces
Hair dynamics uses guide hairs to calculate collision. To reduce computation, you have to explicitly designate the objects
with which hair will collide. The object from which the hair grows is a special case: to have hair collide with this object
(for example, a human head), simply turn on Use Growth Object.
If you want more than one Hair modifier to interact with a particular collision object, you have to add that object as a collision
object for each different Hair And Fur modifier.
The modifier provides two different methods for calculating collision: Sphere and Polygon. Spherical collision uses a bounding
sphere for collision objects; polygonal collision uses the collision object's actual geometry. The Polygon option is more
accurate, but the Sphere option is quicker to calculate.
Procedures
Example: To view hair dynamics in real time:
- Apply the Hair And Fur modifier to an object.
- On the Dynamics rollout (scroll the command panel to view it), set Mode to Live.
- Move the object around.
The hair moves realistically.
- On the Tools rollout, click Regrow Hair.
The hair resumes its default position, growing straight out of the object.
- Click (Play Animation).
- The hair settles and droops, as if affected by gravity. Note that, as the animation repeats, the effects of gravity are cumulative;
the hair animation doesn't restart at the first frame.
- On the Tools rollout, click Regrow Hair again.
- Add a Wind space warp to the scene.
- On the Dynamics rollout, set Dynamics Params Gravity to 0.0.
- In the External Forces group (at the bottom of the Dynamics rollout), click Add and then select the Wind space warp.
- Play the animation again.
This time, the hair isn't affected by gravity, but simply blown by the wind. Again, the effect is cumulative and the animation
doesn't repeat.
All of this animation takes place only in real time; no keyframes are set, so it can't be rendered. To learn how to set up
a renderable dynamics simulation with Hair, see the following procedure.
To generate a precomputed dynamics simulation with Hair:
- Apply the Hair And Fur modifier to an object.
- Set up the animation. It could simply be motion of the growth object, or you could use the Dynamics rollout External Forces group to add space warps, such as Wind, that should affect the hair. Actually, because the hair is affected
by its own gravity by default, you don't need to set up any explicit animation at all to see hair dynamics.
- On the Modify panel Dynamics rollout, use the Collisions group to set objects the hair should collide with. Also set other simulation parameters
in the Dynamics Params group.
- In the Stat Files group, click the ellipsis (...) button. Use the Save As dialog to specify the location and name of the stat
files to be generated.
NoteWhen you run the simulation, Hair will generate a separate stat file for each animation frame.
ImportantIf you plan to render the animation with a networked render farm, make sure the path you specify can be seen in exactly the
same way from each node on the render farm. If stat files aren’t found, hair will be stiff and just oriented to the skin as
it moves. If the wrong stat files are found, hair can float right off an object.
TipIf using Windows XP, click the My Network Places button to set a path using the Universal Naming Convention (UNC), even if
it's on a local drive. Such a path can be accessed readily by other computers on the network.
The path and stat file name appear in the text field next to the ellipsis button.
- In the Simulation group, set the frame range for the simulation and then click Run.
Hair runs the dynamics simulation and generates a stat file for each frame in the animation. It also automatically sets the
mode to Precomputed, so when you play or render the animation, it reads the stat files and uses the information for the hair
positioning in each frame.
- Play the animation.
The dynamics simulation stored in the stat files appears in the viewports.
- In the Mode group, choose None, and then play the animation again.
The dynamics animation no longer appears. However, it's still stored in the stat files, and will reappear if you choose Precomputed.
- Make sure Precomputed is on, and then render the animation.
Interface
Mode group
Chooses the method Hair uses to generate dynamics. Live mode is suitable for experimentation, but for best results when rendering
animation with Hair, use Precomputed mode.
- Hair doesn't simulate dynamics.
- Hair simulates dynamics interactively in the viewports, but doesn't generate animation keyframes or stat files for the dynamics.
For best results with Live mode, turn off Display rollout Display Hairs group As Geometry.
For some methods of using live dynamics, see this procedure: Example: To view hair dynamics in real time:.
If you press ESC while using live dynamics, 3ds Max displays a dialog that asks whether you want to stop live dynamics. Both Freeze and Stop reset the mode to None, but Freeze
freezes the hair in its current position. You can use this as a starting point for precomputed dynamics, or as a point from
which you style the hair.
- Lets you generate stat files for rendering dynamics-animated hair. Available only after setting a name and location for stat
files (see following and To generate a precomputed dynamics simulation with Hair:).
Stat Files group
Stat files let you record and play back a Hair-generated dynamics simulation. For a workflow example, see this procedure:
To generate a precomputed dynamics simulation with Hair:.
- Text field
-
Displays the path and file name for the stat files.
- (ellipsis button)
-
Click to choose a name prefix and location for stat files using the Save As dialog.
Hair adds a four-digit frame number (with leading zeroes) and the file name extension “.stat” to the name you provide (for example, hair_test0001.stat).
- Delete all files
-
Deletes stat files from the target directory. The files must have the name prefix you assigned using the ... button.
Now, when you play or render the animation, Hair uses the stat files as originally generated.
Simulation group
Determines the extent of the simulation, and lets you run it. These controls become available only after you choose Precomputed
mode and specify stat files in the Stat Files group. Set Start and End to the frames at which to begin and end the simulation,
and then click the Run button. 3ds Max then computes the dynamics and saves the stat files.
- Start
-
The first frame to consider in calculating the simulation.
- End
-
The final frame to consider in calculating the simulation.
- Run
-
Click to run the simulation and generate the stat files within the frame range indicated by Start and End.
To abort a simulation while it's running, click Cancel on the status bar.
Dynamics Params group
These controls specify the basic parameters for the dynamics simulation. The Stiffness, Root Hold, and Dampen values can be
mapped: click the map button to the right of the spinner to assign a map. Grayscale values in the map multiply the parameter's
value at that hair location.
- Gravity
-
Lets you specify a force that moves hair vertically in world space. Negative values pull hair up while positive values pull
it down. To cause hair not to be affected by gravity, set the value to 0.0. Default=1.0. Range=–999.0 to 999.0.
- Stiffness
-
Controls the magnitude of the effect of dynamics. If you set Stiffness to 1.0, the dynamics will have no effect. Default=0.4.
Range=0.0 to 1.0.
- Root Hold
-
Comparable to stiffness, but affects the hair only at the roots. Default=1.0. Range=0.0 to 1.0.
- Dampen
-
Dynamic hair carries velocity forward to the next frame. Increasing dampening increases the amount by which these velocities
are diminished. Thus, a higher Dampen value means that hair dynamics will be less active (the hair can also start to get “floaty”).
Default=0.0. Range=0.0 to 1.0.
Collisions group
Use these settings to determine which objects hair collides with during a dynamic simulation and the method by which collision
is calculated.
- Collisions are not considered during the dynamic simulation. This can cause the hair to penetrate its growth object as well
as other objects it comes into contact with.
- Hair uses a spherical bounding box to calculate collisions. This method is faster because it requires less computation, but
can cause inaccurate results. It's most effective when the hair is seen from a distance.
- Hair considers each polygon in the collision objects. This is the slowest method, but the most accurate.
- Use Growth Object
-
When on, hair collides with the growth (mesh) object.
- Objects list
-
Lists the names of scene objects with which hair should collide.
- Add
-
To add an object to the list, click Add and then click the object in a viewport.
- Replace
-
To replace an object, highlight its name in the list, click Replace, then click a different object in a viewport.
- Delete
-
To remove an object, highlight its name in the list, then click Delete.
External Forces group
This group lets you specify space warps that will affect the hair during the dynamics simulation. For example, you can add a Wind space warp to cause the hair to be blown by a breeze.
NoteHair dynamics already has a built-in gravity force, so it's not necessary to add one.
- Objects list
-
Lists the names of forces that dynamically affect the hair.
- Add
-
To add a space warp to the list, click Add and then click the warp's icon in a viewport.
- Replace
-
To replace a space warp, highlight its name in the list, click Replace, then click a different warp's icon in a viewport.
- Delete
-
To remove a space warp, highlight its name in the list, then click Delete.