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See 
how to use TOP nodes for more information.
Task node (TOP) networks ¶
TOP networks contain task nodes that represent a series of tasks or work items to be performed. There are four main types of TOP node: processors that generate work items, schedulers that run the work item’s jobs, partitioners that join together incoming work items, and mappers that establish dependencies between otherwise unrelated work items.
With a TOP node network, you can create a scalable recipe for generating work items, running them locally or on a farm, establishing the network of dependencies between all the work items, and figuring out how to do it all as efficiently as possible. This recipe is called a PDG (Procedural Dependency Graph). For more information about TOPs and PDG, see Intro to TOPs.
Houdini creates a default task network (/topnet1) at /tasks, and a default scheduler (localscheduler) at /tasks/topnet1. Much like ROPs, you can create a standalone TOP network at any level of the scene. For example, you can create a TOP network in the /stage context to generate variations of LOP prims for a Solaris project.
The TOP level requires that you connect your nodes, all except for schedulers.
TOP flags ¶
For more information about how TOP nodes and their work items are visualized in the viewport, see PDG node network interface.
Icon |
Key |
Description |
|---|---|---|
|
Q or B |
Bypass disables the node, making it pass its channels through to the output unchanged. This is useful for testing and visualizing the effect the node is having in the viewport or on the output. When a node is bypassed, the flag on the left of the node is lit yellow. |
|
T |
Output sets this node’s output as the output of the TOP network. When the output flag is on, the flag on the right of the node is lit orange and an orange ring appears around the node. |
|
None |
Lock freezes the node’s work items so that they no longer update due to input or parameter changes. This prevents any changes to the work items.
When a node is locked, the flag second from the left on the node appears red and a snowflake-shaped badge appears next to the node. 
|
TOP badges ¶
Icon |
Meaning |
Description |
|---|---|---|
|
Node is dynamic |
When a TOP node is dynamic, a purple badge appears on the node. In TOPs, there are two types of nodes: static and dynamic. Static nodes can generate their work items without any inputs as they are not dependent on any upstream data. Dynamic nodes on the other hand require information from their inputs upstream to generate their work items. That is why dynamic nodes can only generate work items once they are cooking. To learn more about about static and dynamic TOP nodes and their significance in a TOP network, see Static vs. Dynamic. |
|
Node is locked |
This node’s work items are frozen or locked. See the Lock flag on the TOP node. |
|
Node is a locked HDA |
This node is a locked (synced) digital asset. |
Nodes ¶
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Creates and modifies array attributes on work items.
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Copies attributes from work items in one branch onto work items in another branch.
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Creates or sets an attribute on all incoming work items.
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Removes attributes from work items.
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Modifies dictionary attributes by adding key/value pairs, removing keys, or merging existing dictionaries
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Copies attributes and fields between work items, global attributes, and output files
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Create randomly-generated integer and float attributes on work items.
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Reduces array attribute values to a single value.
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Renames attributes on work items.
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Parses attribute values from a file into work items.
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Parses attribute values from a string, such as a file name.
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Starts a feedback loop. TOP nodes within the block execute serially, optionally looping for each incoming work item.
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Ends a feedback loop. TOP nodes within the block execute serially, optionally looping for each incoming work item.
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Copies data from a CSV file into work item attributes.
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Writes work item attributes to a CSV file.
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The PDG scheduler for Thinkbox’s Deadline software.
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Downloads the contents from one or more URLs into files.
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Edits the variables set in the environment work item command lines execute in.
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Issues warnings or errors when a condition is met.
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Encodes a sequence of still images as a video file.
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Extracts a sequence of still images from a video file.
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Compress files into an archive.
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Copies a file from one location to another, either at runtime or whenever the node generates.
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Decompresses archive files specified by incoming work items into individual files.
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Creates work items based on files that match a certain pattern.
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Creates a range of work items based on files that match a certain pattern.
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Deletes a file at a specified path.
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Renames or moves a file.
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Filters upstream work items by their attribute names or values
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Conditionally filters upstream work items.
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Filter upstream work items that fall within a specified frame or attribute range.
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Filters upstream work items by their state
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Generates work items with no attributes that run a command line.
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Loads points or primitives from a SOP or geometry file into work item attributes or a temporary file.
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Creates work items that cook a digital asset
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Schedules work items using HQueue.
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Starts a Houdini service block
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Provides easy access to ImageMagick functionality such as mass image convert, resize, and image mosaics.
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Controls the scheduling of in-process work items.
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Invokes a compiled block on input geometry
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Extracts data from JSON files and creates attributes
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Performs various operations that produce JSON output
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Utility TOP to Collect and Archive current HIP file dependencies
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Merges one or more text files into a single file.
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Labs Cut Geometry to Partitions
Cuts up incoming geometry
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Diffs a variety of geometry, text and image files.
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Extracts image metadata, such as the resolution, bit depth, color model, etc.
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Partition work items used for file caching
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Partitions and generates work items based on range and wedge values for file cache.
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Filters one or multiple work items by specific attribute values.
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Labs Generate from Imageplanes
Generates work items based on image planes found in an image
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Schedules work items on the local machine.
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Trains a neural network for regression.
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Starts a Maya service block
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Merge all upstream work items
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Creates work items based on matched nodes.
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Starts a Nuke service block
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Does nothing
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Notify an OP node that some TOP work has completed
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Provides easy access to the OpenImageIO’s command line tool, also known as oiiotool, to perform operations on images such as color space conversion, color mapping, resizing, text overlay, and box overlay.
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Subnet output
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Partitions work items based on their attributes
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Partitions source items spatially using the bounding items.
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Partitions work items into pairs, triples, etc
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Partitions work items using existing comparisons
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Partitions work items based on an expression
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Partitions work items based on their frame
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Partitions work items based on their index
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Partitions work items based on their feedback loop iteration.
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Partitions work items based on their node
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Partition work items based on range values
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Partitions work items spatially using axis-aligned bounding boxes.
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Execute Perforce commands through PDG
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Starts a Python service block
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Partitions work items using a Python script
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Generates work items using a Python script.
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A Python-based programmable Scheduler for PDG.
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Creates work items that run a Python script.
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Creates a Python virtual environment using TOPs
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Creates work items that cook an embedded Alembic ROP node
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Creates work items that cook an embedded Composite ROP node
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Creates work items that cook an embedded FBX ROP node
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Creates work items that cook a ROP node or network.
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Creates work items that cook an embedded Geometry ROP node
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Creates work items that cook an embedded Image ROP node
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Creates work items that cook an embedded Karma ROP node.
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Creates work items that cook an embedded Mantra ROP node
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Creates work items that cook an embedded OpenGL ROP node
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Creates work items that cook an embedded USD ROP node
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Extend the frame range of upstream work items and adds new work items as necessary
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Generates work items for the specified range.
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Connected to a remotely executing TOP graph and displays the nodes from that graph
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Creates work items that render an IFD file with Mantra
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Sends an email.
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Ends a service block.
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Sends code to a service block to execute.
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Creates a PDG service.
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Deletes a PDG service.
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Resets a PDG service.
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Starts a PDG service.
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Stops a PDG service.
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Creates ShotGrid entities
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Deletes entities from ShotGrid
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Downloads ShotGrid attachments
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Finds ShotGrid entities
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Starts a persistent ShotGrid command server
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Updates shotgun entities
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Uploads files to shotgun
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Sorts work items by a list of attributes
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Splits upstream items in two
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Splits upstream items into two using a fixed count
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Container for TOP nodes
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Switch which between network branches
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Cooks another TOP network.
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Input to a TOP fetch-ed network
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Writes text to a new file or appends to an existing file.
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Schedules work items using Pixar’s Tractor.
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Trains an OIDN model using preprocessed training and validation datasets.
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Creates work items that request data from a URL.
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Adds USD assets to the Asset Gallery.
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Fetches metadata, dependencies, and external references for a LOP Node or file.
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Creates work items from prims found in a USD stage.
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Creates work items from file references found in a USD stage.
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Modify asset path attribute values.
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Creates work items that render a USD file.
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Creates work items that render a USD file or LOP network
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Waits for all upstream work items to complete.
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Creates work items with varying attribute values.
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Expands file lists or partitions into multiple work items
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Import work items from a .json file or another TOP node.
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Extracts data from XML into Work Item attributes
