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.

NodeCode (graph + properties reading/writing)

CDO: /Script/UnrealClientProtocolEditor.Default__NodeCodeEditingLibrary

Section Model

System Asset (UNiagaraSystem)

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

Standalone Script (UNiagaraScript)

ScriptUsage Values

Use these strings for ScriptUsage parameter:

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

Parameter Namespaces

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

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.