Quickstart

This walks through the minimal path to get a triangle rendering with RMC: a C++ actor that builds its own mesh. It follows the same pipeline as the plugin’s own ARealtimeMeshExample_Simple_HelloTriangle example (Source/RealtimeMeshExamples/Private/Simple/RealtimeMeshExample_Simple_HelloTriangle.cpp), so you can cross-reference the full working source at any point.

Prerequisites

You need a C++-ready Unreal project with the plugin installed (see Installation) and RealtimeMeshComponent added to your module’s Build.cs:

PublicDependencyModuleNames.Add("RealtimeMeshComponent");

1. Derive from ARealtimeMeshActor

ARealtimeMeshActor owns a URealtimeMeshComponent for you (mobility, collision profile, root component are already wired up). Create a new actor class that derives from it:

MyFirstMesh.h

#pragma once

#include "CoreMinimal.h"
#include "RealtimeMeshActor.h"
#include "MyFirstMesh.generated.h"

UCLASS()
class MYGAME_API AMyFirstMesh : public ARealtimeMeshActor
{
  GENERATED_BODY()

protected:
  virtual void OnConstruction(const FTransform& Transform) override;
};

Building the mesh in OnConstruction means it renders immediately when you drop the actor into a level or move it around in the editor — this is what every shipped example does. If your mesh generation is expensive and you don’t want it re-running on every editor drag, set bDeferGeneration = true (a property on ARealtimeMeshActor) and build the mesh in an override of OnGenerateMesh_Implementation() instead — it only fires when a rebuild is explicitly requested.

2. Initialize the mesh and build a StreamSet

In OnConstruction, initialize the component with the URealtimeMeshSimple leaf type — the general-purpose, CPU-authored mesh type, closest in behavior to ProceduralMeshComponent:

MyFirstMesh.cpp

#include "MyFirstMesh.h"
#include "RealtimeMeshSimple.h"

using namespace RealtimeMesh;

void AMyFirstMesh::OnConstruction(const FTransform& Transform)
{
  Super::OnConstruction(Transform);

  URealtimeMeshSimple* RealtimeMesh = GetRealtimeMeshComponent()->InitializeRealtimeMesh<URealtimeMeshSimple>();

  // The StreamSet holds the raw buffers: positions, tangents, texcoords, triangles, etc.
  FRealtimeMeshStreamSet StreamSet;

  // TRealtimeMeshBuilderLocal is a helper that writes into a StreamSet's buffers for you.
  // Template args: index type, tangent type, texcoord type, number of UV channels.
  TRealtimeMeshBuilderLocal<uint16, FPackedNormal, FVector2DHalf, 1> Builder(StreamSet);

  Builder.EnableTangents();
  Builder.EnableTexCoords();
  Builder.EnableColors();
  Builder.EnablePolyGroups();

  const int32 V0 = Builder.AddVertex(FVector3f(-50.0f, 0.0f, 0.0f))
    .SetNormalAndTangent(FVector3f(0.0f, -1.0f, 0.0f), FVector3f(1.0f, 0.0f, 0.0f))
    .SetColor(FColor::Red)
    .SetTexCoord(FVector2f(0.0f, 0.0f));

  const int32 V1 = Builder.AddVertex(FVector3f(0.0f, 0.0f, 100.0f))
    .SetNormalAndTangent(FVector3f(0.0f, -1.0f, 0.0f), FVector3f(1.0f, 0.0f, 0.0f))
    .SetColor(FColor::Green)
    .SetTexCoord(FVector2f(0.5f, 1.0f));

  const int32 V2 = Builder.AddVertex(FVector3f(50.0f, 0.0f, 0.0f))
    .SetNormalAndTangent(FVector3f(0.0f, -1.0f, 0.0f), FVector3f(1.0f, 0.0f, 0.0f))
    .SetColor(FColor::Blue)
    .SetTexCoord(FVector2f(1.0f, 0.0f));

  // Add the triangle, tagged into poly group 0.
  Builder.AddTriangle(V0, V1, V2, 0);

A few things worth calling out:

• RealtimeMesh:: needs to be in scope (using namespace RealtimeMesh;) for FRealtimeMeshStreamSet and the builder types.
• AddVertex returns a handle you chain .Set...() calls onto to fill in per-vertex data.
• EnablePolyGroups() lets you tag triangles so one StreamSet can back multiple sections — see Poly Groups in Key Concepts.

3. Set up materials and create the section group

Material slots are set up on the mesh object, then a section group is created from the StreamSet:

  // One material slot per poly group used above.
  RealtimeMesh->SetupMaterialSlot(0, "PrimaryMaterial");

  const FRealtimeMeshBufferSetKey GroupKey = FRealtimeMeshBufferSetKey::Create(0, FName("MyTriangle"));

  // Because the StreamSet has poly groups enabled, this auto-creates one section per poly group.
  RealtimeMesh->CreateBufferSet(GroupKey, MoveTemp(StreamSet));
}

CreateBufferSet takes the StreamSet by rvalue reference — pass it with MoveTemp (as above) or construct it in place; the section group takes ownership of the buffers rather than copying them.

At this point, compiling and placing AMyFirstMesh in a level renders a single triangle using whatever material you assign to the PrimaryMaterial slot in the actor’s details panel.

Next steps

• Key Concepts — streams, stream sets, and the builder types in more depth.
• Component Core — materials, LODs, sections, and updating mesh data after the initial build.
• Examples — every shipped example actor, from this same triangle to Nanite and spatial streaming.