unreal-niagara-editing

Niagara Editing

Niagara editing uses three complementary paths: NiagaraOperationLibrary for structural operations, NodeCode for graph/property reading and writing, and ObjectOperationLibrary for detailed UObject property access.

Prerequisite: UE editor running with UCP plugin enabled.

API Overview

NiagaraOperationLibrary (structural operations)

CDO: /Script/UnrealClientProtocolEditor.Default__NiagaraOperationLibrary

UObject path parameters (System, Emitter, Script, etc.) are auto-resolved by UCP — pass the object path as a string and UCP converts it to the UObject pointer.

Function	Params	Description
AddEmitter	System(path), SourceEmitter(path), Name	Add emitter to system
RemoveEmitter	System(path), EmitterName	Remove emitter from system
ReorderEmitter	System(path), EmitterName, NewIndex	Reorder emitter
AddUserParameter	System(path), ParamName, TypeName, DefaultValue	Add User parameter
RemoveUserParameter	System(path), ParamName	Remove User parameter
AddModule	SystemOrEmitter(path), ScriptUsage, ModuleScript(path), Index	Add module to stack
RemoveModule	SystemOrEmitter(path), ScriptUsage, ModuleNodeGuid	Remove module
MoveModule	SystemOrEmitter(path), ScriptUsage, ModuleNodeGuid, NewIndex	Reorder module
SetModuleEnabled	SystemOrEmitter(path), ScriptUsage, ModuleNodeGuid, bEnabled	Enable/disable module
GetModules	SystemOrEmitter(path), ScriptUsage	List modules with name/guid/enabled/scriptPath
SetModuleInputValue	SystemOrEmitter(path), ScriptUsage, ModuleNodeGuid, InputName, Value	Set input to literal (Rapid Iteration)
SetModuleInputBinding	SystemOrEmitter(path), ScriptUsage, ModuleNodeGuid, InputName, LinkedParamName	Bind input to parameter
SetModuleInputDynamicInput	SystemOrEmitter(path), ScriptUsage, ModuleNodeGuid, InputName, DynamicInputScript(path)	Set dynamic input
ResetModuleInput	SystemOrEmitter(path), ScriptUsage, ModuleNodeGuid, InputName	Reset to default
GetModuleInputs	SystemOrEmitter(path), ScriptUsage, ModuleNodeGuid	List inputs with name/type/mode/value
AddRenderer	Emitter(path), RendererClassName	Add renderer
RemoveRenderer	Emitter(path), RendererIndex	Remove renderer
MoveRenderer	Emitter(path), RendererIndex, NewIndex	Reorder renderer
AddEventHandler	Emitter(path)	Add event handler
RemoveEventHandler	Emitter(path), UsageIdString	Remove event handler
AddSimulationStage	Emitter(path)	Add simulation stage
RemoveSimulationStage	Emitter(path), StageIdString	Remove simulation stage
MoveSimulationStage	Emitter(path), StageIdString, NewIndex	Reorder simulation stage
AddGraphParameter	Script(path), ParamName, TypeName	Add parameter to script graph
RemoveGraphParameter	Script(path), ParamName	Remove parameter
RenameGraphParameter	Script(path), OldName, NewName	Rename parameter
CreateScratchPadScript	SystemOrEmitter(path), ScriptName, Usage, ModuleUsageBitmask	Create a ScratchPad (Local Module) script

NodeCode (graph + properties reading/writing)

CDO: /Script/UnrealClientProtocolEditor.Default__NodeCodeEditingLibrary

Function	Params	Description
Outline	AssetPath	List available sections
ReadGraph	AssetPath, Section	Read section content as text
WriteGraph	AssetPath, Section, GraphText	Write section content back

Section Model

System Asset (UNiagaraSystem)

Section	Type	Description
[SystemProperties]	Properties	Warmup, bounds, determinism, scalability, LWC, render defaults
[Emitters]	Properties	Emitter list with names, enabled state, ObjectPath
[UserParameters]	Properties	User. namespace exposed parameters
[ScratchPadScripts]	Properties	Local Module scripts with name, Usage, ModuleUsageBitmask, ObjectPath
[SystemSpawn]	Graph	System spawn stage module chain
[SystemUpdate]	Graph	System update stage module chain

Emitter Object (UNiagaraEmitter, accessed via ObjectPath from [Emitters])

Section	Type	Description
[EmitterProperties]	Properties	SimTarget, bLocalSpace, bounds, allocation, inheritance
[ParticleAttributes]	Properties (read-only)	Compiled particle attributes list
[Renderers]	Properties	Renderer list with class, ObjectPath
[EventHandlers]	Properties	Event handler configs
[SimulationStages]	Properties	Simulation stage list
[EmitterSpawn]	Graph	Emitter spawn stage
[EmitterUpdate]	Graph	Emitter update stage
[ParticleSpawn]	Graph	Particle spawn stage
[ParticleUpdate]	Graph	Particle update stage
[ParticleEvent:EventId]	Graph	Event handler graph
[SimulationStage:StageId]	Graph	Custom simulation stage graph

Standalone Script (UNiagaraScript)

Section	Type	Description
[Module]	Graph	Module script graph
[Function]	Graph	Function script graph
[DynamicInput]	Graph	Dynamic input script graph

ScriptUsage Values

Use these strings for ScriptUsage parameter:

SystemSpawn, SystemUpdate, EmitterSpawn, EmitterUpdate, ParticleSpawn, ParticleUpdate, ParticleEvent, SimulationStage, Module, Function, DynamicInput

Parameter Namespaces

Namespace	Scope	Writable In
System.	System-level attributes	System stages
Emitter.	Emitter-level attributes	Emitter stages
Particles.	Particle attributes	Particle stages
Module.	Module input parameters	Module internal
User.	User-exposed parameters	Runtime settable
Engine.	Engine values (DeltaTime, etc.)	Read-only
Local.Module.	Module-local temporaries	Module internal
Transient.	Cross-module temporaries	Current stage
Constants.	Rapid iteration parameters	Editor-set values

Module Input Setting Methods

Modules can have their inputs set in four ways:

1. Literal Value (SetModuleInputValue) — stored as Rapid Iteration Parameter in Constants.EmitterName.ModuleName.InputName, no graph nodes
2. Binding (SetModuleInputBinding) — ParameterMapGet reads another parameter (e.g. User.MyParam, Emitter.SpawnRate)
3. Dynamic Input (SetModuleInputDynamicInput) — a DynamicInput script computes the value
4. Data Interface — a NiagaraNodeInput provides a data interface object
5. Default — module's built-in default, no override

Workflow

Exploring a System

// 1. Get system structure
{"object":"...NodeCodeEditingLibrary","function":"Outline","params":{"AssetPath":"/Game/FX/NS_Fountain"}}

// 2. Read emitter list
{"object":"...NodeCodeEditingLibrary","function":"ReadGraph","params":{"AssetPath":"/Game/FX/NS_Fountain","Section":"Emitters"}}

// 3. Deep-dive into an emitter (use ObjectPath from step 2)
{"object":"...NodeCodeEditingLibrary","function":"Outline","params":{"AssetPath":"/Game/FX/NS_Fountain.NS_Fountain:Fountain"}}

Modifying Module Stack

// Add a module
{"object":"...NiagaraOperationLibrary","function":"AddModule","params":{"EmitterPath":"...Fountain","ScriptUsage":"ParticleSpawn","ModuleAssetPath":"/Niagara/Modules/AddVelocity","Index":1}}

// Set module input to a value
{"object":"...NiagaraOperationLibrary","function":"SetModuleInputValue","params":{"EmitterPath":"...Fountain","ScriptUsage":"ParticleSpawn","ModuleGuid":"...","InputName":"Velocity","Value":"(X=0,Y=0,Z=100)"}}

// Bind module input to User parameter
{"object":"...NiagaraOperationLibrary","function":"SetModuleInputBinding","params":{"EmitterPath":"...Fountain","ScriptUsage":"ParticleSpawn","ModuleGuid":"...","InputName":"Velocity","LinkedParamName":"User.InitialVelocity"}}

Editing a Module Script's Internal Graph

ReadGraph("/Game/FX/Modules/MyModule", "Module")
→ Text representation of the node graph

WriteGraph("/Game/FX/Modules/MyModule", "Module", <modified text>)
→ Diff result

Modifying Renderer Properties

// Get renderer list
{"object":"...NodeCodeEditingLibrary","function":"ReadGraph","params":{"AssetPath":"...Fountain","Section":"Renderers"}}

// Read detailed renderer properties via reflection
{"object":"...ObjectOperationLibrary","function":"DescribeObject","params":{"ObjectPath":"...SpriteRenderer_0"}}

// Set renderer property
{"object":"...ObjectOperationLibrary","function":"SetObjectProperty","params":{"ObjectPath":"...SpriteRenderer_0","PropertyName":"Material","JsonValue":"\"/Game/Materials/M_Particle\""}}

Node Types in Graph Sections

Encoded Name	UClass	Description
FunctionCall:<ScriptPath>	UNiagaraNodeFunctionCall	Module/function call (asset module)
FunctionCall:ScratchPad:<Name>	UNiagaraNodeFunctionCall	ScratchPad (Local Module) reference
Assignment	UNiagaraNodeAssignment	Inline assignment
CustomHlsl	UNiagaraNodeCustomHlsl	Custom HLSL code
ParameterMapGet	UNiagaraNodeParameterMapGet	Read from parameter map
ParameterMapSet	UNiagaraNodeParameterMapSet	Write to parameter map
NiagaraOp	UNiagaraNodeOp	Math operation (OpName property)
NiagaraNodeInput	UNiagaraNodeInput	Input node
NiagaraNodeOutput	UNiagaraNodeOutput	Output node

Working with ScratchPad (Local Module) Scripts

ScratchPad scripts are inline module/function/dynamic-input scripts embedded within a System or Emitter. They appear in [ScratchPadScripts] and are referenced in graphs as FunctionCall:ScratchPad:<Name>.

// 1. Read ScratchPad list from source system
{"object":"...NodeCodeEditingLibrary","function":"ReadGraph","params":{"AssetPath":"/Game/FX/NS_Source","Section":"ScratchPadScripts"}}

// 2. Create matching ScratchPad scripts in target system
{"object":"...NiagaraOperationLibrary","function":"CreateScratchPadScript","params":{"SystemOrEmitter":"/Game/FX/NS_Target","ScriptName":"MyModule","Usage":"Module","ModuleUsageBitmask":56}}

// 3. Read source ScratchPad internal graph (use ObjectPath from step 1)
{"object":"...NodeCodeEditingLibrary","function":"ReadGraph","params":{"AssetPath":"/Game/FX/NS_Source.NS_Source:MyModule","Section":"Module"}}

// 4. Write to target ScratchPad (use ObjectPath from step 2)
{"object":"...NodeCodeEditingLibrary","function":"WriteGraph","params":{"AssetPath":"/Game/FX/NS_Target.NS_Target:MyModule","Section":"Module","GraphText":"..."}}

// 5. Now write stage graphs — FunctionCall:ScratchPad:MyModule auto-resolves to target system's script

Important Notes

• GUID Preservation: When editing graphs with WriteGraph, preserve existing node #guid values to ensure correct diff matching.
• Emitters are embedded: Emitters inside a System are copies, not references. Access them via ObjectPath from the [Emitters] section.
• ParticleAttributes are read-only: They are derived from compiled scripts. To add/remove particle attributes, add/remove modules that write to Particles. namespace.
• Prefer OperationLibrary for module stack changes: Use AddModule/RemoveModule/SetModuleInput instead of WriteGraph for System/Emitter stage graphs, as these APIs correctly handle Rapid Iteration parameters and Override node management.