Houdini 18.0 Nodes LOP nodes

Configure Stage

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

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Overview

This node authors metadata which affects which layers and which parts of the stage are composed. This is useful to reduce processing times when working interactively. You can use it to limit the scope of operation of following LOP nodes.

The stage population mask and layer muting features let you limit what is loaded and composed into the scene graph tree.

(Similarly, viewer load masks can control what is shown in the viewer, but the full USD is still loaded and processed, while this node can limit what is loaded and processed in the first place.)

If you are using an asset resolver, this node also provides a way to specify a configuration file for the resolver.

Tips

  • Because LOP nodes in a chain share a USD stage, changes you make here affect all following nodes in the chain (through first inputs to outputs).

  • For subsequent Merge nodes, the list of muted layers is the union of the muted layers set on all inputs, and the output stage population mask is the union of the stage population masks on all inputs.

  • If a Viewport Load Mask is set on a stage that has been configured with a stage population mask or layer muting by this node, the data to appear in the viewport will be restricted by both sets of layer muting and stage population masks. This means the union of all muted layers and the intersection of the two population masks. Note the difference compared to the Merge node, which takes the union of all stage population masks.

Parameters

Populate Primitives

How/whether to edit the stage population mask.

Don’t Change

Does not change the current stage population mask.

Add and Remove Primitives to Populate

Use the parameters below to add or remove primitive paths to/from the population mask.

Set Primitives to Populate

Discard the current stage population mask and replace it with the paths in the parameters below.

Populate All Primitives

Discard the current stage population mask and replace it with a mask that populates all primitives.

Populate Paths from Input

When Populate primitives is "Add and Remove" or "Set Primitives", this is a list of primitive path patterns matching prims to include. The difference between this and Populate paths is that this parameter selects from prims that exist in the input.

Remove Populate Paths from Input

When Populate primitives is "Add and Remove", this is a list of primitive path patterns matching prims to remove. Removing a primitive from the stage population mask means the resulting primitives will no longer exist in the output stage. The difference between this and Depopulate paths is that this parameter selects from prims that exist in the input.

Populate Paths

When Populate primitives is "Add and Remove" or "Set Primitives", this is a list of explicit paths (no patterns allowed) of prims to include. The difference between this and Populate input paths is that this parameter can add paths to the mask even if this node has no input, and even if the prims don’t exist at the paths yet, but might be created by subsequent nodes.

Remove Populate Paths

When Populate primitives is "Add and Remove", this is a list of explicit paths (no patterns allowed) of prims to remove. Removing a primitive from the stage population mask means the resulting primitives will no longer exist in the output stage. The difference between this and Depopulate input paths is that this parameter can remove paths from the mask even if this node has no input, and even if the prims don’t exist at the paths yet, but might be created by subsequent nodes.

Load Primitives

How/whether to edit the set of primitives which should load their payloads.

Don’t Change

Does not change the current set of payloads to load.

Add and Remove Primitives to Load

Use the parameters below to add or remove primitive paths to/from the set of payloads to load.

Set Primitives to Load

Discard the current set of payloads to load and replace it with the paths in the parameters below.

Load All Primitives

Discard the current set of payloads to load and replace it with a flag that causes the payloads on all primitives to load.

Load Paths from Input

When Load primitives is "Add and Remove" or "Set Primitives", this is a list of primitive path patterns matching prims to load. The difference between this and Load paths is that this parameter selects from prims that exist in the input.

Remove Load Paths from Input

When Load primitives is "Add and Remove", this is a list of primitive path patterns matching prims to remove. Removing a primitive from the set of payloads to load means the resulting primitives will no longer compose their payload arcs on the output stage. The difference between this and Unload paths is that this parameter selects from prims that exist in the input.

Load Paths

When Load primitives is "Add and Remove" or "Set Primitives", this is a list of explicit paths (no patterns allowed) of prims to include. The difference between this and Load input paths is that this parameter can add paths to the set even if this node has no input, and even if the prims don’t exist at the paths yet, but might be created by subsequent nodes.

Remove Load Paths

When Load primitives is "Add and Remove", this is a list of explicit paths (no patterns allowed) of prims to remove. Removing a primitive from the set of payloads to load means the resulting primitives will no longer compose their payload arcs on the output stage. The difference between this and Unload input paths is that this parameter can remove paths from the set even if this node has no input, and even if the prims don’t exist at the paths yet, but might be created by subsequent nodes.

Mute Layers

How/whether to edit the set of muted layers.

Don’t Change

Doesn’t change the current set of muted layers.

Add and Remove Layers to Mute

Use the Mute paths and Unmute paths to add/remove layers to/from the set of muted layers.

Set Layers to Mute

Replace the current set of muted layers with the paths in Mute paths.

Unmute All Layers

Discard the current set of muted layers, no layers are muted in the output.

Mute Paths

When Mute layers is "Add and Remove" or "Set Layers", this is a list of paths to layers to mute. Even if the layers listed here do not exist on the inputs stage (if any), this set of paths will be remembered by the stage, and loading of the named layers will be prevented in subsequent nodes.

Unmute Paths

When Mute layers is "Add and Remove", this is a list of paths to layers to unmute (if they are currently muted).

Resolver Context Asset Path

A path to a file containing configuration information for the asset resolver. The standard USD asset resolver and Houdini’s built-in asset resolver do not use this, but if you use a custom asset resolver, it may read this file to change its settings when loading layers for this stage.

The contents of this file, whether it is used at all, and if it’s used, how it affects the behavior of the asset resolver, is completely up to asset resolver implementation.

For example, the configuration file might specify a version number, telling the resolver to prefer assets of that version when loading resources.

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.

  • 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 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • Extract Instances

    Converts 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 Subset VOP

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

  • Graft

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

  • Inline USD

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

  • 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.

  • 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

  • Look At Constraint

    Constrains a prim to always point toward a target.

  • Material Library

    Imports Material VOP nodes as USD material prims.

  • 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.

  • Modify Point Instances

    Modify 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 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.

  • 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.

  • 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.

  • attribvop