Houdini 20.0 Unreal

Houdini Engine Plugin Settings

A quick reference for console commands in Houdini Engine.

On this page

The plugin settings allows you to change the behavior and values of multiple options for Houdini Engine for Unreal.

To access these settings: In the Unreal Engine main menu, select Houdini Engine then PluginSettings. A new window pops up with the plugin settings.

Session

See Start a Session for more information.

Note

You must restart Unreal Engine when you change the sesssion type or its configurations.

Setting

Description

Session Type

Selects the session type from the options the following options:

  • TCP Sockets

  • Named pipe or domain socket

  • None - Select this option to create a Houdini Engine sessions without a license

Server Host

For TCP Sockets session types. Enter the IP address or host name

Server Port

For TCP Sockets session types. Enter the server port

Server Pipe Name

For Named pipe or domain socket session types. Enter the server pipe name

Start Automatic Server

When on, the server automatically starts Houdini Engine when you open a session

Automatic Server Timeout

Enter the value in milliseconds before the server connection times out

Advanced (Session)

The session’s advanced tab gives you additional settings for Session Sync.

Setting

Description

Sync With Houdini Cook

When on, changes made in Houdini automatically updates to Unreal

Cook Using Houdini Time

When on, uses the Houdini timeline to cook assets

Sync Viewport

When on, syncs the Unreal and Houdini viewport

Sync the Houdini Viewport To Unreal’s viewport

When on, syncs Houdini’s viewport to Unreal’s viewport

Sync the Unreal Viewport To Houdini’s viewport

When on, syncs Unreal’s viewport to Houdini’s viewport

Instantiating

Setting

Description

Show Multi Asset Dialog

When on, a dialog appears to select an asset when instantiating an HDA with multiple assets

When off, the first asset is instantiated

Prefer HDA Memory Copy Over HDA Source File

When on, the memory copy of an HDA is instantiated over the latest version of the .HDA file. You need to reimport the HDA .UAsset to get the latest changes from the source .HDA

When off, the source .HDA file is instantiated when available. This fallbacks to the memory copy if the source file cannot be found

Cooking

These settings change the default values when you instantiate new assets. You can also override these values per asset in the Houdini Asset options.

Setting

Description

Pause Cooking on Start

When on, cooking Houdini assets is paused when starting Unreal

Display Slate Cooking Notifications

When on, disables the cooking and instantiating notifications

Default Temporary Cook Folder

Set the default path for the temporary folder when cooking assets

Default Bake Folder

Set the default path for the temporary folder when baking assets

Geometry Marshalling

This section lists properties when you transfer data between Houdini Engine and Unreal.

Setting

Description

Landscape - Use default Unreal scaling

When on, landscapes use the default Unreal scaling

This causes loss in some precision on the Z-axis but uses the same transforms as Unreal’s landscapes

Landscape - Use full resolution for data conversion

When on, landscapes uses the full range of values available when you convert heightfield data to landscapes

This results in greater precision but prevents landscapes being sculpted higher or lower than the min/max value

Landscape - Force Min/Max values for data conversion

When on, forces the min/max values when you convert the heightfield to landscape. You set the the min and max values in the next settings

This can be useful if you use multiple HDAs that generates landscapes and want similar values

Landscape - Forced min Value

Sets the minimum value for landscape conversion. Force Min/Max values for data conversion must be on

Landscape - Forced max Value

Sets the maximum value for landscape conversion. Force Min/Max values for data conversion must be on

Curves - Add rot & scale attributes on curve inputs

When on, your HDA’s input have additional rot and scale attributes set per curve point

Curves - Use Legacy Input Curve

When on, creates curve 1.0 nodes for its inputs instead of manually creaing the curve geometry using HAPI

Curves - Default Spline Resolution (cm)

Set the spline sample length in cenntimeters when converting Unreal Spline Components to Houdini Curves. Set to 0 to only send the control points

Static Mesh

This section lists settings when you create static meshes.

Setting

Description

Enable Proxy Static Mesh

When on, creates a Houdini proxy mesh before a static mesh

Proxy meshes generates faster than static meshes and allows for faster iterations

Show Default Mesh

When on, a default mesh is spawned when an instancer or mesh socket fails to find its assigned mesh

Prefer Nanite Fallback Mesh

When on, selects the Nanite fallback mesh when a Nanite asset is used in the Houdinin input

Advanced (Static Mesh)

Setting

Description

Refine Proxy Mesh After a Timeout

When on, the proxy mesh is refined to a static mesh after an of timeout

Proxy Mesh Auto Refine Timeout (seconds)

For Refine Proxy Mesh After a Timeout setting. Set the timeout value in seconds to trigger auto-refinement

Refine Proxy Mesh When Saving A Map

When on, refines proxy meshes to static meshes when a map is saved

Refine Proxy Mesh On PIE (Play In Editor)

When on, refines proxy meshes to static meshes before starting a play in editor session

Note

Play In Editor generally saves the current level. It will likely triggger auto refinement if the Refine Proxy Mesh on PIE is disabled and Refine Refine Proxy Mesh When Saving a Map is enabled.

Generated Static Mesh Settings

This section allows you to specify some of the default Static Mesh Settings options that will be set by Houdini Engine when generating meshes. These settings are linked to the standard Unreal static mesh options. You can also change settings per asset in the Houdini Generated Static Mesh section in the details panel of a Houdini Asset, or in the details generic property attributes.

Static Mesh Build Settings

This section lists settings for the Unreal Mesh import settings when you build a static mesh.

You can also override these values per asset in the Houdini Asset options.

Setting

Description

Use Full Precision UVs

When on, UV coordinates are stored at full floatimg point precision

Source Lightmap Index

Set the source UV set index for generated lightmaps

Destination Lightmap Index

Set the destination UV set index for generated lightmaps

Min Lightmap Resolution

Set the minimum lightmap resolution for generated lightmaps

Remove Degenerates

When on, removes degenerate triangles on statich meshes

Generate Lightmap UVs

Set the option to generate Lightmap UVs when you import an HDA.

Always - Always generate Lightmap UVs

Only if missing - Only generate Lightmap UVs if they're missing in the Houdini asset’s output

Never - Never generate Lightmap UVs

Recompute Normals

Set the option to recompute normals when you import an HDA.

Always - Always recompute normals

Only if missing - Only recompute normals if they're missing in the Houdini asset’s output

Never - Never recompute normals

Recompute Tangents

Set the option to recompute tangents when you import an HDA

Always - Always recompute tangents

Only if missing - Only recompute tangents if they're missing in the Houdini asset’s output

Never - Never recompute tangents

Generate Using MikkT Space

When on, tangents and normals are recomputed using MikkT Space. This required properly laid out UVs

See the Mikkt Space documentation for more information

Build Adjacency Buffer

This is required for PNT tessellation. It can be slow and recommended to turn off for larger meshes

Compute Weighted Normals

When on, uses the surface area and corner angle of the triangles as a ratio to compute the normals

Build Reversed Index Buffer

This is required to optimize mesh in mirrored transform. Doubles the index buffer size

Use High Precision Tangent Basis

When on, tangents are stored at 16 bit instead of 8 bit

Distance Field Resolution Scale

Set the scale of the mesh when you allocate the distance field volume texture. The default scale is 1 when the mesh is placed unscaled in the world

Two-Sided Distance Field Generation

When on, generates the distance field and treats every triangle as front facing. This prevents discarding the distance field but also lowers the Distance Field AO quality

Enable Physical Material Mask

When on, enables the physical material mask

PDG Settings

Setting

Description

Async Importer Enabled

When on, enables PDG Asset link to use the asynchronous importer by default when you import work item into Unreal

Legacy

This section lists settings to control Houdini Engine for Unreal plugin when you upgrade a project using Version 1 to Version 2.

Setting

Description

Enable backward compatibilty with Version 1

When on, converts Version 1 objects and classes saved in the levels to their Version 2 equivalents. Some of these include components, parameters, inputs, and outputs.

When off, legacy objects are ignored when loading the level.

Automatically rebuild legacy Houdini Asset Components

When on, Version 1 assets get automatically rebuilt after they're converted to Version 2.

This ensures some new properties that are only in Version 2 are properly initialized and Version 1 data is cleaned up.

Houdini Location

This section lists settings to set the custom loucation for Houdini. Houdini Engine for Unreal may automatically detect the correct version and you don’t have to set them.

If you have an issue with Houdini Engine for Unreal connecting to the wrong Houdini version, see Installing Houdini Engine for Unreal troubleshooting for more information.

Setting

Description

Use custom Houdini location

When on, enables you to set a custom location for Houdini’s location

Custom Houdini location

Sets the path for the Houdini location. This must point to the directory of the HAPI library.

The default path is \Side Effects Software\Houdini X.Y.Z\bin

Houdini Executable

Set your Houdini license type

Custom Houdini Home location

Set your custom Houdini installation path.

Inputs

These settings cover the parameter used when initalizing the Houdini Engine API, HAPI.

Setting

Description

Enable the Reference Counted Input System

look at troublshooting installation

Houdini Tools

Setting

Description

Houdini Tools Search Path

A list of paths in the Unreal project where HoudiniTools panel will search for HoudiniToolsPackage assets. See Package Search Paths for more detailed information.

Houdini Engine Initialization

This section lists settings to initalize Houdini Engine API (HAPI).

Setting

Description

Cooking Thread Stack Size

Sets the stack size of the cooking thread. The value is in bytes

For Houdini’s default, set the stack size to -1

Houdini Environment Files

Set environment variables when you run Houdini Engine. These are added after the default in the houdini.env file and overwrites the process' environment variable values.

For windows, separate environment variables using ;

For Linux and Mac, separate environment variables using :

See Environment Variables for more information.

OTL Search Path

Enter the directory for your OTLs. You can use NULL to use the default Houdini OTL search paths.

For windows, separate multiple paths using ;

For Linux and Mac, separate multiple paths using :

DSO Search Path

Enter the directory for your generic DSOs (custom plugins). You can use NULL to use the default Houdini DSO search paths.

For windows, separate multiple paths using ;

For Linux and Mac, separate multiple paths using :

Image DSO Search Path

Enter the directory for your image DSOs (custom plugins). You can use NULL to use the default Houdini DSO search paths.

For windows, separate multiple paths using ;

For Linux and Mac, separate multiple paths using :

Audio DSO Search Path

Enter the directory for your audio DSOs (custom plugins). You can use NULL to use the default Houdini DSO search paths.

For windows, separate multiple paths using ;

For Linux and Mac, separate multiple paths using :

Plugin Information

This section gives information about your Houdini Engine for Unreal and Houdini versions.

Note

The Built against and Running against versions must match for the plugin to work properly.

Setting

Description

Built against Houdini

Shows the Houdini version the plugin is attempting to connect with

Built against Houdini Engine

Shows the version of Houdini Engine the plugin is attempting to connect with

Running against Houdini

Shows the version of Houdini the plugin has found

Running against Houdini Engine

Shows the version of Houdini Engine the plugin has found

Location of libHAPIL.dll

Shows the current path of the HAPI library

Acquired License Type

Shows the current license acquired by the plugin. The plugin only acquires a license when instantiating or modifying an HDA.

An Unknown license type indicates a Houdini Engine session hasn’t been started yet.

Unreal

Getting started

Basics

Using Houdini Engine

Reference

Houdini Engine for Unreal Engine is a plug-in that allows integration of Houdini technology into Unreal. Session Sync and Node Sync are two features of the Houdini Engine Plugin to interact with a live session of Houdini.

This plug-in brings Houdini’s powerful and flexible procedural workflow into Unreal Engine through Houdini Digital Assets. Artists can interactively adjust asset parameters inside the editor and use Unreal assets as inputs. Houdini’s procedural engine will then “cook” the asset and the results will be available in the editor without the need for baking.

General information:

Compatibility:

Currently, the plugins has binaries that have been built for UE5.3, 5.2, 5.1, 5.0, UE4.27 and UE4.26, and is linked with the latest production build of Houdini.

Source code for the plugin is available on this repository for UE5.3, 5.2, 5.1, 5.0, UE4.27, UE4.26.

Note

UE5.1 and UE5.0 use the same source files/branches, the 5.0 sources are also intended to be used with 5.1.

Support and reporting bugs:

SessionSync

The Houdini Engine SessionSync feature allows you to connect to a session of Houdini Engine running inside Houdini with its GUI. It supports all the features of the regular Houdini Engine workflow and additional features specific to Session Sync.

Houdini Engine uses a non-UI version of Houdini while Session Sync lets you see and interact with the Houdini session through Houdini’s user interface. It also synchronizes changes made in either Unreal or Houdini so both programs can make changes and see the same results.

NodeSync

NodeSync is a feature for the Houdini Unreal Engine Plugin that enables sharing assets between Unreal and Houdini Session Sync. It works for Skeletal and static meshes.

You can send and receive data to and from Unreal without a dedicated HDA. It works with Static and Skeletal meshes as well as Actors.

Houdini Niagara

The Houdini-Niagara plugin allows you to exchange point cloud data between Houdini and Unreal’s Niagara system using the HoudiniNiagara Data Interface. You can export Houdini’s attribute data as HoudiniPointCache assets. These can then be imported into Unreal to use the Niagara systems and emitters to create complex effects and particle systems.