Houdini 20.0 Nodes

TOP nodes

TOP nodes define a workflow where data is fed into the network, turned into “work items” and manipulated by different nodes. Many nodes represent external processes that can be run on the local machine or a server farm.

On this page

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.




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.


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.


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.

  • Work items on a locked node cannot have dependencies on work items outside their node, but they can still be used as inputs for other nodes.

  • Unlocking the node discards all its 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




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.