Houdini 18.5 Nodes LOP nodes

Switch

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

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Since 17.0

Overview

Sometimes you will use this node to interactively switch between several options, but more often you will use an expression to compute which input to pass through, based on some other input(s).

You can choose the input based on its position in the multi-input, or by name.

  • When Choose input is By index, you choose the input by its position (from left to right, starting at 0) in the connections to this node’s multi-input.

    • You can rearrange the inputs by clicking the Move up button next to an item in the list of inputs below the parameters.

    • Any expression you write in the Select input field should evaluate to a whole number.

  • When Choose input is By name, you choose the input by its name.

    • To rename an input, click in the "Input name" column on the input row in the list of inputs below the parameters, type the new name, and press Enter.

    • The Input name default parameter contains an expression to generate names for inputs that you haven’t named manually. The default (opinput(".", @input)) uses the name of the node connected to the input (this is the same name that is shown in "Input" column in the list of inputs below the parameters).

    • Any expression you write in the Select input field should evaluate to a string.

  • When Choose input is By pattern matching, you choose the input by assigning a pattern to each input, and comparing those patterns to the Select input value.

    • To set the pattern for each input, click in the "Match Pattern" column of the list of inputs below the parameters.

    • This style of input selection is useful when a context option or other expression needs to drive the input, but not according to a simple one to one relationship.

Tips

  • If the value in the Select input field does not correspond to an actual input, this node outputs an empty stage. This does not generate any warning or error.

  • Like the Null LOP, this node shares the same stage object between the input and output, so using it adds no real performance penalty unless the expression is slow to evaluate.

  • The Select input parameter is actually three different parameters, one for each possible value of the Choose input parameter. This is important if you're trying to script the parameters.

Parameters

Choose Input

Specifies how this node decides which input to pass through.

By Input Index

Choose the input by setting Select input to position of the connection in the multi-input (numbered from left to right, starting at 0).

By Input Name

Choose which input to pass through by setting Select input to its name.

By Pattern Matching

Choose which input to pass through by setting Select input to a value which is compared to the Match pattern of each input, starting with the input on the left and moving right. The first input with a pattern that matches the value is passed through.

Select Input (integer)

When Choose input is set to By index, the index of the input to pass through (the position of the connection in the node’s multi-input, from left to right starting at 0).

Select Input (string)

When Choose input is set to By name, the name of the input to pass through. The expression in the Input name default field computes a default name for each input (by default, the name of the node connected to the input), and you can rename inputs manually by clicking in the list of inputs below the parameters.

Select Input (string to pattern match)

When Choose input is set to By pattern matching, the value that is compared against each input’s pattern. You can set the pattern associated with each input by clicking in the Match pattern column of the list of inputs below the parameters.

Bad Input Response

Controls the behavior of this node if an invalid input is specified by the Select input parameter.

Output Empty Stage

An empty stage is output, ignoring all connected inputs.

Warn And Output Empty Stage

An empty stage is output, ignoring all connected inputs. In addition, a warning is added to this node.

Error

An error is added to this node, so nothing is output.

Clamp to Input Range

If the input is selected by integer index, and the value is less than zero, the first input is passed through. If the value is greater than the number of inputs, the last input is passed through. If the input is selected by name and the specified input name doesn’t exist, the first input is passed through.

Use Fallback Input

The Fallback input is used. If the Fallback input is also invalid, this will always generate an error, and nothing will be output from this node.

Fallback Input (integer)

When Choose input is By index and Bad input response is Use Fallback Input, the index of the input to pass through if Select input (integer) specifies an out of range input index.

Fallback Input (string)

When Choose input is By name or By pattern matching and Bad input response is Use Fallback Input, the name of the input to pass through if Select input (string) specifies an input name that doesn’t exist.

Input Name Default

Should contain an expression that computes a default name for inputs you haven’t explicitly given names. The expression can use the @input local variable ($IIDX is deprecated) to represent the index of the input for which to compute a name. The default (opinput(".", @input)) uses the name of the node connected to the input.

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.