Houdini 20.0 Nodes Object nodes

TOP Network object node

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

Since 17.5


Cook Controls

Generate Static Work Items

Generates static work items in all nodes in the TOP network. None of the work items will be cooked, and dynamic nodes will do nothing.

Cook Output Node

Cooks the output node in the TOP network and any out-of-date nodes connected to it. If you want to recook all the nodes in the TOP network, click Dirty all first and then click this button.

Dirty All

Dirties all the work items in all of the TOP nodes inside the network and marks every node inside the network as needing to recook.

Cancel Cook

If any nodes in the TOP network are currently cooking, cancels their cook.


You can add cook controls for any TOP network to any node. For more information, see Adding TOP network cook controls to any node.

Save/Load Task Graph

Save Task Graph

Saves the state of all work items in the TOP network to an external file, which you can then restore with the Load Task Graph button. The task graph is saved to the path specified by the Task Graph File parameter.

Load Task Graph

Dirties the TOP network and loads the task graph file specified by the Task Graph File parameter.

Task Graph File

Specifies the path to the task graph cache file to save/load. This is used by Save Task Graph and Load Task Graph buttons, and it is where the network auto saves to when Auto-Save Rate is turned on.

Auto-Save Rate

When on, TOPs saves the task graph to disk at regular intervals. The save rate is specified in seconds. For example, the default rate of 10 saves the graph every 10 seconds. This can be useful when you want to checkpoint a large graph in its fully-cooked state.

Save Graph Attributes to .hip

When on, all the global attributes stored on the graph are saved to its .hip file. This makes it so that when you next open the .hip, the global attributes will still be available on the graph.

Work Items and Scheduling

Default TOP Scheduler

Specifies the default scheduler node that is used by all TOP nodes in the network, unless a TOP node has its own Scheduler override.

This can be a relative node path. As such, since your Schedulers are most likely at the main level of the network (and not inside a subnet), you can just use the Scheduler’s node name. For example, localscheduler or hqueuescheduler.

Default Item Label

When on, specifies the label that is assigned to any work item in the TOP network that was generated by a Processor with the Use Default Label setting.

On Node Recook

Determines what happens to work items when a node is recooked after it has been modified. By default, PDG will regenerate work items in the node, which updates their attribute values to match the parameters and invalidates existing output caches.

Update Work Items and Invalidate Caches

The default behavior. When a TOP node recooks, its work items are updated to match the parameters on the node. Work items that are modified in the process then have their output files invalidated.

Update Work Items Only

Attributes on work items are updated to match the parameters on the node, but the output cache files are not invalidated.

Ignore Changes

Nodes are not automatically recooked. Work items are left as-is unless the node is explicitly dirtied.

Evaluation Time

Determines what time value is used when evaluating parameters in the TOP network without an active work item. If a parameter is evaluated against a particular work item, the work item’s frame will determine the parameter’s evaluation time.

Network Cook Time

Parameters are evaluated using the time value that was set when the TOP network first began to cook. Changes to the current time while the network is cooking will not affect parameter evaluation.

Global Start Time

Parameters are evaluated using the global start frame/time value, regardless of the current evaluation time.


Parameters are evaluated at the custom time value specified by the Custom Time parameter.

Custom Time

Specifies the time value to use when evaluating parameters in the TOP network without an active work item.

This parameter is only available when Evaluation Time is set to Custom.

Save Scene File if Required

When this parameter is enabled, PDG will save the current .hip file before cooking if there are unsaved changes and work items in the graph use the scene file. Otherwise, if this parameter is disabled, the scene file will never be saved automatically.

A dialog will be displayed before the scene is saved, however the dialog also an option to make the selection the default use it for future cooks.

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