Houdini 20.5 Nodes LOP nodes

Duplicate

Creates copies of a prim (and its descendants).

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Since 18.0

Overview

There are many ways to make “copies” in USD, and how to integrate the copies into the scene graph tree. This node can perform many of them.

Tips

  • You can specify more than one source prim. In that case the node will duplicate each source prim (and its descendants) in turn.

  • You can apply a transform to each copy. For example, for prims holding geometry, you can add a translation to move the geometry copies apart from each other.

  • If this node generates duplicate paths where intermediate prims don’t exist, it will automatically create them. Use the Parent primitive type to set the type of the created intermediate prims.

  • You can create a USD collection of the duplicates using the Collection primitive and Collection name parameters.

  • You can promote collections inside the copied prim onto another prim.

Parameters

Source Primitives

The primitive(s) the node should operate on. You can drag primitives from the scene graph tree pane into this textbox to add their paths, or click the Reselect button beside the text box to select the primitives in the viewer, or ⌃ Ctrl-click the Reselect button to choose prims from a pop-up tree window. You can also use primitive patterns for advanced matching, including matching all prims in a collection (using /path/to/prim.collection:‹name›).

Note

This parameter needs to be exposed in order for the transform handles to be context-aware. Without it, the handles may not be positioned properly.

Modify Source Primitive

What to do with the original source prim.

Deactivate Source Primitives

Do not include the source primitive in the duplicates, and set the source prim to “inactive”.

This is the default, and allows each duplicate of the source to be treated separately. Overrides of attributes on any individual duplicate prim will not affect any of the other duplicates. It also prevents changes from being made to the source primitives (which would affect all of the duplicates).

Hide Source Primitives

Do not include the source primitive in the duplicates, and set the visibility of the source prim to “invisible”.

The source prim (and its descendants) will not appear in the view, but you can still edit it and those changes will affect the duplicates.

Source Primitives Are First Duplicates

Treat the source primitive as one of the duplicates, so the number of duplicates created is actually the specified total number minus one.

Changes to this “first duplicate” will affect all the other duplicates. But changes to the other duplicates will not affect each other.

Source Primitives Are Classes

Assume that the source primitive is a class primitive (see USD documentation for more information about the class specifier). This means the source primitive is not included in the duplicates, and the node doesn’t set the visibility or activation values of the duplicates.

Source Primitives Are Deactivated

Assume the source primitive is currently deactivated. This means the source primitive is included in the duplicates, and the node sets the activation of the duplicates to true.

Source Primitives Are Hidden

Assume the source primitive is currently hidden. This means the source primitive is not included in the duplicates, and the node sets the visibility of the duplicate primitives to “inherits”.

Total Number

The total number of copies of the source object that should exist (and be active) after the duplicate operation. The Modify source primitive setting affects whether this includes the original or not.

Separate Source and Destination Paths

By default, the copies are children of the same parent as the original. Turn this option on if you want to put the copies under a different parent prim.

Destination Primitives

When Separate Source and Destination Paths is on, this is the path to the parent prim for the duplicates.

Duplicate Name

Enter a string expression (remember to enclose the expression code in backticks) to compute the name for each duplicate prim. Each name must be unique among its siblings. The default expression adds an underscore and a number (starting at zero) to the name of the original. You can use the following local variables:

@copy ($CY is deprecated)

Which copy number is being created.

@numcopy ($NCY is deprecated)

Total number of copies that will be created.

@src ($SRC is deprecated)

Which source primitive index is being copied.

@numsrc ($NSRC is deprecated)

The number of source primitives that are being duplicated.

@srcname ($SRCNAME is deprecated)

The name of the source primitive being duplicated.

@srcpath ($SRCPATH is deprecated)

The path of the source primitive being duplicated.

Primitive definition

Reference Type

The type of composition arc used to connect the duplicates to the original. Use the default (“Reference”) unless you have a specific reason to choose Inherits or Specializes.

Note that there is also a “Copy” option. This is not a USD composition arc but, rather, is a mode that explicitly copies (reauthors) the source prim(s) data into the duplicate location(s).

Make Instances

When this is on, each of the duplicates is marked as an instanceable prim. This means they will be “aliases” to an implicit shared “master” prim. The advantage is that instances take a very small amount of constant space. The disadvantage is that while you can edit attributes on each instanced prim (for example, give each instance its own transform), you can’t edit any of its descendants.

Parent Primitive Kind

The Kind to set on the parent prim.

None

Set the prim to have no kind.

Automatic

Automatically choose a kind based on the parent and child kinds.

Assembly

Mark this prim as an “important” group of models (for example, if a prop is made up of smaller moving parts, the top level of the prop would be an Assembly, and the sub-parts would be Groups and/or Components).

Group

Mark this prim as a group of models.

Component

Mark this prim as a “leaf” model.

Sub-component

Mark this prim as a subordinate part under a Component model.

Parent Primitive Type

If this node generates duplicate paths where intermediate prims don’t exist, the node will automatically create them. This sets the type of the created intermediate prims.

Collections

Collection Primitive

If you want to create a collection of the duplicates, set the path to a prim to attach the collection to, and set Collection name.

Collection Name

If you want to create a collection of the duplicates, set Collection primitive, and set this to the name of the collection.

Promote Collections

If the source prim or any of its descendants have a collection that match this pattern (or space-separated list of patterns), the node authors a copy of the collection on the Collection primitive. If the source(s) have multiple collections with the same name, the contents of the new authored collection contains the union of their contents.

For example, when this is on, if you duplicate /Geometry/orig to /Geometry/dupe1 and /Geometry/dupe2, if orig had a collection named lights containing /Geometry/orig/lamp, the collection will be “promoted” onto the common parent (/Geometry) and the contents will be rewritten to be relative to the duplicates. So /Geometry would have a collection lights containing /Geometry/dupe1/lamp and /Geometry/dupe2/lamp.

Promote Source Collections

See the help for Promote collections. If promote collections is on and this is on, the original contents of the collection that gets promoted is included in the promoted collection, along with the paths that were rewritten to be relative to the duplicate prims.

Continuing the example from the Promote collections help, if this is on, the “promoted” collection on /Geometry would not only contain /Geometry/dupe1/lamp and /Geometry/dupe2/lamp, but also the original contents of the pre-promoted collection, /Geometry/orig/lamp.

Transform Cumulative

The transform below is applied cumulatively to each copy. For example, when this is on, and Rotate X is 5, the X rotation of the first copy is 5, the second copy is 10, the third copy is 15, and so on.

Transform order

The order in which Houdini applies translates, rotates, and scales, and the order in which it applies rotation.

Translate

Movement amount along XYZ axes.

Rotate

Degrees rotation around XYZ axes.

Scale

Non-uniform scaling along XYZ axes.

Uniform scale

Scales the object uniformly along all three axes.

Pivot Transform

Pivot translate

Moves the local origin of the object.

Pivot rotate

Rotates the local origin of the object after translation.

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.

  • Draw Mode

    Sets draw mode properties on USD model assets.

  • 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 From Node

    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 Color

    Adds display color and display opacity primvars to geometry.

  • 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: Crowd

    Houdini Crowd Procedural for Solaris.

  • Houdini Procedural: Hair

    Houdini Hair Procedural for Solaris.

  • Houdini Procedural: Ocean

    Houdini Ocean Procedural for Solaris.

  • Houdini Procedural: RBD

    Houdini RBD 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.

  • 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 Products

    Create multiple render products sharing common settings.

  • Karma Render Properties

    Configure Render Properties for Karma.

  • Karma Sky Atmosphere

    Creates or edits a Karma Sky Atmosphere.

  • 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 Karma AOVs for RenderMan Denoiser

    Generates AOVs for the Pixar RenderMan denoiser.

  • 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 ROP

  • 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.