.. index:: Geometry Nodes; Clump Hair Curves

*****************
Clump Hair Curves
*****************

The *Clump Hair Curves* node gathers nearby hair curves together around designated guide curves,
creating clump formations commonly seen in real hair, fur, and grass.
It is a key step in grooming workflows for adding realism and structure by simulating
how strands naturally group due to moisture, product, or physical interaction.

.. peertube:: gnhg72C8JoNYmNy441QHgt


Inputs
======

Geometry
   The input geometry containing the hair curves to be clumped.

Factor
   Controls the overall strength of the clumping effect.
   A value of 0.0 applies no clumping, while 1.0 fully pulls curves toward their guides.

Shape
   Defines how the clumping influence changes along the length of each curve.
   A value of 0.0 applies a constant strength, while 0.5 results in a linear falloff from root to tip.

Tip Spread
   Adds random variation to the positions of curve tips,
   preventing perfect convergence and helping clumps look more natural.

Clump Offset
   Applies a random directional offset to entire clumps, introducing subtle variation between groups.

Distance Falloff
   Defines how the influence of each guide curve decreases with distance.
   A value of 0.0 disables distance-based falloff, making all nearby curves equally affected.

Distance Threshold
   Sets the maximum distance from a guide at which clumping has an effect.
   Curves farther than this threshold will not be influenced by that guide.

Seed
   Controls the randomization used for offsets and variation.
   Changing this value alters the random distribution of clumping while keeping the same parameters.

Preserve Length
   When enabled, maintains the original length of each curve during deformation.
   When disabled, curves may stretch or shrink slightly as they are pulled toward guides.


Guide Map
---------

Guide Index
   A map that specifies which guide curve acts as the center for each clump.
   If provided, this takes priority over any existing ``guide_curve_index`` attribute,
   and the *Guide Distance* and *Guide Mask* inputs are ignored.

Guide Distance
   The minimum distance between selected guide curves when generating a new guide map.
   Larger values produce fewer, larger clumps.

Guide Mask
   Defines which curves can be used as guides during automatic guide map creation.

Existing Guide Map
   When enabled, uses the existing guide map attribute if it is already available.
   If disabled and *Guide Index* is not provided, a new
   :doc:`guide map </modeling/geometry_nodes/hair/guides/create_guide_index_map>`
   is generated using *Guide Distance* and *Guide Mask*.
   Creating the guide map separately allows for finer control over guide placement and grouping.


Outputs
=======

Geometry
   The resulting geometry with clumped hair curves.


Guide Map
---------

Guide Index
   The guide index map used for this operation.
   If a new guide map was generated by this node, it is stored and provided through this output
   for reuse in subsequent operations.
