Houdini 18.5 Nodes LOP nodes

Instancer

Instances or copies primitives onto points.

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Since 17.0

Overview

USD supports two types of instancing: instanceable primitives (where multiple copies of the same branch are aliases to shared storage) and point instancing (where USD stores points and prototypes to copy onto the points, but only draws the copies at render time). See USD instancing for more information.

This node can do both types of instancing: it can create a point instancer, or it can place instanceable prims based on the locations of points. (It can also reference in real separate copies instead of instanceable prims.)

The thing or things you want to create multiples of are called the prototypes. This node assumes the prototypes already exist, connected to the first or second input.

The points you want to instance/copy onto are called the targets. The targets can be points or prim positions in the input scene graph tree, or you can generate them in the SOP subnet inside this node, or in a SOP node elsewhere in the node hierarchy.

Example

  1. In the network editor, use the ⇥ Tab menu to create a Torus.

    The "Torus" tool actually creates a SOP Create node that imports the result of a Torus SOP into USD.

    On the SOP Create node, set the Import path prefix to /Geometry/torus.

  2. Add a Sphere LOP. Set the Primitive path to /Geometry/ball and the Uniform scale to 0.05.

  3. Add a Cone LOP. Set the Primitive path to /Geometry/cone and the Uniform scale to 0.05.

  4. Add a Cylinder LOP. Set the Primitive path to /Geometry/tube and the Uniform scale to 0.05.

  5. Add an Instancer LOP.

    • Set the Primitive path to /Geometry/shapes.

    • Set the Method to "Point instancer".

    • Set the Location source to "First input’s points".

    • Set the Location primitives to /Geometry/torus/mesh_0.

    • Set the Prototype source to "First input".

    • Set the Prototype primitives to /Geometry/ball /Geometry/cone /Geometry/tube.

    • Set the Prototype index to "Random"

    The node randomly instances a ball, cone, or tube at each point of the torus.

Parameters

General

Primitive Path

The scene graph path at which to create the point instancer prim (when Method is "Point instancer"), or the parent of all created prims (when Method is anything other than "Point Instancer").

Primitive Kind

If the prim at Primitive path doesn’t exist, this node creates it. If it creates the prim, it sets this as the prim’s kind.

Method

See Instancing in USD for more information.

Point Instancer

Create a point instancer. This is a single prim (with the prototypes as children) that draws the instanced geometry on-demand in the viewer or renderer.

Instanceable Reference

Creates an instanceable prim at each point. These are separate prims in the scene graph tree, and can individual overrides on each top-level prim, but they share a "shadow" copy of their descendant prims, so their descendants are not editable or individually override-able.

Reference

Creates a separate prim at each point that references in the "prototype" prim(s). These references take up more storage space than instanceable prims, but you can edit/override the descendant prims.

Instanceable Inherit

Just like "Instanceable Reference" except the instance primitives inherit from the source primitive rather than reference it.

Inherit

Just like "Reference" except the instance primitives inherit from the source primitive rather than reference it.

Instanceable Specialize

Just like "Instanceable Reference" except the instance primitives specialize from the source primitive rather than reference it.

Specialize

Just like "Reference" except the instance primitives specialize from the source primitive rather than reference it.

Target Points

Location Source

Where to get the points to copy onto.

Internal SOP

Build a SOP network in the subnet inside this node to generate the points.

External SOP

Get the points from the output of a SOP elsewhere in the Houdini node hierarchy.

First input’s primitives

Use the positions of primitives in the first input as the target points.

First input’s points

Get the points from a geometry prim, or the positions from another point instancer in the first input.

SOP Path

When Location source is "External SOP", the node path of the SOP node that generates the target points.

Point Group

When Location source is "Internal SOP" or "External SOP", get the points from this named group in the SOP geometry.

Location Primitives

When Location source is "First input’s primitives", this is the scene graph paths of the primitives whose positions you want to use as target points. When Location source is "First input’s points", this is a the scene graph path(s) of one or more geometry prims containing target points (such as a polygonal mesh). In either case you can use pattern syntax to select multiple primitives.

Prune Mode

You can delete or hide a certain percentage of the target points. This may be useful if the target points come from an overly dense point cloud, or to speed up display when you're first setting up the instancer. The default is "None" to not delete or hide any points.

Prune Amount

When Prune mode is "Delete" or "Set visibility", the percentage of points to delete or hide. This can be used to improve performance while setting up the operator.

Set Orientation

Rotate the instanced primitives based on standard instancing SOP attributes on the points. These SOP attributes include N, up , and orient.

Set Scale

Scale the instanced primitives based on standard instancing SOP attributes on the points. These SOP attributes include scale and pscale.

Make Transform Source Primitives Invisible

Set the visibility of the Location primitives to "hidden" in the output. The default is on.

Point Attributes to Copy

A list of attributes on the template points to copy to instances. When creating a Point Instancer, an array primvar will be created for each listed attribute, with an entry for each point’s value. When creating reference primitives, an attribute of the same name and type will be created on each primitive.

Primitive Naming

These parameters are visible when Method is "References" or "Instanceable references".

Instance Base Name

A prefix string for the names of prims created by this node. The node appends the point index to this string to create each name. This name is then appended to the Primitive path value to create the reference prim path. This is ignored if Use path attribute is on (below) and the path attribute exists.

Use Path Attribute

Use a string attribute on the target points to create the reference prim path.

Path Attribute

When Use path attribute is on, the name of a string attribute on each point containing the path to use for the prim created at that point. The path in this attribute is appended to the Primitive path value. If this attribute doesn’t exist, the node falls back to using Instance base name.

If the paths in the attribute aren’t unique, the node will only create one reference per path. In this case the node will show a warning.

Prototypes

Prototype Source

Whether the prim(s) you want to reference/instance onto the points is/are in the first input or the second input.

Prototype Reference Type

If Prototype source is "First input", this parameter controls the composition type to use when creating references to the source primitives from within the "Prototypes" folder in the scene graph. This parameter can be "Reference", "Inherit", or "Specialize". See inherits and specializes for more information about how these choices differ from a simple reference.

Make Prototype Source Primitives Invisible

If Prototype source is "First input" and this is on, the node sets the visibility of the prims used as primitives to "hidden" in the output. The default is on.

Use Entire Stage as Prototype

If Prototype source is "Second input" and this is on, the node copies everything from the second input’s scene graph tree under a new prim and uses that as the prototype. This lets you build a node chain that builds the prototype and connect it to the second input, and not have to specify which prim in the second input to use.

Prototype Parent Kind

When Use entire stage is on, this sets the kind of the prim the node creates as a parent for root prims from the second input. The default is None.

Prototype Primitives

The scene graph path(s) of the primitive(s) you want to use as prototype(s). You can use pattern syntax to select multiple primitives.

Prototype Index

Random

Choose the prototype at each point randomly.

Index

Specify a single prototype to use at each point in a parameter. This lets you drive the parameter using an expression (for example, based on a context option).

Index Attribute

Use the value of an integer attribute on the target point as an index into the list of prototypes.

Name Attribute

Use the value of a string attribute to select the prototype by name. (The name of each prototype is copied from the original prim used to create the prototype. The node may add numbers to the prototype names to make them unique.)

Seed

When Prototype index is "Random", the seed for the random number generator.

Index

When Prototype index is "Index", the index of the prototype to use, from the list of primitives in Prototype primitives. You can use an expression to choose the index based on some other factor.

Index Attribute

An integer attribute on the target points that specifies the prototype to use.

Name Attribute

A string attribute on the template points that specifies the name of the prototype to use.

Note

USD Point Instancer primitives don’t inherently have the ability to address prototypes by name. This node finds the prototype by name, then sets the corresponding index in the protoIndices array attribute on the point instancer prim.

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.

  • 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.

  • 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.

  • 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 a collection using selected prims.

  • Collection

    Creates/edits collections using primitive patterns.

  • 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.

  • 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 Properties

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

  • Edit Prototype

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

  • 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.

  • Follow Path Constraint

    Constrains a prim to follow a path curve.

  • For Each

    The end node of a For-Each loop block.

  • 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.

  • 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.

  • Karma Procedural

    Sets up render-time instantiation for Karma.

  • Karma Render Properties

    Configure Render Properties for Karma (Beta).

  • Karma Standard Render Vars

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

  • LOP nodes

    LOP nodes generate USD describing characters, props, lighting, and rendering.

  • 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.

  • Light

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

  • 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.

  • 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.

  • Mesh

    Creates or edits a mesh shape primitive.

  • Modify Point Instances

    Modifies point transforms and property values for individual point instances.

  • 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 of how to a fracturing simulation in USD, also useful as a canned effect.

  • Reference

    References the contents of an external USD file into a branch of the existing scene graph tree, or removes/replaces 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).

  • Retime Instances

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

  • 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 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 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 Primitive

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

  • 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

  • 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.