Houdini 19.0 Nodes LOP nodes

Retime Instances

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

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Since 18.0

Overview

This node offsets and/or scales the timing of animation on certain instances. Since USD doesn’t allow destructive editing, it does this by creating new versions of the instances' prototypes, and overriding the instances to refer to the new prototypes.

This node has two ways of specifying per-instance offsets and scales:

  • You can get per-instance offsets and/or scales from primvars.

  • You can create a SOP network inside this node (or elsewhere in the Houdini node hierarchy) that generates a point cloud where each point corresponds to an instance and SOP attributes on the points specify offsets and scales. See point cloud editing below.

Tip

You can offset/scale the animation on regular prims with the Time Shift LOP. If you use Time Shift on an instancer, it will affect all instances equally, whereas this node lets you retime instances individually.

Point cloud editing

This node lets you build a SOP network to specify offsets and scales by processing points geometry that represents the instances.

  • If you choose “Internal SOP”, the node uses the nodes you build in the SOP subnet inside this node.

    • In this mode, the points are created for you and fed through the network (connect the output of Sub-Network Input #1 to the first node in your processing network).

  • If you choose “External SOP”, you can specify a SOP network anywhere in the Houdini node hierarchy. However, the network must generate the points with the proper attributes somehow.

    • The points must have a path SOP attribute set to the scene graph path of the instancer.

    • By default, the node will try to match points up with instances by matching point numbers to instance indices. This will probably only work you are processing every instance in a single instancer. Otherwise, you should turn on Match by ID and set the id SOP attribute on each point to the index of the corresponding instance.

  • The points should have frameoffset and/or timescale SOP attributes on the points to specify the offset and scale to apply to the corresponding instance.

Tips and notes

  • This node works best for offsetting/scaling the animation on large groups of instances, or all instances that share a certain prototype. Since each separate timing requires a separate prototype, if you try to give each instance a different offset/scale, you will essentially “de-instance” the point instances (by having the same number of instances and prototypes).

  • If you are retiming prototypes created dynamically on an in-memory layer, you need to have a Cache LOP upstream from this node, so all frames are cooked and available.

    If the instances come from an external USD file, you don’t need a Cache, since the file should contain all the needed time samples.

  • By default, retiming prototypes will not affect the instance transforms or primvars (unless they are defined on the prototype prims themselves).

    You can choose to retime transforms and primvars defined at the instance level with the Retime transforms and Retime primvars parameters.

  • This node is optimized to only create new retimed prototypes for each unique combination of frame offset and time scale. However, this node still usually has to do a lot of work, and can be slow.

Parameters

Type

Whether you want to retime point instances, or instanceable primitives.

Instances

A space-separated list of instances, using /path[instance_index] syntax (for example, /geometry/instancer[0] /geometry/instancer[1]). To select all instances in an instancer, use /path[*]. To select a range, use /geometry/instancer[4-7] (the range is inclusive). To select instances inside nested instancers, use multiple indexes, for example /geometry/instancer[2][7].

Instances

When Type is “Native Instances”, a list of paths to instanceable prims.

Retime Using

How to compute the transform for each selected instance.

Internal SOP

Uses the SOP subnet inside this node to process points representing the instances.

External SOP

Uses an external SOP network that must generate points representing the instances from scratch. (See point cloud editing above.)

Primitive Properties

Gets the offset/scale primvars on the instancer/instance primitives themselves.

Random Values

Creates a set number of random offsets and scales distributed across instances.

Match By ID

When Modify Using is “External SOP” and this is on, the node looks for id SOP attributes on the generated points. The id should be the index of the corresponding instance. (When this is off, the node matches point numbers to instance indices, which only works if you process every instance in a single instancer.)

SOP Path

When Modify Using is “External SOP”, the node path to the geometry node to cook to get the generated points. Each point in the output should correspond to one of the selected instances.

Group

When Modify Using is “External SOP”, if this is not blank, only consider points in this point group.

Retime Prototypes

Create retimed prototypes for the specified instances. When instance animation is driven by instance-level transforms, turning this off will greatly improve performance.

Retime Transforms

Even if instance transforms are animated, by default this node does not affect them. Turn this on to re-time transform animation as well.

Retime Primvars

Even if instance-level primvars are animated, by default this node does not affect them. Turn this on to re-time primvar animation as well.

Use Frame Offset

Enable frame offsets to drive the instance retiming. This timeshifts the instance animation.

Use Time Scale

Enable time scales to drive the instance retiming. This slows down or speeds up the instance animation.

Attribute

When Retime Using is “Internal SOP” or “External SOP”, the name of the SOP point attribute that should specify the frame offset or time scale for each instance.

Primvar

When Retime Using is “Primitive properties”, the name of a primvar on the instancer that should specify the frame offset or time scale for each instance.

Variations

When Retime Using is “Random Values”, specify the total number of unique frame offset or time scale values.

Min/Max

When Retime Using is “Random Values”, specify the minimum and maximum values for the frame offset or time scales.

Seed

When Retime Using is “Random Values”, specify the seed to use when generating a random number for each instance.

Distribution

When Retime Using is “Random Values”, allows the user to control the distribution of the random values between the specified Min/Max.

Global Frame Offset

Apply this offset to all instances equally, in addition to any per-instance offsets.

Global Time Scale

Apply this time scaling factor to all instances equally, on top of any per-instance scales.

See also

LOP nodes

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    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

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  • Attribute VOP

    Create/edit USD attribute values using a VOP network.

  • Attribute Wrangle

    Create/edit USD primitive attributes using a VEX snippet.

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  • Background Plate

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  • 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.

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    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.

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    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

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  • Configure Primitives

    Edits various metadata on one or more primitives.

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    Creates or edits a cube shape primitive.

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

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

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    Runs a simulation to drop primitives under gravity.

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    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

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  • 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 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.

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    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.

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    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.

  • Instancer

    Creates a constant volume within a box.

  • Instancer

    Create multiple render products sharing common settings.

  • Karma

    Renders the USD scene using Houdini’s Karma renderer.

  • Karma Procedural

    Sets up render-time instantiation for Karma.

  • Karma Render Properties

    Configure Render Properties for Karma.

  • Karma Standard Render Vars

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

  • LOP nodes

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

  • LPE Tag

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  • Labs RizomUV Optimize

  • Labs RizomUV Rectangularize

  • Labs RizomUV Unwrap

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  • Layer Replace

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    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

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

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    Constrains a prim to always point toward a target.

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    Authors USD material primitives from shader VOP nodes.

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    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 Paths

    Modify asset path attribute values.

  • Modify Point Instances

    Modifies point transforms and property values for individual point instances.

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    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.

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    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.

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  • 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.

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    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.

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  • SOP Import

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

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

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

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

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

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

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

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    Constrain a prim to stick to a surface.

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    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

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    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.

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    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.