# How to efficiently update InstancedStaticMesh in C++

**URL:** <https://forums.unrealengine.com/t/how-to-efficiently-update-instancedstaticmesh-in-c/469827>\
**Category:** C++\
**Tags:** unreal-engine, instancing, CPP, question\
**Created:** [August 19, 2020, 6:02am UTC](https://forums.unrealengine.com/t/how-to-efficiently-update-instancedstaticmesh-in-c/469827 "2020-08-19T06:02:45Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Eths](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Eths](https://forums.unrealengine.com/u/Eths)\
**Post date:** [August 19, 2020, 6:02am UTC](https://forums.unrealengine.com/t/how-to-efficiently-update-instancedstaticmesh-in-c/469827/1 "2020-08-19T06:02:45Z")

</div>

I am trying to create a set of instanced objects in Unreal and update their locations and color each frame. I have not coded (looked into how to do) the color modification yet. _Tips on changing color would be helpful._

The below code demonstrates creating a set of instances and modifying their location each frame, but the amount of memory read and manipulated seems excessive for only needing to change the location (transform). _The updated location data will come from sources external to unreal so it can be assumed that there is an array of float3 with new locations each frame._

**What would be the most efficient way to update instance locations each frame?**

\*\*Is there a way to change the rendered count, rendering all or a subset of the instances each frame? \*\*  
Such as rendering all one frame then the first 70% the next frame, and so on.

**Also the same should work with UHierarchicalInstancedStaticMeshComponent?**

(I am trying to port my scientific partial simulation visualization from DirectX12 to Unreal. Typical particle counts are 20k to 500k.)

`
	From header file
```
virtual void Tick(float DeltaTime) override;

UPROPERTY(EditAnywhere, BlueprintReadWrite)
//UPROPERTY(VisibleDefaultsOnly)
UInstancedStaticMeshComponent* MeshInstances;

float Increment = 0.0f;

```
``
	From cpp file
```
void AInstMeshActor::BeginPlay()
{
	Super::BeginPlay();

	for (int32 y = 0; y < 20; y++) {
		for (int32 x = 0; x < 20; x++) {
			FTransform Trans;
			FVector Spawn(x * 10.0f - 100.0f, y * 10.0f - 100.0f, 20.0f);
			FVector Scale(0.08f, 0.08f, 0.08f);
			Trans.SetLocation(Spawn);
			Trans.SetScale3D(Scale);
			MeshInstances->AddInstance(Trans);
		}
	}
}

void AInstMeshActor::Tick(float DeltaTime)
{
	Super::Tick(DeltaTime);

	for (int32 i = 0; i < MeshInstances->GetInstanceCount(); i++) {
	
		// Only for making this test
		// ** In future there will be a data source with updated locations
		FTransform Trans;
		MeshInstances->GetInstanceTransform(i, Trans, false);
		FVector Spawn = Trans.GetLocation();
		Spawn.Z = 10.0f + cos(Increment) * 10.0f;
		Trans.SetLocation(Spawn);

		// Is there a way to update location without touching as much data
		// ** FTransform is 3 vectors and I only need to modify one
		// ** Something like using memcpy to update instance locations would be nice

		if(i < MeshInstances->GetInstanceCount() - 1)
			MeshInstances->UpdateInstanceTransform(i, Trans, false, false, true);
		else
			MeshInstances->UpdateInstanceTransform(i, Trans, false, true, true);
	}

	Increment += 0.01f;
}

```
`