.. _hair-dynamics:

*************
Hair Dynamics
*************

.. admonition:: Reference
   :class: refbox

   :Panel:     :menuselection:`Particle System --> Hair Dynamics`

Hair particles can have dynamic properties using physics.
To enable hair physics, click the checkbox beside *Hair Dynamics*.

Quality Steps
   Quality of the simulation in steps per frame (higher is better quality but slower).

Pin Goal Strength
   Spring stiffness of the vertex target position.

.. warning::

   If you use motion blur in your animation,
   you will need to bake one extra frame past the last frame which you will be rendering.


Structure
=========

.. admonition:: Reference
   :class: refbox

   :Panel:     :menuselection:`Particle System --> Hair Dynamics --> Structure`

Mass
   Value for the mass of the hair.
Stiffness
   Controls the bending stiffness of the hair strands.

   Random
      Random stiffness of hair.

Damping
   Damping of bending motion.


Volume
======

.. admonition:: Reference
   :class: refbox

   :Panel:     :menuselection:`Particle System --> Hair Dynamics --> Volume`

Some phenomena of real-world hair can be simulated more efficiently using a volumetric model instead
of the basic geometric strand model. This means constructing a regular grid such as those used in
fluid simulations and interpolating hair properties between the grid cells.

Air Drag
   Controls how thick the air is around the hair causing the hair to flow slower.
Internal Friction
   Amount of friction between individual hairs.
Voxel Grid Cell Size
   Size of the voxel grid cells for interaction effects.

Density Target
   Maximum density if the hair.
Density Strength
   The influence that the *Density Target* has on the simulation.