Houdini 20.0 Nodes Object nodes

Hair Card Generate object node

Converts dense hair curves to a polygon card, keeping the style and shape of the groom.

Since 17.0

The polygon cards output by this operator require far less memory and less computational power to render and display than dense hair curves. This makes them suitable for realtime applications.

The operator assigns groups of nearby curves to clusters and generates polygon cards for each cluster, with the width and orientation matching the original curves.


Groom Source

Loads the groom to generate hair cards for.


Groom data written to and read from files is expected to be packed and named in a specific way. Groom nodes such as Guide Groom, Guide Deform or Guide Sim write data in the expected format.

These nodes use the Guide Pack SOP to create these groom packages and Guide Unpack SOP to unpack and extract bits from them.

Source Mode

Groom Object

Load the groom from a groom object.

Groom File

Load the groom from a file.

Groom Object

Load the groom data from this source object.

Groom File

Load the groom data from this file.



Use Custom Cluster Points

Use points from the third input as cluster centers.

Number Hair Cards

The number of hair cards to generate.


The seed value used to randomly distribute cluster centers.

Curve Cluster Location

The position along the curve that is used to compute cluster centers.

0.5 means that the position half-way along the curve is used to compute clusters.


Use higher values for hair style where only the tips of hairs are visible. This distributes clusters based on tip locations, better matching the visible part of the hair.


Smooth Orientation

Averages the orientation across neighboring hair cards. Without this, the orientation can be somewhat erratic and vary wildly, which can create an undesirable look.


The number of times to apply orientation smoothing.


Width Method

The method of determining card width.

Specify Width

Manually specify a uniform width value.

Compute using Cluster Distribution

Compute card width based on the density of neighboring clusters. Sparser areas receive wider cards, such that the skin is always fully covered in cards.


Manually specified width when Width Method is set to Specify Width.

Width Scale

Scale applied on top of the computed width when Width Method is set to Compute using Cluster Distribution.

Width Max

Card width is clamped to this maximum when Width Method is set to Compute using Cluster Distribution. This prevents very sparse areas from generating extremely wide cards.


The number of polygons along the width of each card.

Bend Range

The amount by which the center of hair cards is bent outwards. This is a range of values, from which a value is picked at random for each card.

Width Ramp

Controls how cards taper towards the tip.


Extra Length

Extend the length of cards by this amount.

Division Method

The method used to determine the number of polygons along the length of each card.

Uniform Segment Count

Manually set a segment count that is used for all cards.

Segment Length

Use the number of segments necessary to match the given segment length as closely as possible.


Use the refine SOP to create the number of polygons required to accurately represent the curvature of each card.

Uniform Divisions

The number of divisions to use when Division Method is set to Uniform Segment Count.

Segment Length

The segment length to aim for when Division Method is set to Segment Length.


The refinement threshold to use when Division Method is set to Refine.

UV Generation

Generate UVs

Generate UV Coordinates for cards.

UV Method

Regular Layout

Lays out each card individually with scaling matching the world space scaling. Allows each hair card to be textured individually.

UV Reference Texture

Supply a texture with white rectangles representing hair texture strips.

The UVs of each card will be assigned to the rectangular area that most closely matches the card’s shape.

Reference Texture

The reference texture image to use with the UV Reference Texture method.

Trace Channel

The image channel in which the rectangular shapes are stored.

Packing Method

Single Tile

Fit all cards into a single tile.

Fixed Scale

Scale UV tiles by this fixed scale relative to world-space and distribute across however many tiles are required to fit all cards.


Number of pixels to pad UV islands with. Creates extra space around tiles.

See also

Object nodes

  • Agent Cam

    Create and attach camera to a crowd agent.

  • Alembic Archive

    Loads the objects from an Alembic scene archive (.abc) file into the object level.

  • Alembic Xform

    Loads only the transform from an object or objects in an Alembic scene archive (.abc).

  • Ambient Light

    Adds a constant level of light to every surface in the scene (or in the light’s mask), coming from no specific direction.

  • Auto Bone Chain Interface

    The Auto Bone Chain Interface is created by the IK from Objects and IK from Bones tools on the Rigging shelf.

  • Blend

    Switches or blends between the transformations of several input objects.

  • Blend Sticky

    Computes its transform by blending between the transforms of two or more sticky objects, allowing you to blend a position across a polygonal surface.

  • Bone

    The Bone Object is used to create hierarchies of limb-like objects that form part of a hierarchy …

  • Camera

    You can view your scene through a camera, and render from its point of view.

  • Common object parameters

  • Dop Network

    The DOP Network Object contains a dynamic simulation.

  • Environment Light

    Environment Lights provide background illumination from outside the scene.

  • Extract Transform

    The Extract Transform Object gets its transform by comparing the points of two pieces of geometry.

  • Fetch

    The Fetch Object gets its transform by copying the transform of another object.

  • Formation Crowd Example

    Crowd example showing a changing formation setup

  • Fuzzy Logic Obstacle Avoidance Example

  • Fuzzy Logic State Transition Example

  • Geometry

    Container for the geometry operators (SOPs) that define a modeled object.

  • Groom Merge

    Merges groom data from multiple objects into one.

  • Guide Deform

    Moves the curves of a groom with animated skin.

  • Guide Groom

    Generates guide curves from a skin geometry and does further processing on these using an editable SOP network contained within the node.

  • Guide Simulate

    Runs a physics simulation on the input guides.

  • Hair Card Generate

    Converts dense hair curves to a polygon card, keeping the style and shape of the groom.

  • Hair Card Texture Example

    An example of how to create a texture for hair cards.

  • Hair Generate

    Generates hair from a skin geometry and guide curves.

  • Handle

    The Handle Object is an IK tool for manipulating bones.

  • Indirect Light

    Indirect lights produce illumination that has reflected from other objects in the scene.

  • Instance

    Instance Objects can instance other geometry, light, or even subnetworks of objects.

  • LOP Import

    Imports transform data from a USD primitive in a LOP node.

  • LOP Import Camera

    Imports a USD camera primitive from a LOP node.

  • Labs Fire Presets

    Quickly generate and render fire simulations using presets for size varying from torch to small to 1m high and low

  • Light

    Light Objects cast light on other objects in a scene.

  • Light template

    A very limited light object without any built-in render properties. Use this only if you want to build completely custom light with your choice of properties.

  • Microphone

    The Microphone object specifies a listening point for the SpatialAudio CHOP.

  • Mocap Acclaim

    Import Acclaim motion capture.

  • Mocap Biped 1

    A male character with motion captured animations.

  • Mocap Biped 2

    A male character with motion captured animations.

  • Mocap Biped 3

    A male character with motion captured animations.

  • Null

    Serves as a place-holder in the scene, usually for parenting. this object does not render.

  • Path

    The Path object creates an oriented curve (path)

  • PathCV

    The PathCV object creates control vertices used by the Path object.

  • Python Script

    The Python Script object is a container for the geometry operators (SOPs) that define a modeled object.

  • Ragdoll Run Example

    Crowd example showing a simple ragdoll setup.

  • Reference Image

    Container for the Compositing operators (COP2) that define a picture.

  • Rivet

    Creates a rivet on an objects surface, usually for parenting.

  • Simple Biped

    A simple and efficient animation rig with full controls.

  • Simple Female

    A simple and efficient female character animation rig with full controls.

  • Simple Male

    A simple and efficient male character animation rig with full controls.

  • Sound

    The Sound object defines a sound emission point for the Spatial Audio chop.

  • Stadium Crowds Example

    Crowd example showing a stadium setup

  • Stereo Camera Rig

    Provides parameters to manipulate the interaxial lens distance as well as the zero parallax setting plane in the scene.

  • Stereo Camera Template

    Serves as a basis for constructing a more functional stereo camera rig as a digital asset.

  • Sticky

    Creates a sticky object based on the UV’s of a surface, usually for parenting.

  • Street Crowd Example

    Crowd example showing a street setup with two agent groups

  • Subnet

    Container for objects.

  • Switcher

    Acts as a camera but switches between the views from other cameras.

  • TOP Network

    The TOP Network operator contains object-level nodes for running tasks.

  • VR Camera

    Camera supporting VR image rendering.

  • Viewport Isolator

    A Python Script HDA providing per viewport isolation controls from selection.

  • glTF