Houdini 18.5 Nodes TOP nodes

TOP Fetch TOP node

Cooks another TOP network

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Since 17.5

This node can be used to cook a different TOP network. The other network can exist in the same .hip file or an external file, and will be cooked via the active scheduler. The other TOP network is evaluated in a separate process from the current one.

This node works in two steps. First work items are generated to cook the external TOP network referred to by the TOP Path parameter. The attributes and input files associated with each work in this node are made accessible to the fetched network using the standard work item JSON format. The path to the JSON file is exported as $PDG_FETCH_JSON_FILE in the environment used to cook the fetched network. The fetched network can use a TOP Fetch Input node to load that work item into its own network.

When the remote TOP network is cooked, the work items on the output node of that network are saved to disk and reported back to PDG. Then these items are re-created in the topfetch node. The items visible on the topfetch node are those re-created items.


The $HH/help/files/pdg_examples/top_topfetch example shows how you can use this node to fetch a TOP network.


TOP Fetch

Generate When

Determines when this node will generate work items. You should generally leave this set to "Automatic" unless you know the node requires a specific generation mode, or that the work items need to be generated dynamically.

All Upstream Items are Generated

This node will generate work items once all of the input nodes have generated their work items.

All Upstream Items are Cooked

This node will generate work items once all of the input nodes have cooked their work items.

Each Upstream Item is Cooked

This node will generate work items each time a work item in an input node is cooked.


The generation mode is selected based on the generation mode of the input nodes. If any of the input nodes are generating work items when their inputs cook, this node will be set to Each Upstream Item is Cooked. Otherwise, it will be set to All Upstream Items are Generated.

TOP Path

The path to the TOP network within the .hip file specified in the Hip File Path parameter.

Hip File Path

The path to the .hip file that contains the TOP network to fetch.


TOP Scheduler Override

This parameter overrides the TOP scheduler for this node.

Work Item Priority

This parameter determines how the current scheduler prioritizes the work items in this node.

Inherit From Upstream Item

The work items inherit their priority from their parent items. If a work item has no parent, its priority is set to 0.

Custom Expression

The work item priority is set to the value of Priority Expression.

Node Defines Priority

The work item priority is set based on the node’s own internal priority calculations.

This option is only available on the Python Processor TOP, ROP Fetch TOP, and ROP Output TOP nodes. These nodes define their own prioritization schemes that are implemented in their node logic.

Priority Expression

This parameter specifies an expression for work item priority. The expression is evaluated for each work item in the node.

This parameter is only available when Work Item Priority is set to Custom Expression.


FetchingATopNetwork Example for TOP Fetch TOP node

This example demonstrates how to use Top Fetch node to execute a TOP network out of process and return the results.

See also

TOP nodes