Welcome to the repository for the Houdini Engine For Unreal Plugin.
This plug-in is the completely remaster of the official Houdini Engine For Unreal from zero, with similar usages but up to 2x - 15x faster data I/O performance compare to the latest official plug-in, native World-Partition support, Copernicus texture I/O support, and much more functionalities optimized for making procedural landscape and city toolset. Moreover, this plug-in provides a set of C++ API to define your own unreal classes and assets I/O translators (See HoudiniPCGTranslator and HoudiniMassTranslator)
As the usage is similar, Official Document is also available for this plug-in. But there are still a lot of things are different. For the concrete usage of this plug-in, please see Document (Usage Brief) and Document (Reference) below, also see Resources/houdini/otls/examples and Source/HoudiniEngine/Public/HoudiniEngineCommon.h (All attributes, groups and parameter-tags are listed here)
See what can be achieved by Only using your HDAs and this custom HoudiniEngineForUnreal plugin: City toolchains and Terrain toolchains
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Support all builds of Houdini 20.5, Unreal Engine >= 5.4 and legacy version for 5.3.
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Support Windows, macOS-arm64(Apple Silicon M series).
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Support Editor Packaging (Debug Info binaries has been uploaded in Releases separately).
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NOT compatible with official plug-in, and can NOT work together with official one.
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In this GitHub repository, click Releases on the right side.
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Download the Houdini Engine zip file that matches your platform and Unreal Engine Version.
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Extract the HoudiniEngine folder to the Plugins of your Unreal Project Directory.
e.g.
C:/Unreal Projects/MyGameProject/Plugins/HoudiniEngine
This plug-in will automatically find the correct houdini version on your computer, or you could specify a custom Houdini installation in the plug-in settings(Houdini Engine menu/Settings).
N.B. But for Steam Houdini Indie, You MUST specify your steam houdini location manually, by plug-in setting: CustomHoudiniLocation, or use "HAPI_PATH" environment variable to specify your Houdini location.
All official functionalities are supported by this plug-in!
Here's a list of Extra functionalities than official plug-in:
N.B. This list is NOT completed, for details please see Source/HoudiniEngine/Public/HoudiniEngineCommon.h (All attributes, groups and parameter-tags are listed here) and Resources/houdini/otls/examples
Common:
- Native UE5-World-Partition & Game Packaging support, NO need bake! NO need delete houdini actor when packaging! Just using i@unreal_split_actors = 1, to generate standalone actors that can directly package to game. With s@unreal_split_attr to split actors, provides native support for world-partition actor streaming (unreal OFPA One-File-Per-Actor), See he_example_split_actors.hda.
- Streamlined Blueprint API.
- Finite state machine for achieving rich user interactions by only using HDA (See he_example_quick_shape.hda)
- Provides a set of C++ API, allow writing custom I/O translators for your own unreal classes or assets See Source/HoudiniEngine/Public/HoudiniInput.h and Source/HoudiniEngine/Public/HoudiniOutput.h. Also see HoudiniPCGTranslator and HoudiniMassTranslator of how to use these API.
- Light weight, compact usage and panel widgets.
- ... (And Much More)
Parameter:
- Much more robust nested parameter support.
- All parameters support revert, including ramps.
- All parameters support copy and paste.
- Fully Menu support, support menu script (dynamic menu), support "normal", "replace", "toggle" menu types.
- Node preset(including parameters and inputs) now save as DataTable, which can be fetched by houdini input directly.
- "unreal_ref_filter" tag for string-parameter with tag { "unreal_ref" : "1"/"2" }.
- Be careful: { "unreal_ref" : "1" } tag but on operator-path-parameter means "import as reference", which will Not actually import geometry but import references only (See HoudiniEngineCommon.h Line 369). So Remove "unreal_ref" or Set { "unreal_ref" : "0" } on operator-path-parameter if you want to import landscape layer data or mesh geometries.
- Import asset info(like Bounds of StaticMesh) by using parameter tag { "unreal_ref" : "2" / "import_info" } on string-parameter, the string value will be like:
/Script/Engine.StaticMesh'/Engine/BasicShapes/Cone.Cone';bounds:-0.5,0.5,-0.5,0.5,-0.5,0.5, #include <houdini_engine_utils.h> and use get_asset_bounds vex function to parse. - ... (And Much More)
Input:
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Much more intuitive way to draw input curves (press Enter to end/start, Click in viewport to draw points), support fuse/split points and join/detach curves, support free-hand (Shift pressing) curve drawing, also could use he_convert_curves Sop in your HDA to resample input curves.
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Custom attributes on input curves by parameter panel (Attach parms to the folder named [input name] + "_prim_attribs"/"point_attribs" to define custom per curve/point attributes. See he_example_spline_mesh_output.hda)
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Support Landscape Mask brush input with mask types of Bit, Weight, and Byte (See he_example_byte_mask.hda).
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Landscape layers input could be specified for individual editlayer and layer by input settings or parm tags (e.g. { "unreal_landscape_editlayer_Flat Middle" : "height Alpha Grass" }, { "unreal_landscape_editlayer_Base Landscape" : "* ^Alpha ^Mud ^Rock" }, { "landscape_layer" : "height" } (will import combined layer), See HoudiniEngineCommon.h Line 384)
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Landscape visibility layer now input as "Alpha", should look identical in unreal and houdini.
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Landscape layers input support update while brushing.
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Unreal spline input support import custom properties on your Blueprint.
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Texture input support, See he_example_terrain_stamp.hda. Allow HDA working with Copernicus.
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DataAsset input support.
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DynamicMeshComponent input support.
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All component types input support.
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StaticMesh and SkeletalMesh(KineFX) input using nanite fallback mesh(render data) by default, use parameter tag: { "import_render_data" : "0" } to import source model, or set on input ui panel.
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StaticMesh and SkeletalMesh(KineFX) inputs are packed before transform, #include <houdini_engine_utils.h> and use crack_packed_transform vex function to retrieve p@rot and v@scale from packed meshes.
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World Input(Actor Input) support filter all actors in current level by Label, Class, FolderPath or Tags, using parameter tag { "unreal_actor_filter_method" : "class"/"label"/"tag"/"folder" } to specify filter method, { "unreal_ref_class" : "StaticMeshActor PointLight" } to specify filter classes when filter method is "Class", using { "unreal_ref_filter" : "Tree ^Street" } to specify filter string when using other actor filter methods. Also could set on input ui panel.
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Also support filter input components by { "unreal_ref_class" : "PCGComponent StaticMeshComponent" } when World Input (Actor Input).
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All settings in the houdini input ui panel could be set by parameter tags (e.g. { "check_changed", "0" }, { "unreal_ref", "1" }(Means
import-as-reference), { "import_render_data", "0" } for individual operator path input, Rather than set all in plugin settings in official plugin. See HoudiniEngineCommon.h Line 369). -
All Input types support shared memory data transport, up to 15x faster than official shared memory session.
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... (And Much More)
Output:
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Mesh output as StaticMesh by default, rather than preview mesh(HoudiniMesh). Use s@unreal_output_mesh_type = "dynamic" to output proxy mesh (GeometryScript/DynamicMesh Output), which is way much faster than StaticMesh output.
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Mesh output support using s@unreal_split_attr (like instancer output, See he_example_split_actors.hda)
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All output types support partial update, including meshes, instancers, landscapes, geometry collection (chaos), curves using i@partial_output_mode, See HoudiniEngineCommon.h Line 249, Must split output using s@unreal_split_attr before partial update.
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All output support generated to the split actors (i@unreal_split_actors = 1) rather than attach to parent Houdini Actors (use s@unreal_split_attr specified attribute to name the split actors), and could set these split actors' properties by unreal_uproperty_* attributes (e.g. s[]@unreal_uproperty_DataLayerAssets, s@unreal_uproperty_RuntimeGrid, s@unreal_uproperty_HLODLayer), which means you could begin play in editor directly without baking output in a World-Partition level.
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So Baking is deprecated, use i@unreal_split_actors = 1 instead (See he_example_split_actors.hda).
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unreal_uproperty_* support dict and array attributes, almost everything could be set.
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Support Texture output (volumevisualmode = "image", and as an HAPI bug, MUST add my sharedmemory_volumeoutput Sop to your HDA, See he_example_texture_output.hda), optionally using s@unreal_object_path to specify output texture asset path, allow HDA working with Copernicus.
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"Alpha" heightfield layer now output as Landscape visibility layer, should look identical in houdini and unreal.
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Landscape output recommend to use shared memory output (6x faster than official plugin, add my sharedmemory_volumeoutput Sop to your HDA on the top of output node at last, See he_example_terrain_stamp.hda. Since HAPI_GetHeightFieldData has serious bugs, especially when transport volumes with various resolutions).
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Support Delete landscape EditLayer (i@unreal_landscape_editlayer_clear = 2) and Delete weight layer (i@unreal_landscape_layer_clear = 2).
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Support instantiate USceneComponent derived Classes(e.g. SplineMeshComponent, PointLightComponent etc. See he_example_spline_mesh_output.hda).
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Geometry Collection (Chaos) output as instancers (s@unreal_output_instance_type = "GC"), all of the settings on UGeometryCollection could be set by unreal_uproperty_*, rather than specific attributes in official plugin, also support split and partial output (See he_example_chaos_geometry_collection_output.hda).
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Standalone MaterialInstance asset output (Still using s@unreal_material_instance and @unreal_material_parameter_*, but on points, See he_example_vdb_output.hda)
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Unreal spline output support specify tangents (v@unreal_spline_point_arrive_tangent, v@unreal_spline_point_leave_tangent) and spline class (s@unreal_output_spline_class, can be "WaterBodyLake", "/Game/Blueprints/BP_Spline", "CineSplineComponent", etc. See he_example_spline_output.hda with "Water" plugin enabled).
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All assets (including DataAsset) support create or modify by HDA output (See he_example_split_actors.hda, using s@unreal_object_path ("having class prefix" means create, otherwise, means modify), d@unreal_object_metadata, @unreal_uproperty_*).
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Allow output specific mesh and curves that could edit directly in unreal editor (See he_example_quick_shape.hda)
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Static/AnimatedSparseVolumeTexture (VDBs) output support.
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... (And Much More)
Basic attributes are identical to official plugin, such as s@unreal_material, s@unreal_material_instance, s@unreal_instance, s@unreal_split_attr, @unreal_uproperty_, @unreal_material_parameter_, @unreal_data_table_, i@unreal_landscape_output_mode, s@unreal_landscape_editlayer_name, i@unreal_landscape_editlayer_subtractive, p@rot, v@scale, etc.
Beware that All attributes used for baking are deprecated and removed. Instead, you could use i@unreal_split_actors = 1 and @unreal_uproperty_ to set them directly without baking, to package the generated result to your game.
Beware that all attributes used for Geometry Collection output are deprecated and removed. Instead, all settings on Geometry Collection could be set by @unreal_uproperty_*.
Here're the lists of Extra attributes, groups, and parameter tags that official plugin does NOT have.
N.B. This list is NOT completed, for details please see Source/HoudiniEngine/Public/HoudiniEngineCommon.h (All attributes, groups and parameter-tags are listed here)
| Attributes | Class | Type | Explanation |
|---|---|---|---|
| unreal_split_actors | vertex/point/prim/detail | int | (Output) To generate standalone split actors rather than attach to parent houdini actors, for world-partition (OFPA) and game packaging, See he_example_split_actors.hda. |
| unreal_output_mesh_type | vertex/point/prim/detail | int/string | (Output) Define the output mesh to generate as StaticMesh(default)/DynamicMesh(= 1)/HoudiniMesh(= 2). |
| unreal_output_instance_type | vertex/point/prim/detail | int/string | (Output) Define the output points to generate as auto/ISMC(= 1)/HISMC(= 2)/Components/Actors(= 4)/Foliage(= 5)/Geometry Collection(Chaos, = 6), See he_example_chaos_geometry_collection_output.hda. |
| unreal_object_path | point/prim | string | (Input/Output) assign the path of output Texture, output Mesh, output DataTable... If on points output, means asset create/modify (e.g. = /Script/Engine.DataLayerAsset'/Game/Maps/DL_HE_Runtime.DL_HE_Runtime' will create a DataLayerAsset named DL_HE_Runtime, See he_example_split_actors.hda). |
| unreal_object_metadata | point | dict | (Input/Output) |
| unreal_output_spline_class | vertex/point/prim/detail | string | (Output) Define the output curve to generate as custom Actors or Components (e.g. /Game/BPs/BP_Spline, WaterLakeBody, HoudiniCurvesComponent, CineSplineComponent, See he_example_spline_output.hda with "Water" plugin enabled). |
| curve_type | vertex/point/prim/detail | int/string | (Input/Output) Define the HoudiniCurve/UnrealSpline type. |
| curve_closed | vertex/point/prim/detail | int | (Input/Output) Whether the HoudiniCurve/UnrealSpline is open(= 0)/closed(= 1). |
| unreal_spline_point_arrive_tangent | point | vector3 | (Input/Output) Define the arrive tangent on unreal SplineComponent, See he_example_spline_output.hda. |
| unreal_spline_point_leave_tangent | point | vector3 | (Input/Output) Define the leave tangent on unreal SplineComponent, See he_example_spline_output.hda. |
| id | point&prim | int | (Input) always >= 1, Unique id on input curves and input curve points. |
| unreal_landscape_spline_tangent_length | vertex | float | (Input) Define the length of tangents on unreal landscape splines. |
| unreal_actor_outliner_path | point | string | (Input) For World input(Actor input), difference from s@unreal_actor_path, this attribute records the path in unreal world outliner, also includes actor label |
| unreal_brush_type | point | string | (Input) For World input(BSP Actor input), == 1 means "Add", == 2 "Subtract", See EBrushType. |
| partial_output_mode | vertex/point/prim/detail | int/string | (Output) use with s@unreal_split_attr, allow incremental generated result update, = 1 means modify/create split values' output, = 2 means delete split values's output. |
| unreal_landscape_layer_clear | vertex/point/prim/detail | int/string | (Output) = 1 means clear a landscape height/weight layer, = 2 means delete weight layer |
| unreal_landscape_hole_material | vertex/point/prim/detail | string | (Input/Output) Assign landscape hole material |
| unreal_landscape_hole_material_instance | vertex/point/prim/detail | string | (Output) Create a material instance and assign this landscape hole material instance. |
| unreal_uproperty_Materials | vertex/point/prim/detail | string-array/string | (Output) Assign override materials on all PrimitiveComponents, like InstancedStaticMeshComponent, HeterogeneousVolumeComponent, See he_example_split_actors.hda and he_example_vdb_output.hda. |
| unreal_uproperty_AggGeom | vertex/point/prim/detail | dict | (Output) Assign simple collision proxies on StaticMesh, e.g. = { "SphereElems": [{"Center": {"X": 0.1, "Y": "0.2", "Z": 0.0}, "Radius": 1.1 }]} |
| delta_info | prim | string | (Input) Allow HDA to know the changes, See he_example_quick_shape.hda. |
__shared_memory_path__ |
prim | string | (Output) Warning: Must be created by sharedmemory_volumeoutput Sop to accelerate landscape output and enable copernicus texture output, do NOT create it manually! See he_example_terrain_stamp.hda and he_example_kinefx_output.hda |
| ... (And Much More) |
| Groups | Class | Explaination |
|---|---|---|
| collision_geo | prim | (Input/Output) To separate complex collision mesh from StaticMesh output. Moreover, mesh output support split by s@unreal_split_attr just like instancer output (official feature), rather than using groups to split. |
| lod_* | prim | (Input/Output) official features. |
| changed | point&prim | (Input) on input curves and input curve points, mark current operation changed elements. |
| Parameter Name Suffix | Parm Type | Explanation |
|---|---|---|
| *_point_attribs | folder | On folder parms, is [curve input name/group name] + "_point_attribs", to define custom per point attributes, See he_example_spline_mesh_output.hda. |
| *_prim_attribs | folder | On folder parms, is [curve input name/group name] + "_prim_attribs", to define custom per prim/curve attributes, See he_example_terrain_stamp.hda and he_example_quick_shape.hda. |
| *_byte_value# | int | For Mask Input and mask type = "byte", this suffix should add to multi-parm instance, See he_example_byte_mask.hda. |
| Parameter Tags | Parm Type | Explanation |
|---|---|---|
| unreal_ref | string, string-with-menu | Display a string parameter as Unreal Asset Slot, = "2"/"import_info" will import extra info of the assets, such as bounds of the StaticMesh, etc. |
| unreal_ref_class | string, operator-path | Filter asset list by classes, e.g. = "Blueprint Texture2D MaterialInterface ^MaterialInstance". |
| unreal_ref_filter | string, operator-path | Filter asset list by string, e.g. = "tree ^street". |
| unreal_ref | operator-path | = 1 to set "import as reference", meshes will import as points, landscape will import as empty volume that matches the landscape, also set on input ui panel. |
| check_changed | operator-path | Set appressive input update import, default is true, set to "0" to defer input update import. also on input ui panel. |
| num_input_objects | operator-path | (Content Input) Default can import multiple objects to one single input, set to a number to limit the count of the input objects in one single input. |
| import_render_data | operator-path | (Mesh Input) Default will import nanite fallback mesh, set to "0" to import source model (Mesh Description). |
| lod_import_method | operator-path | (Mesh Input) Import FirstLOD(= 0)/LastLOD(= 1)/AllLODs(= 2), also on input ui panel. |
| collision_import_method | operator-path | (Mesh Input) Import NoCollsion(= 0)/ImportWithMesh(= 1)/ImportCollisionOnly(= 2). |
| import_landscape_splines | operator-path | (Landscape Input) Set to "1" to import landscape with landscape splines. |
| landscape_layer | operator-path | (Landscape Input) Combine all EditLayers to import, use this tag's value to specify the layer you want to import, e.g. = "height Alpha Grass", See he_example_byte_mask.hda. |
| unreal_landscape_editlayer_* | operator-path | (Landscape Input) "unreal_landscape_editlayer_" + [EditLayer Name], like "unreal_landscape_editlayer_Base Landscape", set tag value like "landscape_layer" tag, e.g. "* ^Alpha ^Mud". |
| curve_color | operator-path | (Curve Input) Specify input curve color, e.g. "0.9, 0.4, 0.5" is pink. |
| import_rot_and_scale | operator-path | (Spline/Curve Input) import p@rot and v@scale point attributes. |
| import_collision_info | operator-path | (Curve Input) import collided actor object name and collider normal attributes. |
| unreal_actor_filter_method | operator-path | (World/Actor Input) Filter all actors in current level by Selection(default)/Class(= 1)/Label(= 2)/Tag(= 3)/Folder(= 4). |
| mask_type | operator-path | (Mask Input) Set Mask Input mask type to Bit(default)/Weight(= 1)/Byte(= 2). |
| Environment Variables | Explanation |
|---|---|
| HAPI_CLIENT | == "unreal". |
| CLIENT_PROJECT_DIR | Allow HDA to get the current unreal project directory. |
| CLIENT_SCENE_PATH | Allow HDA to get the current unreal level(map) path. |
| HOUDINI_ENGINE_FOLDER | Default is "/Game/HoudiniEngine/". |
HoudiniNode::
- static AHoudiniNode*
InstantiateHoudiniAsset(const UObject* WorldContextObject, UHoudiniAsset* HoudiniAsset) - void
LoadParameterPreset(const UDataTable* ParameterPreset) - void
SetParameterValues(const TMap<FName, FHoudiniGenericParameter>& Parameters) - void
SetCookOnParameterChanged(const bool bInCookOnParameterChanged) - void
SetCookOnUpstreamChanged(const bool bInCookOnUpstreamChanged) - FString
GetCookFolderPath() const - FString
GetBakeFolderPath() const - void
ForceCook() - void
RequestRebuild() - void
RequestPDGCook(const int32 TopNodeIdx) - AActor*
Bake() - void
BroadcastEvent(const EHoudiniNodeEvent NodeEvent) - UHoudiniInput*
GetInputByName(const FString& Name, const bool bIsOperatorPathParameter = true) const - FHoudiniGenericParameter
GetParameterValue(const FString& ParameterName) const - DELEGATE_OneParam(FHoudiniNodeEvents, const EHoudiniNodeEvent, InNodeEvent)
HoudiniNodeEvents; - ...(And Much More)
HoudiniInput::
- void
Import(UObject* Object) - ...(And Much More)
HoudiniMeshComponent::
- UStaticMesh*
SaveToStaticMesh(const FString& StaticMeshName)