UE4.26 ISM FP32 support

ISM.patch

---
 .../Components/InstancedStaticMeshComponent.h       |  5 +++++
 .../Runtime/Engine/Private/InstancedStaticMesh.cpp  | 13 +++++++++++--
 .../Runtime/Engine/Public/StaticMeshResources.h     |  3 ++-
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/Engine/Source/Runtime/Engine/Classes/Components/InstancedStaticMeshComponent.h b/Engine/Source/Runtime/Engine/Classes/Components/InstancedStaticMeshComponent.h
index d6694d8ce..af60349c1 100644
--- a/Engine/Source/Runtime/Engine/Classes/Components/InstancedStaticMeshComponent.h
+++ b/Engine/Source/Runtime/Engine/Classes/Components/InstancedStaticMeshComponent.h
@@ -133,6 +133,11 @@ class ENGINE_API UInstancedStaticMeshComponent : public UStaticMeshComponent
 	UPROPERTY(EditAnywhere, SkipSerialization, DisplayName="Instances", Category=Instances, meta=(MakeEditWidget=true, EditFixedOrder))
 	TArray<FInstancedStaticMeshInstanceData> PerInstanceSMData;
 
+	// ++
+	UPROPERTY(EditAnywhere, Category=Instances, AdvancedDisplay)
+	bool bUseFP32Transformation;
+	// --
+	
 	/** Defines the number of floats that will be available per instance for custom data */
 	UPROPERTY(EditAnywhere, Category=Instances, AdvancedDisplay)
 	int32 NumCustomDataFloats;
diff --git a/Engine/Source/Runtime/Engine/Private/InstancedStaticMesh.cpp b/Engine/Source/Runtime/Engine/Private/InstancedStaticMesh.cpp
index 9397bb3d4..e34745048 100644
--- a/Engine/Source/Runtime/Engine/Private/InstancedStaticMesh.cpp
+++ b/Engine/Source/Runtime/Engine/Private/InstancedStaticMesh.cpp
@@ -1388,6 +1388,7 @@ UInstancedStaticMeshComponent::UInstancedStaticMeshComponent(const FObjectInitia
 	BodyInstance.bSimulatePhysics = false;
 
 	bDisallowMeshPaintPerInstance = true;
+	bUseFP32Transformation = false; //++ 
 }
 
 UInstancedStaticMeshComponent::UInstancedStaticMeshComponent(FVTableHelper& Helper)
@@ -1484,7 +1485,7 @@ void UInstancedStaticMeshComponent::FlushInstanceUpdateCommands()
 {
 	InstanceUpdateCmdBuffer.Reset();
 
-	FStaticMeshInstanceData RenderInstanceData = FStaticMeshInstanceData(GVertexElementTypeSupport.IsSupported(VET_Half2));
+	FStaticMeshInstanceData RenderInstanceData = FStaticMeshInstanceData(GVertexElementTypeSupport.IsSupported(VET_Half2) && !bUseFP32Transformation ); // change
 	BuildRenderData(RenderInstanceData, PerInstanceRenderData->HitProxies);
 	PerInstanceRenderData->UpdateFromPreallocatedData(RenderInstanceData);
 }
@@ -2907,7 +2908,7 @@ void UInstancedStaticMeshComponent::InitPerInstanceRenderData(bool InitializeFro
 	else
 	{
 		TArray<TRefCountPtr<HHitProxy>> HitProxies;
-		FStaticMeshInstanceData InstanceBufferData = FStaticMeshInstanceData(GVertexElementTypeSupport.IsSupported(VET_Half2));
+		FStaticMeshInstanceData InstanceBufferData = FStaticMeshInstanceData(GVertexElementTypeSupport.IsSupported(VET_Half2) && !bUseFP32Transformation ); //  -change
 		
 		if (InitializeFromCurrentData)
 		{
@@ -3134,6 +3135,14 @@ void UInstancedStaticMeshComponent::PostEditChangeChainProperty(FPropertyChanged
 			InstanceUpdateCmdBuffer.Edit();
 			MarkRenderStateDirty();
 		}
+		//++
+		else if (PropertyChangedEvent.PropertyChain.GetActiveMemberNode()->GetValue()->GetFName() ==
+			"bUseFP32Transformation") 
+		{
+			InstanceUpdateCmdBuffer.Edit();
+			MarkRenderStateDirty();
+		}
+		//--
 	}
 	Super::PostEditChangeChainProperty(PropertyChangedEvent);
 }
diff --git a/Engine/Source/Runtime/Engine/Public/StaticMeshResources.h b/Engine/Source/Runtime/Engine/Public/StaticMeshResources.h
index 9957e0f60..c85c5d89b 100644
--- a/Engine/Source/Runtime/Engine/Public/StaticMeshResources.h
+++ b/Engine/Source/Runtime/Engine/Public/StaticMeshResources.h
@@ -1187,7 +1187,8 @@ public:
 	 * @param bInUseHalfFloat - true if device has support for half float in vertex arrays
 	 */
 	FStaticMeshInstanceData(bool bInUseHalfFloat)
-	:	bUseHalfFloat(PLATFORM_BUILTIN_VERTEX_HALF_FLOAT || bInUseHalfFloat)
+	// :	bUseHalfFloat(PLATFORM_BUILTIN_VERTEX_HALF_FLOAT && bInUseHalfFloat) //+ 
+	:	bUseHalfFloat(PLATFORM_BUILTIN_VERTEX_HALF_FLOAT && bInUseHalfFloat)
 	{
 		AllocateBuffers(0);
 	}
-- 
2.42.0.windows.2