Houdini 20.0 Nodes LOP nodes

Component Output

Assembles the final Component prim, in a network created by the Component Builder tool.

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Since 19.0


This node is part of the network created by the Component Builder tool. The component builder network gives you a framework in LOPs to create a Component model (usually a prop, such as a chair or tree) and export it to USD for re-use.

This node takes the “temp” prims created by the other nodes in the component network, and assembles them into a stage with the Component model in a root prim, ready to be exported into a proper component layer USD file.

You can dive inside this node, to a LOP network inside. In this network you can use LOP nodes to add an additional layer on top of the fully constructed component model. For example, you could add a layer with lights, which would then travel with the asset.

See how to use the component builder tool for more information.


Component Options


Indicates the source type connected to the node. Most of the time 'Component Geometry' is the right choice, as it expects other Component Builder nodes as inputs. 'Input Primitives' reads the input primitives as-is. 'Scene Import' will read the geometry and materials of a component from the Scene Import LOP.

Root Prim

The root prim of the component asset, which is generally the same as the name. Used when not detected from the input nodes.


The root prim of the component asset, which is generally the same as the name. Used when not detected from the input nodes.

Set Default Variants

Set Default Variants

Sets the default geometry and material variant selections for the component.


When Set default variants is on, the name of the default geometry variant. (The name of each geometry variant is set on the corresponding Component Geometry node using the Advanced ▸ Geo Variant Name parameter. The default uses the name of the node as the variant name.)


When Set default variants is on, the name of the default geometry variant. (The name of each material variant is set on the corresponding Component Material node using the Variant Name parameter. The default is the name of the node.)


Setup Class for Inherits

Adds an inherits arc from the Component prim a class prim, so this component may receive shot- and sequence-specific overrides.

Set Variants Inside (Extra Layer)

Lets you override the variant selections using Lop nodes inside of this node. This lets you create variant sets that control both the 'geo' and 'mtl' variants. A consequence of this, is your geometry is likely to disappear from the viewport and scene graph tree, until you choose Default Variants on this node, or select variants inside of the Componen Output manually.

One use case for this is an “uber” variant, that controls both the geo and mtl variant selections at the same time. Such a variant cannot work if the layers already have variant selections, because the existing variant selection opinions are equally as strong.

Asset Identifier

Optional metadata describing where this component lives on-disk.

Asset Name

Optional metadata describing the name of this component lives.

Asset Version

Optional version string.

Asset Dependencies

Optional string listing arbitrary dependencies.

Houdini Icon

Optional path to an icon file, or Houdini icon name (for example, SHELF_tree_conifer). If you set this, Houdini’s Scene Graph Tree pane will display the component prim using this icon.

Custom Data

Use this multi-parm to add custom attributes to the main Component parm.


Load from Disk

Once you have written the file out to USD, you can turn this on to load the component output from disk rather than cooking the input network.

Save to Disk

Exports the component to disk.

Save to Disk in Background

Exports the component to disk in a background thread.


Reloads the component from disk.


Path to the component model’s asset.usda on disk. By default is derived from the component’s name.

Handle Missing Files

Controls whether missing files are errors or warnings.

Export Options

Payload Layer

The name of the file which is payloaded into the asset. It gathers the geometry, material, and extra layers. When the Source is set to __Input Primitives___ this node will gather everything into this layer and payload it. Location is relative to the 'asset.usda' defined in the Location path.

Geometry Layer

Name of the file where all the component geometry and component geometry variant output is stored. Location is relative to the 'asset.usda' defined in the Location path.

Material Layer

Name of the file where all the component materials is stored. Only applies to component materials defined below component geometry variants, if those are present to in the network. Location is relative to the 'asset.usda' defined in the Location path.

Extra Layer

Name of the file where any opinions authored within this node’s dive target are stored. Location is relative to the 'asset.usda' defined in the Location path.

Localize External Non-USD Files

Copies any non-USD files into a subdirectory of the output location, to make portable, reusable USD models. External files are copied and localized into the specified Sub-Directory.

The most common use case is to ensure texture maps for a model are all located within the asset’s output directory.


The sub-folder of the output location, where localized files will be copied.

Variant Layers

Variant Layers

When this is on, the node generates an extra USD layer file per variant, along with a thumbnail. This can make it more convenient to work with variants as separate assets, for example in the Layout node’s asset gallery, or an asset management system.

Variant Set

The name of the variant set to use when writing out separate USD files for each variant. The default variant set name for geometry variants created with the component builder network is geo (the default for this parameter). The default variant set name for material variants created with the component builder network is mtl. If you changed the default variant set name, or somehow created variants outside the component builder system, you may need to change this.

Directory Name

The name of the subdirectory (next to the main USD file) to write the variant layer files into.

Save Style

This node can apply some transformations to the layer stack before writing out files. These transformations do not affect the final composed stage, only the number of layer files generated.

Flatten Implicit Layers (Collapse Implicit Sublayers, Preserve References)

The default. Composes anonymous in-memory layers down onto the nearest layer with a file path (so the node will write out any layers that have file path metadata to separate USD files). This preserves references, variants, and other composition arcs.

Flatten All Layers (Combine All Sublayers, Preserve References)

This composes all layers (both anonymous layers and layers with file paths) into a single layer. This preserves references, variants, and other composition arcs, so the node may still write out more than one file if external files were referenced in.

Separate Layers (Preserve All Sublayers and References)

Don’t compose any layers in any way. Even anonymous in-memory layers will be saved out to their own files (you should turn off Error saving layers with implicit paths so the node doesn’t error trying to save anonymous layers).

This may be useful for debugging, especially in combination with debug flags on nodes, to see what each LOP node is doing.

When the node has to write out a layer without file path metadata, it will automatically generate a relative file path based on information such as the node path of the node that generated the layer.

Flatten Stage (Collapse All Sublayers and References)

This flattens all layers into a single stage, and “bakes in” all composition arcs, even variant selections. This discards information such as which opinions came from which layer, and unused variants. This writes out a single USD file.

This may be useful if you want to “delete history” and make it seem like it a file wasn’t composed from layers, references, variants, and so on.


If you want to “preserve history” but want the convenience and portability of a single file, use the USD Zip render node to generate a .usdz file.

Strip Layers Above Layer Breaks

Enable this option to prevent layers authored above Layer Break nodes from being written to disk by this ROP. This allows a Layer Break node to dictate which portions of the LOP Network are to be saved. Disabling this option allows this behavior to be overridden, forcing the full stage authored by the LOP network to be written to disk. This may be used for debugging purposes, or to write a complete scene to disk for rendering.

Flush Data After Each Frame

When this is on, the node writes out each frame’s data to disk before cooking the LOP Network to generate the next frame of data. When this is off (the default), the node cooks the data for all frames into memory and writes out the animated files all at once. Turning on this option ensures that only a single frame worth of data is in RAM at any one time, allowing arbitrarily large USD files to be created. But saving each frame can be slightly slower, and the generated files may be larger because of the way USD files append new data to an existing file. See saving animation above.

When this option is on, this ROP can also generate separate USD files for each frame. To do this, embed the local variable for the current frame number in the Output file path (and other layer save paths) so each frame will write out files with unique names. For example:


See expression in filenames for more information.

Layer Metadata

Error Saving Layer With No Default Primitive

When this is on, the render node will error and stop cooking if you haven’t specified a default primitive for all layers being written out.

This is a way to force yourself to make sure layers have default prims, so you know you can reference in files without having to manually specify a top-level prim.

Save ROP’s Time Information to Output

Write the start and end frames, as well as the current frames per second setting, to the top-level output file.

Clear Houdini-Specific Custom Data

LOP networks often attach Houdini-specific custom data to layers, prims, and properties. Houdini does not need this data to be stored on disk (usually it is related to how to write files), so by default Houdini strips out this data before saving. Normally there’s no reason to turn this parameter off (it’s possible it might help SideFX diagnosing a problem).

Ensure Basic Metrics are Set on All Layers

This options ensures that the upAxis and metersPerUnit metadata is set in every USD file written to disk. If a value has not been explicitly authored on a layer by the LOP Network, the default up axis and meters per unit values from the Lighting Preferences are used.

Context options

Set ROP Cook Context Options

Controls whether this node sets the @ropcook, @ropstart, @ropend, and @ropinc context options when rendering. If enabled, these context options are automatically set to 1 for @ropcook, and the values of the Start, End, and Increment Frame values from this node for @ropstart, @ropend, and @ropinc. Using these standard context options it is easier to set up predictable behavior for Cache LOPs, LOPs that create ranges of time sampled values, and LOP nodes that are only used for generating viewport previews or final rendered output.

Number of Options

Lets you specify context options that only apply while writing out files from this node. Set the number of context options to define/override, or use the plus and minus buttons to add or remove options.

You could have two separate USD render nodes with different context options, so they would write out different USD from the same LOP network depending on uses of @contextoption references in expressions. This could be useful for wedging, or to cause the LOP network to configure the stage in ways that are not good for interactively, but should be written to disk.

Option Name

For each option, the name of the option. You can reference this option in an expression using @name.

Option Type

For each option, the type of data stored in the option, either a floating point number of a string.

Option Value

For each option, the value of the option (while this node writes out USD).

Initialize Simulation OPs

Initialize DOP simulations before rendering.

Alfred Style Progress

Print percentage complete value as files are written. This is in the style expected by Pixar’s Alfred render queue.

Report Network Use

Print the number of bytes sent or received by the distributed simulation nodes during cooks triggered by this node.

This does not track network usage from, for example, saving a file to an NFS mount. It only tracks the network communication of distributed Houdini nodes.


Generate Thumbnail

Click this to manually generate the thumbnail image and save it in the component output directory (as set up in the Caching section of this node).


How the thumbnail is generated or sourced.

Houdini GL

Generates the thumbnail from the Houdini GL ROP.


Select an image on disk, which is copied to the asset’s output directory.


Select a render delegate to render your thumbnail image.


Save the current viewport as your thumbnail image.


Resolution of the generated thumbnail. Only applies to the Houdini GL or Render modes.

Camera and Scene

Source of the thumbnail camera and scene.


Generates a thumbnail camera automatically from the bounds. Includes any Thumbnail.usda files on the Houdini path, to customize lights.

Second Input

Uses a camera from the second input, to generate the thumbnail. Any other objects, such as lights, will also be used to render the thumbnail image.

Automatic Camera

View Thumbnail Camera

Turn this on to temporarily look through the thumbnail camera in the viewer, to adjust the thumbnail positioning as-needed.


Rotate the camera around the Y axis.


Raise and lower the camera.


Move the camera closer or further from the model.

Second Input


Second input camera prim used to create thumbnails.

Thumbnail Scene Quickstart

Sets up a camera and insertion point, to make custom thumbnail scenes easier to setup.

See also

LOP nodes

  • Add Variant

    Adds one or more variants to a variant set on a primitive. This node creates the primitive if it doesn’t exist.

  • Additional Render Vars

    Create multiple render vars.

  • Asset Reference

    Reference, Transform, and select variants of a USD Asset.

  • Assign Material

    Assigns a material to one or more USD primitives. You can use also programmatically assign materials using VEX, programmatically override material settings for each assignment, and programmatically assign materials to geometry subsets.

  • Assign Prototypes

    Switch point instances or USD instanceable prims to instance a different prototype.

  • Attribute VOP

    Create/edit USD attribute values using a VOP network.

  • Attribute Wrangle

    Create/edit USD primitive attributes using a VEX snippet.

  • Auto Select LOD

    Automatically selects a level-of-detail variant based on the primitive’s distance from the camera.

  • Background Plate

    Sets up hold-out or matte objects that leave holes in the scene through which the background is visible. These prims still take shadows and contribute to reflections as if they were the background.

  • Bake Skinning

    Bakes animation driven by a UsdSkel into transforms and point positions.

  • Basis Curves

    Creates or edits a basis curves shape primitive.

  • Begin Context Options Block

    This node begins a block of LOP nodes, within which certain context options have certain values.

  • Blend

    Partially applies edits to a layer’s attributes based on a fractional weight.

  • Blend Constraint

    Blends transforms according to a list of weights specified as parameters.

  • Cache

    Caches the results of cooking the network at different times, increasing playback speed.

  • Camera

    Adds a USD camera to the scene.

  • Capsule

    Creates or edits a capsule (tube with hemispherical ends) shape primitive.

  • Collection

    Creates/edits collections using primitive patterns.

  • Component Geometry

    Geometry container or import source, in a network created by the Component Builder tool.

  • Component Geometry Variants

    Sets up geometry variants, in a network created by the Component Builder tool.

  • Component Material

    Assigns materials to geometry in a network created by the Component Builder tool.

  • Component Output

    Assembles the final Component prim, in a network created by the Component Builder tool.

  • Cone

    Creates or edits a cone shape primitive.

  • Configure Layer

    Edits metadata on a layer.

  • Configure Primitives

    Edits various metadata on one or more primitives.

  • Configure Properties

    Configures metadata on properties (relationships and attributes).

  • Configure Stage

    Configures metadata for how to load layers into the stage and asset resolution.

  • Coordinate System

    Define named coordinate systems used in shaders.

  • Copy Property

    Copy properties from one primitive to another, or renames properties on a primitive.

  • Create LOD

    Uses the PolyReduce SOP to automatically generate multiple levels of detail from a high-res model, and stores them as USD variants.

  • Cube

    Creates or edits a cube shape primitive.

  • Cylinder

    Creates or edits a cylinder shape primitive.

  • Distant Light

    Creates or edits a USD Distant Light, representing a far-off light source such as the sun. Adds some useful Karma-specific attributes.

  • Dome Light

    Creates or edits a USD Dome Light prim. A dome light emits light inward, simulating light coming from the sky/environment surrounding the scene.

  • Drop

    Runs a simulation to drop primitives under gravity.

  • Duplicate

    Creates copies of a prim (and its descendants).

  • Edit

    Interactively transforms prims in the viewer. Can use physics collisions to position props realistically.

  • Edit Context Options

  • Edit Material

    Allows you to edit an existing USD material by modifying parameters and shader connections. This can be useful if the existing material is on a non-editable layer.

  • Edit Material Properties

    Lets you build a spare parameter interface that reflects material or shader input attributes to directly edit their values.

  • Edit Properties

    Lets you build a spare parameter interface to directly edit attribute and relationship values.

  • Edit Properties

    Lets you refer to the parameter on another node to directly edit attribute and relationship values.

  • Edit Prototypes

    Modify the prototypes of native or point instances in-place, without disturbing the instancing setup.

  • Edit Target Layer

    Allows you to apply edits directly in a lower layer, instead of overriding prims and attributes in the active layer.

  • Error

    Generates a message, warning, or error, which can show up on a parent asset.

  • Explore Variants

    Visualize, set, or extract variants on primitives.

  • Extract Instances

    Converts (heroes) an instance into a real editable prim.

  • Fetch

    Grabs the output of another LOP, potentially in another LOP network.

  • File Cache

    Caches (writes out once and then reads from) USD layers (possibly animated) to disk.

  • Follow Path Constraint

    Constrains a prim to follow a path curve.

  • For Each

    The end node of a For-Each loop block.

  • Geometry Clip Sequence

  • Geometry Sequence

    Imports a sequence of geometry files into LOPs as animated geometry.

  • Geometry Subset VOP

    Creates USD geometry subsets within geometry prims (similar to groups in SOPs) based on evaluating a VEXpression or VOP network.

  • Graft Branches

    Takes prims/branches from the second input and attaches them onto branches of the scene graph tree in the first input.

  • Graft Stages

    Takes scene graph trees from other inputs and attaches them onto branches of the scene graph tree in the first input.

  • HDA Dynamic Payload

    Cooks a OBJ or SOP asset on disk and imports the animated geometry output as a USD payload.

  • Hermite Curves

    Creates or edits a hermite curves shape primitive.

  • Houdini Feather Procedural

    Generates feathers for rendering.

  • Houdini Preview Procedurals

    Invokes Houdini Procedurals while working interactively.

  • Houdini Procedural: Hair

    Houdini Hair Procedural for Solaris.

  • Houdini Procedural: Ocean

    Houdini Ocean Procedural for Solaris.

  • Inline USD

    Parses usda code representing a layer and adds it to the layer stack.

  • Insertion Point

    Represents a point in the node graph where nodes can be inserted.

  • Instancer

    Instances or copies primitives onto points.

  • Instancer

    Create multiple render products sharing common settings.

  • Isolate Scene

    Work in masked areas of the stage.

  • Karma

    Renders the USD scene using Houdini’s Karma renderer.

  • Karma Cryptomatte

    Setup Cryptomatte AOVs for Karma.

  • Karma Fog Box

    Creates a constant volume within a box.

  • Karma Physical Sky

    Creates a Karma Sky Dome and Sun Light rig.

  • Karma Render Properties

    Configure Render Properties for Karma.

  • Karma Sky Dome Light

    Creates or edits a Karma Sky Dome Light.

  • Karma Standard Render Vars

    Create standard karma render vars (AOVs/Image Planes).

  • LPE Tag

    Manage Lights' LPE Tags.

  • Labs RizomUV Optimize

  • Labs RizomUV Rectangularize

  • Labs RizomUV Unwrap

  • Layer Break

    Starts a new active sublayer that subsequent nodes will edit, and indicates all previous layers will be discarded when saving to disk.

  • Layer Replace

    Replaces all uses of a certain layer with a substitute layer from its second input.

  • Layout

    Provides tools for populating a scene with instanced USD assets. You can place individual components, paint/scatter components in different ways using customizable brushes, and edit existing instances.

  • Light

    Creates or edits a USD Light prim. This node also adds some useful Karma-specific attributes.

  • Light Filter Library

    Authors USD light filter primitives from VOP nodes.

  • Light Linker

    Creates USD light link properties based on rules.

  • Light Mixer

    Lets you interactively edit USD properties for multiple lights.

  • Load Layer for Editing

  • Loft Payload Info

    Adds basic information from inside a payload to the primitive that loads the payload.

  • Look At Constraint

    Constrains a prim to always point toward a target.

  • Mask from Bounds

    Sets a primvar based on whether/by how much selected prims are inside a bounding shape.

  • Match Size

    Resizes and recenters the input geometry to match a reference bounding box.

  • Material Library

    Authors USD material primitives from shader VOP nodes.

  • Material Linker

    Creates material assignments based on rules.

  • Material Variation

    Creates attributes/primvars to override material parameters per-prim/instance.

  • Merge LOP

    Merges the layers from incoming stages into a unified layer stack.

  • Merge Point Instancers

    Merges point instancers into a single consolidated point instancer.

  • Mesh

    Creates or edits a mesh shape primitive.

  • Modify Paths

    Modify asset path attribute values.

  • Modify Point Instances

    Modifies point transforms and property values for individual point instances.

  • Motion Blur

    Adds time samples to allow motion blur when rendering.

  • Null

    This node does nothing. It can be useful to insert a Null into a network as a fixed point in the network that you can refer to by name in expressions/scripts.

  • Output

    Represents the output of a subnetwork. Allows you to design a node asset with multiple outputs.

  • Parent Constraint

    Makes a primitive appear to inherit the transform hierarchy of another prim somewhere else in the tree.

  • Points

    Creates or edits a Points shape primitive.

  • Points Constraint

    Position and Orient primitives using point positions from a geometry.

  • Primitive

    Bulk-creates one or more attributes of a certain type.

  • Prune

    Hides or deactivates primitives and point instances.

  • Python Script

    Lets you write Python code in the node to use the USD API to directly manipulate the stage.

  • RBD Destruction

    An example for a fracturing simulation in USD, also useful as a canned effect.

  • Reference

    References the contents of a external USD files and/or layers created by other LOP nodes into a branch of the existing scene graph tree. Can also remove or replace existing references.

  • Render Geometry Settings

    Applies renderer-specific geometry settings to geometry in the scene graph.

  • Render Product

    Creates or edits a UsdRenderProduct prim, which represents an output of a renderer (such as a rendered image file or other file-like artifact produced by a renderer), with attributes configuring how to generate the product.

  • Render Settings

    Creates or edits a UsdRenderSettings prim, which holds the general settings for rendering the scene.

  • Render Var

    Specifies a custom variable computed by the renderer and/or shaders, either a shader output or a light path expression (LPE).

  • Resample Transforms

    Generates interpolated transform time samples from existing time samples on USD prims.

  • Restructure Scene Graph

    This node has various operations for editing prim paths, variant sets, and composition arcs.

  • Retime Instances

    Offsets and/or scales the timing of animation on selected instances.

  • SOP Character Import

    Imports a character or animation from a SOP network into the USD scene graph.

  • SOP Create

    Lets you create geometry in a SOP subnetwork inside this node, so you can create geometry in-place in the LOP network instead of needing a separate SOP network.

  • SOP Crowd Import

    Imports a crowd from a SOP network into the USD scene graph.

  • SOP Import

    Imports geometry from a SOP network into the USD scene graph.

  • SOP Modify

    Converts USD geometry into SOP geometry, runs the SOP subnet inside this node on the geometry, and converts the changes back to USD overrides.

  • Scene Doctor

    Validates primitives on a USD stage.

  • Scene Import

    Imports models, materials, and lights from the Object level into the LOP network.

  • Scope

    Creates a scope primitive. Scope is the simplest form of grouping, and does not have a transform. Scopes can be useful for organizing the scene tree.

  • Set Extents

    Sets the bounding box metadata of selected primitives.

  • Set Variant

    Selects (switches to) one of the variants stored in a variant set on a primitive.

  • Simulation Proxy

    Generates low-poly collison geometry suitable for physical simulation and creates a proxy relationship to the original model.

  • Sphere

    Creates or edits a sphere shape primitive.

  • Split Point Instancers

    Splits a point instancer into two or more instances, which divide up the original instances.

  • Split Primitive

    Splits USD geometry prims into child primitives based on geometry subsets or primvar values.

  • Split Scene

    This node splits a scene graph into two disjoint sets of primitives.

  • Stage Manager

    Provides a convenient interface to reference in many files at once and place them in the scene graph tree.

  • Store Parameter Values

    Lets you store temporary (unsaved) data in the stage.

  • Sublayer

    Imports from USD files or other LOP node chains into as sublayers, or removes/replaces/reorders existing sublayers.

  • Subnet

    Encapsulates a LOP subnetwork, allowing you to organize and hide parts of the network.

  • Surface Constraint

    Constrain a prim to stick to a surface.

  • Switch

    Passes through one of several inputs, based on a parameter choice or expression.

  • TimeShift

    Outputs the stage as it is at a different point in the timeline.

  • Transform

    Edits the transforms of selected USD primitives.

  • Transform UV

    Moves, rotates, and scales texture coordinates on USD primitives.


  • USD Render ROP

  • Unassign Material

    Unbinds a material from one or more USD primitives.

  • Value Clip

  • Vary Material Assignment

    Assign different materials across a number of prims to create variation.

  • Volume

    References volume data on disk into a volume prim containing field prims.

  • Xform

    Creates or edits an Xform prim. Xform (and its sub-classes) represents a transform in the scene tree.