= Dynamics with fur =

NOTE:
    This tutorial is a detailed look into what goes on at the network level. An automatic way to create the same effect is to use the [Add Dynamics|/shelf/furdynamics] tool on the shelf.

In most cases, you will want to use dynamics to allow your fur to move naturally on a character. Rarely will individual strands of hair move rigidly with a character. Applying dynamics allows them to move naturally based on the surrounding forces.

This tutorial is a continuation of [Using guide hairs|usingguides]; however, instead of using a [grid|Node:sop/grid] object we are using a [torus|Node:sop/torus] because it better illustrates how fur works with dynamics. 

    [Image:/images/fur/dynamic_nodes1.png]

# Select the [Icon:SOP/copy][copy|Node:sop/copy] node in the [network editor|/ref/panes/network] and turn on the [display flag|/nodes/sop].

# Click `obj` in the path at the top of the network editor to return to the object level, and select the guides in the viewport

    [Image:/images/fur/dynamic_wire.png]

# Once you have the guides selected, click the [Icon:DOP/wireobject][Wire Object|/shelf/wireobject] button on the __Wires__ shelf.

    This will create an `AutoDopNetwork` at the object level, as well as all of the attributes and groups needed for dynamics to work properly with fur at the geometry level.
    
# Double-click the `Fur` node to go into its geometry network, and rewire the newly created nodes into your `GUIDE_OUT` [null|Node:sop/null] node.

    [Image:/images/fur/dynamic_nodes2.png]

    TIP:
        To improve how the fur moves, increase the __Points__ on the [line|Node:sop/line] node.
    
# Click `obj` in the path at the top of the network editor to return to the object level, and double-click the `AutoDopNetwork` node to go into the dynamics network.

# Select the guides in the viewport, and click the [Icon:DOP/wireglueconstraint][Wire Glue Constraint|Node:dop/wireglueconstraint] button on the __Wires__ tab.

# In the [parameter editor|/ref/panes/parms], turn on the __Constrain To Animation__ checkbox. Turning this checkbox on makes the fur to move with the object.

    TIP:
        On the __Guide Options__ tab, you can decrease the __Radius__ to make the constraints smaller. In this example we used `0.05`.
        
    [Image:/images/fur/dynamic_const_big.png]
    [Image:/images/fur/dynamic_const_small.png]
    
# In the [parameter editor|/ref/panes/parms] of the [wire object|/shelf/wireobject], click the __Force Model__ tab and decrease the __Angular Spring Constant__ and __Angular Dampening Constant__. By default these values are very rigid for fur. 

    Try `0.025` for __Angular Spring Constant__ and `0` for __Angular Dampening Constant__.
    
# You can now apply forces to the fur such as a [Icon:DOP/fan][Fan|Node:dop/fan] or [Icon:DOP/windforce][Wind|Node:dop/fan].

    NOTE:
        Gravity is added by default when the `AutoDopNetwork` is created.

    For example:
    
    # Select the guides in the viewport, and click the [Icon:DOP/fan][Fan Force|Node:dop/fan] button on the __Drive Simulation__ shelf.
    
    # Drag the fan in the viewport using the handles and position it to blow the fur. 
    
    # Click the [Icon:PLAYBAR/play_forward] Play button to see the force applied to the fur.

    [Image:/images/fur/dynamic_fan.png]