- Removed Custom Data test actor, as the issue has been fixed in 4.25.

- Fixed a bug with color custom data.
- Added update functions for Points, needs to be tested.
- Fixed remove line function to correctly delete the instances, as RemoveInstance actually shrinks the ids. This is a slow operation currently.

InstancedMeshLines/Plugins/InstancedMeshLineRendering/Source/InstancedMeshLineRendering/Private/GPUInstancedLineComponent.cpp

@@ -280,7 +280,7 @@ int32 UGPUInstancedLineComponent::AddLine(const TArray<FVector>& Line, FLinearCo
 		int32 InstanceId = AddInstanceWorldSpace(FTransform::Identity);
 		SetCustomDataValue(InstanceId, 0, Color.R, false);
 		SetCustomDataValue(InstanceId, 1, Color.G, false);		
-		SetCustomDataValue(InstanceId, 2, static_cast<float>(InstanceId)/*Color.B*/, false);
+		SetCustomDataValue(InstanceId, 2, Color.B, false);
 		SetCustomDataValue(InstanceId, 3, Width, false);		
 		SetCustomDataValue(InstanceId, 4, static_cast<float>(CurrentTextureIndex), false); // Segment Start
 		NewLineArray.Add(TPair<int32, int32>{InstanceId, LinearLineData.Num() + PointIndex});
@@ -732,6 +732,7 @@ bool UGPUInstancedLineComponent::InsertPoints(int32 LineId, int32 SegmentId, con
 	return true;
 }
 
+// todo test this not sure if it actually works 
 bool UGPUInstancedLineComponent::UpdateLine(int32 LineId, TArray<FVector>& Points)
 {
 	TRACE_CPUPROFILER_EVENT_SCOPE(TEXT("UGPUInstancedLineComponent::UpdateLine"))
@@ -835,10 +836,52 @@ bool UGPUInstancedLineComponent::UpdatePoint(int32 LineId, int32 PointId, const
 	return true;
 }
 
-bool UGPUInstancedLineComponent::UpdatePoints(int32 LineId, int32 StartingPointId, const TArray<FVector>& Points)
+// todo test this not sure if it actually works 
+bool UGPUInstancedLineComponent::UpdatePoints(int32 LineId, int32 StartingPointId, TArray<FVector>& Points)
+{
+	TRACE_CPUPROFILER_EVENT_SCOPE(TEXT("UGPUInstancedLineComponent::UpdatePoints"))
+
+	const GPULineArray& Line = LineMap[LineId];
+
+	if (Line.Num() < Points.Num() || StartingPointId + Points.Num() > Line.Num())
 	{
 		return false;
 	}
+	if(Line.Num() == Points.Num() && StartingPointId == 0)
+	{
+		return UpdateLine(LineId, Points);
+	}
+
+	// Should check for validity
+	const GPULineIndices& FirstPointIndices = LineMap[LineId][StartingPointId];
+
+	TArray<FVector4>* TextureData = new TArray<FVector4>(MoveTemp(Points));
+	if(StartingPointId == 0)
+	{
+		(*TextureData)[0].W = 0;
+	}
+	if (StartingPointId + Points.Num() == Line.Num())
+	{
+		TextureData->Last().W = -1;
+	}
+	
+	const int32 StartTextureIndex = Line[StartingPointId].Value;
+	const FIntPoint StartIndex(StartTextureIndex % TextureWidth, StartTextureIndex / TextureWidth);
+
+	FMemory::Memcpy(LinearLineData.GetData() + StartTextureIndex, TextureData->GetData(), TextureData->Num() * sizeof(FVector4));
+
+	int32 NumberOfRegions = 0;
+	const FUpdateTextureRegion2D* Regions = CalculateTextureRegions(StartIndex, TextureData->Num(), NumberOfRegions);
+
+	PositionTexture->UpdateTextureRegions(0, NumberOfRegions, Regions, TextureWidth * sizeof(FVector4), sizeof(FVector4), (uint8*)TextureData->GetData(),
+		[](auto InTextureData, auto InRegions)
+	{
+		delete InTextureData;
+		delete InRegions;
+	});
+
+	return true;
+}
 
 bool UGPUInstancedLineComponent::RemoveLine(int32 LineId)
 {
@@ -848,11 +891,24 @@ bool UGPUInstancedLineComponent::RemoveLine(int32 LineId)
 	const int32 LineLength = Line.Num();
 	const int32 LineTextureIndex = Line[0].Value;
 
-	// Remove the instances first:
+	// Because ISM are so great, they reshuffle id's on removal....
+	// This means we can't just remove consecutive ids, but need to actually re-calculate them EVERY SINGLE TIME
+	// As instances of a line aren't guaranteed to be in order, collect and sort the indices first, then start top down.
+	//
+	TArray<int32> InstancesToRemove;
+	InstancesToRemove.Reserve(Line.Num());
+	
 	for(int32 PointIndex = 0; PointIndex < Line.Num() - 1; PointIndex++)
 	{
-		RemoveInstance(Line[PointIndex].Key);
+		InstancesToRemove.Add(Line[PointIndex].Key);
+	}
+	InstancesToRemove.Sort();
+
+	for (int32 Index = 0; Index < InstancesToRemove.Num(); Index++)
+	{
+		RemoveInstance(InstancesToRemove[InstancesToRemove.Num() - 1 - Index]);		
 	}
+	
 	// Remove linear data:
 	LinearLineData.RemoveAt(LineTextureIndex, LineLength);
 	// Remove line from map, this invalidates above Line reference.
@@ -862,9 +918,23 @@ bool UGPUInstancedLineComponent::RemoveLine(int32 LineId)
 	for (TPair<int32, GPULineArray>& Pair : LineMap)
 	{
 		GPULineArray& LineArray = Pair.Value;
-		if (LineArray[0].Value >= LineTextureIndex)
-		{
 		for (int32 i = 0; i < LineArray.Num(); ++i)
+		{
+			if (LineArray[i].Key >= InstancesToRemove[0])
+			{
+				// Apparently unreal also shuffles the instance indices, this might bite us later on
+
+				// This is insanely slow:
+
+				for(int32 Index = InstancesToRemove.Num(); Index > 0; --Index)
+				{
+					if (LineArray[i].Key >= InstancesToRemove[Index - 1])
+					{
+						LineArray[i].Key -= Index;
+					}
+				}								
+			}
+			if (LineArray[0].Value >= LineTextureIndex)
 			{
 				LineArray[i].Value -= LineLength;
 				SetCustomDataValue(LineArray[i].Key, 4, LineArray[i].Value, false);

InstancedMeshLines/Plugins/InstancedMeshLineRendering/Source/InstancedMeshLineRendering/Public/GPUInstancedLineComponent.h

@@ -227,7 +227,7 @@ public:
 
 	// todo
 	UFUNCTION(BlueprintCallable, Category = "Components|InstancedLineComponent")
-	bool UpdatePoints(int32 LineId, int32 StartingPointId, const TArray<FVector>& Points);
+	bool UpdatePoints(int32 LineId, int32 StartingPointId, TArray<FVector>& Points);
 
 	// Removal Functions
 	// todo