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Copy texture data between 2 UTexture2D's

I'm trying to combine the Kinect4Unreal plugin with OpenCV to do blob detection for interactive particle effects but running into some issues with getting the Kinect image into a texture I can process with OpenCV.

Kinect4Unreal doesn't have source code so its part is in Blueprint. The plugin outputs a Texture2D reference that I pass to a C++ function as a UTexture2D*. Then I followed part of the Procedural Materials tutorial ( https://wiki.unrealengine.com/Procedural_Materials ) to get the pixels of my texture which then I pass onto OpenCV and then write the result to a destination texture applied to a 2nd mesh.

The issue:
When passing the Texture2D reference from the Kinect to my C++ function all I get in the destination texture is a solid gray colour. If I pass an actual texture from the Content Library, that works and I can manipulate it with OpenCV and display the result without issues.

Some code:

 #include "OpenCVTest.h"
 #include "KinectViewer.h"
 #include "StaticMeshResources.h"
 // Use this function to update the texture rects you want to change:
 // NOTE: There is a method called UpdateTextureRegions in UTexture2D but it is compiled WITH_EDITOR and is not marked as ENGINE_API so it cannot be linked
 // from plugins.
 void UpdateTextureRegions(UTexture2D* Texture, int32 MipIndex, uint32 NumRegions, FUpdateTextureRegion2D* Regions, uint32 SrcPitch, uint32 SrcBpp, uint8* SrcData, bool bFreeData)
     if (Texture->Resource)
         struct FUpdateTextureRegionsData
             FTexture2DResource* Texture2DResource;
             int32 MipIndex;
             uint32 NumRegions;
             FUpdateTextureRegion2D* Regions;
             uint32 SrcPitch;
             uint32 SrcBpp;
             uint8* SrcData;
         FUpdateTextureRegionsData* RegionData = new FUpdateTextureRegionsData;
         RegionData->Texture2DResource = (FTexture2DResource*)Texture->Resource;
         RegionData->MipIndex = MipIndex;
         RegionData->NumRegions = NumRegions;
         RegionData->Regions = Regions;
         RegionData->SrcPitch = SrcPitch;
         RegionData->SrcBpp = SrcBpp;
         RegionData->SrcData = SrcData;
             FUpdateTextureRegionsData*, RegionData, RegionData,
             bool, bFreeData, bFreeData,
                 for (uint32 RegionIndex = 0; RegionIndex < RegionData->NumRegions; ++RegionIndex)
                     int32 CurrentFirstMip = RegionData->Texture2DResource->GetCurrentFirstMip();
                     if (RegionData->MipIndex >= CurrentFirstMip)
                             RegionData->MipIndex - CurrentFirstMip,
                             + RegionData->Regions[RegionIndex].SrcY * RegionData->SrcPitch
                             + RegionData->Regions[RegionIndex].SrcX * RegionData->SrcBpp
         if (bFreeData)
         delete RegionData;
 // Sets default values
      // Set this actor to call Tick() every frame.  You can turn this off to improve performance if you don't need it.
     PrimaryActorTick.bCanEverTick = true;
     SourceMesh = CreateDefaultSubobject<UStaticMeshComponent>(TEXT("SourceMesh"));
     RootComponent = SourceMesh;
     DestinationMesh = CreateDefaultSubobject<UStaticMeshComponent>(TEXT("DestinationMesh"));
 // Called when the game starts or when spawned
 void AKinectViewer::BeginPlay()
 void AKinectViewer::PostInitializeComponents()
 // Called every frame
 void AKinectViewer::Tick( float DeltaTime )
     Super::Tick( DeltaTime );
     UpdateTextureRegions(mDynamicTexture, 0, 1, mUpdateTextureRegion, mDataSqrtSize, (uint32)4, mDynamicColors, false);
     // If I change this to mSourceTexture I can see the Kinect image replicated on the 2nd mesh
     mDynamicMaterials[0]->SetTextureParameterValue("DestinationTexture", mDynamicTexture);
 // Called from Blueprint after the Kinect is ready and a KinectImage is available
 void AKinectViewer::SetSourceTextureReference(UTexture2D* KinectImage)
     SizeX = 512;
     SizeY = 424;
     //Convert the static material in our mesh into a dynamic one, and store it (please note that if you have more than one material that you wish to mark dynamic, do so here).
     //Create a dynamic texture with the default compression (B8G8R8A8)
     mDynamicTexture = UTexture2D::CreateTransient(SizeX, SizeY);
     //Make sure it won't be compressed
     mDynamicTexture->CompressionSettings = TextureCompressionSettings::TC_VectorDisplacementmap;
     //Turn off Gamma-correction
     mDynamicTexture->SRGB = 0;
     //Guarantee no garbage collection by adding it as a root reference
     //Update the texture with new variable values.
     mSourceTexture = KinectImage;
     //Make sure it won't be compressed
     mSourceTexture->CompressionSettings = TextureCompressionSettings::TC_VectorDisplacementmap;
     //Turn off Gamma-correction
     mSourceTexture->SRGB = 0;
     //Guarantee no garbage collection by adding it as a root reference
     //Update the texture with new variable values.
     //Grab the colorvalues from our existing texture (the one we created at '''Texture Setup''') and copy it into a uint8* mTextureColors variable.
     int32 w, h;
     w = mSourceTexture->GetSizeX();
     h = mSourceTexture->GetSizeY();
     FTexture2DMipMap& readMip = mSourceTexture->PlatformData->Mips[0];
     mDataSize = w * h * 4; // * 4 because we're working with uint8's - which are 4 bytes large
     mDataSqrtSize = w * 4; // * 4 because we're working with uint8's - which are 4 bytes large
     // Initalize our dynamic pixel array with data size
     mDynamicColors = new uint8[mDataSize];
     // Copy our current texture's colors into our dynamic colors
     FMemory::Memcpy(mDynamicColors, mTextureColors, mDataSize);
     // Create a new texture region with the width and height of our dynamic texture
     mUpdateTextureRegion = new FUpdateTextureRegion2D(0, 0, 0, 0, w, h);
     // Set the Paramater in our material to our texture
     mDynamicMaterials[0]->SetTextureParameterValue("DestinationTexture", mDynamicTexture);
 void AKinectViewer::ProcessKinectImage()
     // Some image processing tests
     //int pixelAmount = mDataSize / 4;
     //for (int i = 0; i < pixelAmount; ++i)
     //    //int blue = i * 4 + 0;
     //    //int green = i * 4 + 1;
     //    //int red = i * 4 + 2;
     //    //int alpha = i * 4 + 3;
     //    mDynamicColors[i] = 120; // Set pixel's red value to 120
     //auto thresh = cv::Mat(SizeX, SizeY, CV_8UC4, mSourceTextureColors);
     //cv::threshold(thresh, thresh, 0, 255, 3);
     //cv::erode(thresh, thresh, cv::Mat());
     //cv::dilate(thresh, thresh, cv::Mat());
     //mDynamicColors = (uint8*)thresh.data;

The result (Kinect source image on the left, C++ result on the right): alt text

Any ideas? Thanks you in advance

Product Version: UE 4.13
kinect.png (634.0 kB)
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asked Dec 07 '16 at 12:36 PM in C++ Programming

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