Baby Steps with Spatial Mapping in 2D and 3D Using XAML and SharpDX

NB: The usual blog disclaimer for this site applies to posts around HoloLens. I am not on the HoloLens team. I have no details on HoloLens other than what is on the public web and so what I post here is just from my own experience experimenting with pieces that are publicly available and you should always check out the official developer site for the product documentation.

I’ve been living in fear and hiding from a particular set of APIs Winking smile

Ever since HoloLens and Windows Mixed Reality first came along, I’ve been curious about the realities of the spatial mapping APIs and yet I’ve largely just treated them as a “black box”.

Naturally, that’s not to say that I haven’t benefitted from those APIs because I’ve been using them for many months in Unity via the Mixed Reality Toolkit and its support for spatial mapping and the prefab that’s fairly easy to drop into a Unity project as I first explored in this post last year;

Hitchhiking the HoloToolkit-Unity, Leg 3–Spatial Understanding (& Mapping)

That said, I’ve still had it on my “to do list” for a long time to visit these APIs a little more directly and that’s what this blog post is about.

It’s important to say that the post is mostly meant to be just “for fun” to give me a place to write down some explorations – I’m not planning to do an exhaustive write up of the APIs and what I’ll end up with by the end of this post is going to be pretty “rough”.

It’s also important to say that there are official documentation pages which detail a lot more than I’m about to write up in this post.

Spatial mapping

Spatial mapping in DirectX

but (as usual) I hadn’t really read those documents in nearly enough detail until I started to explore on my own for this post – it’s the exploration that drives the learning.

Additionally, there’s a great official sample that goes along with those documents;

Holographic Spatial Mapping Sample

but, again, I hadn’t actually seen this sample until I got well into writing this post and was trying to figure things out and I realised that I was largely trying to produce a much simpler, less functional piece of code which targeted a different type of application than the one in the sample but there are many similarities between where I ended up and that sample.

So, if you want the definitive views on these topics there are lots of links to visit.

In the meantime, I’m going to write up my own experiments here.

Choosing a Sandbox to Play In

Generally speaking, if I’m wanting to experiment with some .NET APIs then I write a console application. It seems the quickest, easiest thing to spin up.

In a Mixed Reality world, the equivalent seems to be a 2D XAML application. I find it is much quicker to Code->Deploy->Test->Debug when working on a 2D XAML application than when working on (e.g.) a 3D Unity application.

Of course, the output is then a 2D app rather than an immersive app but if you just want to test out some UWP APIs (which the spatial mapping APIs are) then that’s ok.

Specifically, in this case, I found that trying to make use of these APIs in a 2D environment seemed to actually be helpful to gaining some understanding of them as it stopped me from just looking for a quick Unity solution to various challenges and I definitely felt that I wasn’t losing anything by at least starting my journey inside of a 2D XAML application where I could quickly iterate.

Getting Going – Asking for Spatial Mapping API Access

I made a quick, blank 2D XAML UWP application in Visual Studio and made sure that its application manifest gave me the capability to use Spatial Mapping.

When I look in Visual Studio today, I don’t see this listed as an option in the UI and so I hacked the manifest file in the XML editor;


where uap2 translates as a namespace to;


in case you ever got stuck on that one. From there, I had a blank app where I could write some code to run on the Loaded event of my main XAML page.

Figuring out the SurfaceSpatialObserver

At this point, I had an idea of what I wanted to do and I was fairly sure that I needed to spin up a SpatialSurfaceObserver which does a lot of the work of trying to watch surfaces as they are discovered and refined by HoloLens.

The essence of the class would seem to be to check whether spatial mapping is supported and available via the IsSupported and RequestAccessAsync() methods.

Once support is ascertained, you define some “volumes” for the observer to observe for spatial mapping data via the SetBoundingVolume/s method and then you can interrogate that data via the GetObservedSurfaces method.

Additionally, there’s an event ObservedSurfacesChanged to tell you when the data relating to surfaces has changed because the device has added/removed or updated data.

This didn’t seem too bad and so my code for checking for support ended up looking as below;

  async void OnLoaded(object sender, RoutedEventArgs e)
      bool tryInitialisation = true;

      if (Windows.Foundation.Metadata.ApiInformation.IsApiContractPresent(
          "Windows.Foundation.UniversalApiContract", 4, 0))
        tryInitialisation = SpatialSurfaceObserver.IsSupported();

      if (tryInitialisation)
        var access = await SpatialSurfaceObserver.RequestAccessAsync();

        if (access == SpatialPerceptionAccessStatus.Allowed)
          tryInitialisation = false;
      if (!tryInitialisation)
        var dialog = new MessageDialog(
          "Spatial observation is either not supported or not allowed", "Not Available");

        await dialog.ShowAsync();

Now, as far as I could tell the SpatialSurfaceObserver.IsSupported() method only became available in V4 of the UniversalApiContract so I’m trying to figure out whether it’s safe to call that API or not as you can see above before using it.

The next step would be perhaps to try and define volumes and so I ploughed ahead there…

Volumes, Coordinate Systems, Reference Frames, Locators – Oh My Winking smile

I wanted to keep things as simple as possible and so I chose to look at the SetBoundingVolume method which takes a single SpatialBoundingVolume and there are a number of ways of creating these based on Boxes, Frustrums and Spheres.

I figured that a sphere was a fairly understandable thing and so I went with a sphere and decided I’d use a 5m radius on my sphere hoping to determine all surface information within that radius.

However, to create a volume you first need a SpatialCoordinateSystem and the easiest way I found of getting hold of one of those was to get hold of a frame of reference.

Frames of reference can either be “attached” in the sense of being head-locked and following the device or they can be “stationary” where they don’t follow the device.

A stationary frame of reference seemed easier to think about and so I went that way but to get hold of a frame of reference at all I seemed to need to use a SpatialLocator which has a handy GetDefault() method on it and then I can use the CreateStationaryFrameOfReferenceAtCurrentLocation() method to create my frame.

So…my reasoning here is that I’m creating a frame of reference at the place where the app starts up and that it will never move during the app’s lifetime. Not perhaps the most “flexible” thing in the world, but it seemed simpler than any other options so I went with it.

With that in place, my “start-up” code looks as below;

  void InitialiseSurfaceObservation()
      // We want the default locator.
      this.locator = SpatialLocator.GetDefault();

      // We try to make a frame of reference that is fixed at the current position (i.e. not
      // moving with the user).
      var frameOfReference = this.locator.CreateStationaryFrameOfReferenceAtCurrentLocation();

      this.baseCoordinateSystem = frameOfReference.CoordinateSystem;

      // Make a box which is centred at the origin (the user's startup location)
      // and is hopefully oriented to the Z axis and a certain width/height.
      var boundingVolume = SpatialBoundingVolume.FromSphere(
        new SpatialBoundingSphere()
          Center = new Vector3(0, 0, 0),
          Radius = SPHERE_RADIUS
      this.surfaceObserver = new SpatialSurfaceObserver();

Ok…I have got hold of a SpatialSurfaceObserver that’s observing one volume for me defined by a sphere. What next?

Gathering and Monitoring Surfaces Over Time

Having now got my SpatialSurfaceObserver with a defined volume, I wanted some class that took on the responsibility of grabbing any surfaces from it, putting them on a list and then managing that list as the observer fired events to flag that surfaces had been added/removed/updated.

In a real application, it’s likely that you’d need to do this in a highly performant way but I’m more interested in experimentation here than performance and so I wrote a small SurfaceChangeWatcher class which I can pass the SpatialSurfaceObserver to.

Surfaces are identified by GUID and so this watcher class maintains a simple Dictionary<Guid,SpatialSurfaceInfo>. On startup, it calls the GetObservedSurfaces method to initially populate its dictionary and then it handles the ObservedSurfacesChanged event to update its dictionary as data changes over time.

It aggregates up the changes that it sees and fires its own event to tell any interested parties about the changes.

I won’t post the whole source code for the class here but will just link to it instead. It’s not too long and it’s not too complicated.

Source SurfaceChangeWatcher.cs.

Checking for Surface Data

At this point, I’ve enough code to fire up the debugger and debug my 2D app on a HoloLens or an emulator and see if I can get some spatial mapping data into my code.

It’s worth remembering that the HoloLens emulator is good for debugging spatial mapping as by default the emulator places itself into a “default room” and it can switch to a number of other rooms provided with the SDK and also to custom rooms that have been recorded from a HoloLens.

So, debugging on the emulator I can see that in the first instances here I see 22 loaded surfaces coming back from the SpatialSurfaceObserver;


and you can see the ID for my first surface and the UpdateTime that it’s associated with.

I also notice that very early on in the application I see the ObservedSurfacesChanged event fire and my code in SurfaceChangeWatcher simply calls back into the LoadSurfaces method shown in the screenshot above which then attempts to figure out which surfaces have been added/removed or updated since they were last queried.

So, getting hold of the surfaces within a volume and responding to their changes as they evolve doesn’t seem too onerous.

But, how to get the actual polygonal mesh data itself?

Getting Mesh Data

Once you have hold of a SpatialSurfaceInfo, you can attempt to get hold of the SpatialSurfaceMesh which it represents via the TryComputeLatestMeshAsync method.

This method wants a “triangle density” in terms of how many triangles it should attempt to bring back per cubic metre. If you’ve used the Unity prefab then you’ll have seen this parameter before and in my code here I chose a value of 100 and stuck with it.

The method is also asynchronous and so you can’t just demand the mesh in realtime but it’s a fairly simple call and here’s a screenshot of me back in the debugger having made that call to get some data;


That screenshot shows that I’ve got a SpatialSurfaceMesh and it contains 205 vertices in the R16G16B16A16IntNormalized format and that there are 831 triangle vertices in an R16Uint format and it also gives me the Id and the UpdateTime of the SpatialSurfaceInfo.

It’s also worth noting the VertexPositionScale which needs to be applied to the vertices to reconstruct them.

Rendering Mesh Data

Now, at this point I felt that I had learned a few things about how to get hold of spatial mapping meshes but I thought that it wasn’t really “enough” if I didn’t make at least some attempt to render the meshes produced.

I thought about a few options around how I might do that given that I’m running code inside of a 2D XAML application.

I wondered whether I might somehow flatten the mesh and draw it with a XAML Canvas but that seemed unlikely and I suspected that the best road to go down would be to keep the data in the format that it was already being provided in and try and hand it over to DirectX for rendering.

That led me to wonder whether something from Win2D might be able to draw it for me but Win2D stays true to its name and doesn’t (as far as I know) get into the business of wrapping up Direct3D APIs.

So…I figured that I’d need to bite the bullet and see if I could bring this into my 2D app via the XAML SwapChainPanel integration element with some rendering provided by SharpDX.

It’s worth saying that I’ve hardly ever used SwapChainPanel and I’ve never used SharpDX before so I figured that putting them together with this mesh data might be “fun” Winking smile

A UWP SharpDX SwapChainPanel Sample

In order to try and achieve that, I went on a bit of a search to try and see if I could find a basic sample which illustrated how to integrate SharpDX code inside of a XAML application rendering to a SwapChainPanel.

It took me a little while to find that sample as quite a few of the SharpDX samples seem to be out of date these days and I asked around on Twitter before finding this great sample which uses SharpDX and SwapChainPanel to render a triangle inside of a UWP XAML app;

That let me drop a few SharpDX packages into my project;


and the sample was really useful in that it enabled me to drop a SwapChainPanel into my XAML UI app and, using code that I lifted and reworked out of the sample, I could get that same triangle to render inside of my 2D XAML application.

That gave me a little hope that I might be able to get the mesh data rendered inside of my application too.

Building a SharpDX Renderer (or trying to!)

I wrote a class SwapChainPanelRenderer (source) which essentially takes the SwapChainPanel and my SurfaceChangeWatcher class and it puts them together in order to retrieve/monitor spatial meshes as they are produced by the SpatialSurfaceObserver.

The essence of that class is that it goes through a few steps;

  1. It Initialises D3D via SharpDX largely following the pattern from the sample I found.
  2. It creates a very simple vertex shader and pixel shader much like the sample does although I ended up tweaking them a little.
  3. Whenever a new SpatialSurfaceInfo is provided by the SurfaceChangeWatcher the renderer attempts asks the system to compute the mesh for it and creates a number of data structures from that mesh;
    1. A vertex buffer to match the format provided by the mesh
    2. An index buffer to match the format provided by the mesh
    3. A constant buffer with details of how to transform the vertices provided by the mesh
  4. Whenever the renderer is asked to render, it loads up the right vertex/index/constant buffers for each of the meshes that it knows about and asks the system to render them passing through a few transformation pieces to the vertex shader.

It’s perhaps worth noting a couple of things around how that code works – the first would be;

  • In order to get hold of the actual vertex data, this code relies on using unsafe C# code and IBufferByteAccess in order to be able to grab the real data buffers rather than copying it.

The second point that might be worth mentioning is that I spent quite a bit of time trying to see if I could get the mesh rendering right.

  • I’m not 100% there at the time of writing but what I have managed to get working has been done by consulting back with the official C++ sample which has a more complex pipeline but I specifically consulted it around how to make use of the SpatialSurfaceMesh.VertexPositionScale property and I tried to make my code line up with the sample code around that in as much as possible.

I must admit that I spent a bit of time staring at my code and trying to compare to the sample code as a way of trying to figure out if I could improve the way mine was seeming to render and I think I can easily spend more time on it to make it work better.

The last point I’d make is that there’s nothing in the code at the time of writing which attempts to align the HoloLens position, orientation and view with what’s being shown inside of the 2D app. What that means is;

  • The 2D app starts at a position (0,0.5,0) so half a metre above where the HoloLens is in the world.
  • The 2D app doesn’t know the orientation of the user so could be pointing in the wrong direction with respect to the mesh.

This can make the app a little “disorientating” unless you are familiar with what it’s doing Smile

Trying it Out

At the time of writing, I’ve mostly been trying this code out on the emulator but I have also experimented with it on HoloLens.

Here’s a screenshot of the official sample 3D app with its fancier shader running on the emulator where I’m using the “living room” room;


and here’s my 2D XAML app running in a window but, hopefully, rendering a similar thing albeit in wireframe;


and, seemingly, there’s something of a mirroring going on in there as well which I still need to dig into!

Wrapping Up & The Source

As I said at the start of the post, this one was very much just “for fun” but I thought I’d write it down so that I can remember it and maybe some pieces of it might be useful to someone else in the future.

If you want the source, it’s all over here on github so feel free to take it, play with it and feel very free to improve it Smile.

Windows 10, 1607, UWP and Experimenting with the Kinect for Windows V2 Update

I was really pleased to see this blog post;

Kinect demo code and new driver for UWP now available

announcing a new driver which provides more access to the functionality of the Kinect for Windows V2 into Windows 10 including for the UWP developer.

I wrote a little about this topic in this earlier post around 10 months ago when some initial functionality became available for the UWP developer;

Kinect V2, Windows Hello and Perception APIs

and so it’s great to see that more functionality has become available and, specifically, that skeletal data is being surfaced.

I plugged my Kinect for Windows V2 into my Surface Pro 3 and had a look at the driver being used for Kinect.


and I attempted to do an update but didn’t seem to see one but it’s possible that the version of the driver which I have;


is the latest driver as it seems to be a week or two old. At the time of writing, I haven’t confirmed this driver version but I went on to download the C++ sample from GitHub;

Camera Stream Correlation Sample

and ran it up on my Surface Pro 3 where it initially displayed the output of the rear webcam;


and so I pressed the ‘Next Source’ button and it attempted to work with the RealSense camera on my machine;


and so I pressed the ‘Next Source’ button and things seemed to hang. I’m unsure of the status of my RealSense drivers on this machine and so I disabled the RealSense virtual camera driver;


and then re-ran the sample and, sure enough, I could use the ‘Next Source’ button to move to the Kinect for Windows V2 sensor and then I used the ‘Toggle Depth Fading’ button to turn that option off and the ‘Toggle Skeletal Overlay’ button to switch that option on and, sure enough, I’ve got a (flat) skeletal overlay on the colour frames and it’s delivering very smooth performance here;


and so that’s great to see working. Given that the sample seemed to be C++ code, I wondered what this might look like for a C# developer working with the UWP and so I set about seeing if I could reproduce some of the core of what the sample is doing here.

Getting Skeletal Data Into a C# UWP App

Rather than attempting to ‘port’ the C++ sample, I started by lifting pieces of the code that I’d written for that earlier blog post into a new project.

I made a blank app targeting SDK 14393, made sure that it had access to webcam and microphone and then added in win2d.uwp as a NuGet package and added a little UI;


    <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
            Text="No Cameras" />

From there, I wanted to see if I could get a basic render of the colour frame from the camera along with an overlay of some skeletal points.

I’d spotted that the official samples include a project which builds out a WinRT component that is then used to interpret the custom data that comes from the Kinect via a MediaFrameReference and so I included a reference to this project into my solution so that I could use it in my C# code. That project is here and looks to stand independent of the surrounding sample. I made my project reference as below;


and then set about trying to see if I could write some code that got colour data and skeletal data onto the screen.

I wrote a few, small, supporting classes and named them all with an mt* prefix to try and make it more obvious which code here is mine rather than in the framework or the sample. This simple class delivers a SoftwareBitmap containing the contents of the colour frame to be fired as an event;

namespace KinectTestApp
  using System;
  using Windows.Graphics.Imaging;

  class mtSoftwareBitmapEventArgs : EventArgs
    public SoftwareBitmap Bitmap { get; set; }

whereas this class delivers the data that I’ve decided I need in order to draw a subset of the skeletal data onto the screen;

namespace KinectTestApp
  using System;

  class mtPoseTrackingFrameEventArgs : EventArgs
    public mtPoseTrackingDetails[] PoseEntries { get; set; }

and it’s a simple array which will be populated with one of these types below for each user being tracked by the sensor;

namespace KinectTestApp
  using System;
  using System.Linq;
  using System.Numerics;
  using Windows.Foundation;
  using Windows.Media.Devices.Core;
  using WindowsPreview.Media.Capture.Frames;

  class mtPoseTrackingDetails
    public Guid EntityId { get; set; }
    public Point[] Points { get; set; }

    public static mtPoseTrackingDetails FromPoseTrackingEntity(
      PoseTrackingEntity poseTrackingEntity,
      CameraIntrinsics colorIntrinsics,
      Matrix4x4 depthColorTransform)
      mtPoseTrackingDetails details = null;

      var poses = new TrackedPose[poseTrackingEntity.PosesCount];

      var points = new Point[poses.Length];

        poses.Select(p => Multiply(depthColorTransform, p.Position)).ToArray(),

      details = new mtPoseTrackingDetails()
        EntityId = poseTrackingEntity.EntityId,
        Points = points
      return (details);
    static Vector3 Multiply(Matrix4x4 matrix, Vector3 position)
      return (new Vector3(
        position.X * matrix.M11 + position.Y * matrix.M21 + position.Z * matrix.M31 + matrix.M41,
        position.X * matrix.M12 + position.Y * matrix.M22 + position.Z * matrix.M32 + matrix.M42,
        position.X * matrix.M13 + position.Y * matrix.M23 + position.Z * matrix.M33 + matrix.M43));

which would be a simple class containing a GUID to identify the tracked person and an array of Points representing their tracked joints except that I wanted those 2D Points to be in the colour space which means having to map them from the depth space that the sensor presents them in and so the FromPoseTrackingEntity() method takes a PoseTrackingEntity which is one of the types from the referenced C++ project and;

  1. Extracts the ‘poses’ (i.e. joints in my terminology)
  2. Uses the CameraIntrinsics from the colour camera to project them onto its frame having first transformed them using a matrix which maps from depth space to colour space.

Step 2 is code that I largely duplicated from the original C++ sample after trying a few other routes which didn’t end well for me Smile

I then wrote this class which wraps up a few areas;

namespace KinectTestApp
  using System;
  using System.Linq;
  using System.Threading.Tasks;
  using Windows.Media.Capture;
  using Windows.Media.Capture.Frames;

  class mtMediaSourceReader
    public mtMediaSourceReader(
      MediaCapture capture, 
      MediaFrameSourceKind mediaSourceKind,
      Action<MediaFrameReader> onFrameArrived,
      Func<MediaFrameSource, bool> additionalSourceCriteria = null)
      this.mediaCapture = capture;
      this.mediaSourceKind = mediaSourceKind;
      this.additionalSourceCriteria = additionalSourceCriteria;
      this.onFrameArrived = onFrameArrived;
    public bool InitialiseWithMediaCapture()
      this.mediaSource = this.mediaCapture.FrameSources.FirstOrDefault(
        fs =>
          (fs.Value.Info.SourceKind == this.mediaSourceKind) &&
          ((this.additionalSourceCriteria != null) ? 
            this.additionalSourceCriteria(fs.Value) : true)).Value;   

      return (this.mediaSource != null);
    public async Task OpenReaderAsync()
      this.frameReader =
        await this.mediaCapture.CreateFrameReaderAsync(this.mediaSource);

      this.frameReader.FrameArrived +=
        (s, e) =>

      await this.frameReader.StartAsync();
    Func<MediaFrameSource, bool> additionalSourceCriteria;
    Action<MediaFrameReader> onFrameArrived;
    MediaFrameReader frameReader;
    MediaFrameSource mediaSource;
    MediaCapture mediaCapture;
    MediaFrameSourceKind mediaSourceKind;

This type takes a MediaCapture and a MediaSourceKind and can then report via the Initialise() method whether that media source kind is available on that media capture. It can also apply some additional criteria if they are provided in the constructor. This class can also create a frame reader and redirect its FrameArrived events into the method provided to the constructor. There should be some way to stop this class as well but I haven’t written that yet.

With those classes in place, I added the following mtKinectColorPoseFrameHelper;

namespace KinectTestApp
  using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Numerics;
  using System.Threading.Tasks;
  using Windows.Media.Capture;
  using Windows.Media.Capture.Frames;
  using Windows.Media.Devices.Core;
  using Windows.Perception.Spatial;
  using WindowsPreview.Media.Capture.Frames;

  class mtKinectColorPoseFrameHelper
    public event EventHandler<mtSoftwareBitmapEventArgs> ColorFrameArrived;
    public event EventHandler<mtPoseTrackingFrameEventArgs> PoseFrameArrived;

    public mtKinectColorPoseFrameHelper()
      this.softwareBitmapEventArgs = new mtSoftwareBitmapEventArgs();
    internal async Task<bool> InitialiseAsync()
      bool necessarySourcesAvailable = false;

      // Find all possible source groups.
      var sourceGroups = await MediaFrameSourceGroup.FindAllAsync();

      // We try to find the Kinect by asking for a group that can deliver
      // color, depth, custom and infrared. 
      var allGroups = await GetGroupsSupportingSourceKindsAsync(

      // We assume the first group here is what we want which is not
      // necessarily going to be right on all systems so would need
      // more care.
      var firstSourceGroup = allGroups.FirstOrDefault();

      // Got one that supports all those types?
      if (firstSourceGroup != null)
        this.mediaCapture = new MediaCapture();

        var captureSettings = new MediaCaptureInitializationSettings()
          SourceGroup = firstSourceGroup,
          SharingMode = MediaCaptureSharingMode.SharedReadOnly,
          StreamingCaptureMode = StreamingCaptureMode.Video,
          MemoryPreference = MediaCaptureMemoryPreference.Cpu
        await this.mediaCapture.InitializeAsync(captureSettings);

        this.mediaSourceReaders = new mtMediaSourceReader[]
          new mtMediaSourceReader(this.mediaCapture, MediaFrameSourceKind.Color, this.OnFrameArrived),
          new mtMediaSourceReader(this.mediaCapture, MediaFrameSourceKind.Depth, this.OnFrameArrived),
          new mtMediaSourceReader(this.mediaCapture, MediaFrameSourceKind.Custom, this.OnFrameArrived,

        necessarySourcesAvailable = 
          this.mediaSourceReaders.All(reader => reader.Initialise());

        if (necessarySourcesAvailable)
          foreach (var reader in this.mediaSourceReaders)
            await reader.OpenReaderAsync();
      return (necessarySourcesAvailable);
    void OnFrameArrived(MediaFrameReader sender)
      var frame = sender.TryAcquireLatestFrame();

      if (frame != null)
        switch (frame.SourceKind)
          case MediaFrameSourceKind.Custom:
          case MediaFrameSourceKind.Color:
          case MediaFrameSourceKind.Infrared:
          case MediaFrameSourceKind.Depth:
    void ProcessDepthFrame(MediaFrameReference frame)
      if (this.colorCoordinateSystem != null)
        this.depthColorTransform = frame.CoordinateSystem.TryGetTransformTo(
    void ProcessColorFrame(MediaFrameReference frame)
      if (this.colorCoordinateSystem == null)
        this.colorCoordinateSystem = frame.CoordinateSystem;
        this.colorIntrinsics = frame.VideoMediaFrame.CameraIntrinsics;
      this.softwareBitmapEventArgs.Bitmap = frame.VideoMediaFrame.SoftwareBitmap;
      this.ColorFrameArrived?.Invoke(this, this.softwareBitmapEventArgs);
    void ProcessCustomFrame(MediaFrameReference frame)
      if ((this.PoseFrameArrived != null) &&
        (this.colorCoordinateSystem != null))
        var trackingFrame = PoseTrackingFrame.Create(frame);
        var eventArgs = new mtPoseTrackingFrameEventArgs();

        if (trackingFrame.Status == PoseTrackingFrameCreationStatus.Success)
          // Which of the entities here are actually tracked?
          var trackedEntities =
            trackingFrame.Frame.Entities.Where(e => e.IsTracked).ToArray();

          var trackedCount = trackedEntities.Count();

          if (trackedCount > 0)
            eventArgs.PoseEntries =
              .Select(entity =>
                mtPoseTrackingDetails.FromPoseTrackingEntity(entity, this.colorIntrinsics, this.depthColorTransform.Value))
          this.PoseFrameArrived(this, eventArgs);
    async static Task<IEnumerable<MediaFrameSourceGroup>> GetGroupsSupportingSourceKindsAsync(
      params MediaFrameSourceKind[] kinds)
      var sourceGroups = await MediaFrameSourceGroup.FindAllAsync();

      var groups =
          group => kinds.All(
            kind => group.SourceInfos.Any(sourceInfo => sourceInfo.SourceKind == kind)));

      return (groups);
    static bool DoesCustomSourceSupportPerceptionFormat(MediaFrameSource source)
      return (
        (source.Info.SourceKind == MediaFrameSourceKind.Custom) &&
        (source.CurrentFormat.MajorType == PerceptionFormat) &&
        (Guid.Parse(source.CurrentFormat.Subtype) == PoseTrackingFrame.PoseTrackingSubtype));
    SpatialCoordinateSystem colorCoordinateSystem;
    mtSoftwareBitmapEventArgs softwareBitmapEventArgs;
    mtMediaSourceReader[] mediaSourceReaders;
    MediaCapture mediaCapture;
    CameraIntrinsics colorIntrinsics;
    const string PerceptionFormat = "Perception";
    private Matrix4x4? depthColorTransform;

This is essentially doing;

  1. InitialiseAsync
    1. Using the MediaFrameSourceGroup type to try and find a source group that looks like it is Kinect by searching for Infrared+Color+Depth+Custom source kinds. This isn’t a complete test and it might be better to make it more complete. Also, there’s an assumption that the first group found is the best which isn’t likely to always hold true.
    2. Initialising a MediaCapture for the group found in step 1 above.
    3. Initialising three of my mtMediaSourceReader types for the Color/Depth/Custom source kinds and adding some extra criteria for the Custom source type to try and make sure that it supports the ‘Perception’ media format – this code is essentially lifted from the original sample.
    4. Opening frame readers on those three items and handling the events as frame arrives.
  2. OnFrameArrived simply passes the frame on to sub-functions based on type and this could have been done by deriving specific mtMediaSourceReaders.
  3. ProcessDepthFrame tries to get a transformation from depth space to colour space for later use.
  4. ProcessColorFrame fires the ColorFrameArrived event with the SoftwareBitmap that has been received.
  5. ProcessCustomFrame handles the custom frame by;
    1. Using the PoseTrackingFrame.Create() method from the referenced C++ project to interpret the raw data that comes from the custom sensor.
    2. Determining how many bodies are being tracked by the data.
    3. Converts the data types from the referenced C++ project to my own data types which include less of the data and which try to map the positions of joints given using 3D depth points to their respective 2D colour space points.

Lastly, there’s some code-behind which tries to glue this into the UI;

namespace KinectTestApp
  using Microsoft.Graphics.Canvas;
  using Microsoft.Graphics.Canvas.UI.Xaml;
  using System.Numerics;
  using System.Threading;
  using Windows.Foundation;
  using Windows.Graphics.Imaging;
  using Windows.UI;
  using Windows.UI.Core;
  using Windows.UI.Xaml;
  using Windows.UI.Xaml.Controls;

  public sealed partial class MainPage : Page
    public MainPage()
      this.Loaded += this.OnLoaded;
    void OnCanvasControlSizeChanged(object sender, SizeChangedEventArgs e)
      this.canvasSize = new Rect(0, 0, e.NewSize.Width, e.NewSize.Height);
    async void OnLoaded(object sender, RoutedEventArgs e)
      this.helper = new mtKinectColorPoseFrameHelper();

      this.helper.ColorFrameArrived += OnColorFrameArrived;
      this.helper.PoseFrameArrived += OnPoseFrameArrived;

      var suppported = await this.helper.InitialiseAsync();

      if (suppported)
        this.canvasControl.Visibility = Visibility.Visible;
    void OnColorFrameArrived(object sender, mtSoftwareBitmapEventArgs e)
      // Note that when this function returns to the caller, we have
      // finished with the incoming software bitmap.
      if (this.bitmapSize == null)
        this.bitmapSize = new Rect(0, 0, e.Bitmap.PixelWidth, e.Bitmap.PixelHeight);

      if (Interlocked.CompareExchange(ref this.isBetweenRenderingPass, 1, 0) == 0)

        // Sadly, the format that comes in here, isn't supported by Win2D when
        // it comes to drawing so we have to convert. The upside is that 
        // we know we can keep this bitmap around until we are done with it.
        this.lastConvertedColorBitmap = SoftwareBitmap.Convert(

        // Cause the canvas control to redraw itself.
    void InvalidateCanvasControl()
      // Fire and forget.
      this.Dispatcher.RunAsync(CoreDispatcherPriority.High, this.canvasControl.Invalidate);
    void OnPoseFrameArrived(object sender, mtPoseTrackingFrameEventArgs e)
      // NB: we do not invalidate the control here but, instead, just keep
      // this frame around (maybe) until the colour frame redraws which will 
      // (depending on race conditions) pick up this frame and draw it
      // too.
      this.lastPoseEventArgs = e;
    void OnDraw(CanvasControl sender, CanvasDrawEventArgs args)
      // Capture this here (in a race) in case it gets over-written
      // while this function is still running.
      var poseEventArgs = this.lastPoseEventArgs;


      // Do we have a colour frame to draw?
      if (this.lastConvertedColorBitmap != null)
        using (var canvasBitmap = CanvasBitmap.CreateFromSoftwareBitmap(
          // Draw the colour frame

          // Have we got a skeletal frame hanging around?
          if (poseEventArgs?.PoseEntries?.Length > 0)
            foreach (var entry in poseEventArgs.PoseEntries)
              foreach (var pose in entry.Points)
                var centrePoint = ScalePosePointToDrawCanvasVector2(pose);

                  centrePoint, circleRadius, Colors.Red);
      Interlocked.Exchange(ref this.isBetweenRenderingPass, 0);
    Vector2 ScalePosePointToDrawCanvasVector2(Point posePoint)
      return (new Vector2(
        (float)((posePoint.X / this.bitmapSize.Value.Width) * this.canvasSize.Width),
        (float)((posePoint.Y / this.bitmapSize.Value.Height) * this.canvasSize.Height)));
    Rect? bitmapSize;
    Rect canvasSize;
    int isBetweenRenderingPass;
    SoftwareBitmap lastConvertedColorBitmap;
    mtPoseTrackingFrameEventArgs lastPoseEventArgs;
    mtKinectColorPoseFrameHelper helper;
    static readonly float circleRadius = 10.0f;

I don’t think there’s too much in there that would require explanation other than that I took a couple of arbitrary decisions;

  1. That I essentially process one colour frame at a time using a form of ‘lock’ to try and drop any colour frames that arrive while I am still in the process of drawing the last colour frame and that ‘drawing’ involves both the method OnColorFrameArrived and the async call to OnDraw it causes.
  2. That I don’t force a redraw when a ‘pose’ frame arrives. Instead, the data is held until the next OnDraw call which comes from handling the colour frames.It’s certainly possible that the various race conditions involved there might cause that frame to be dropped and another to replace it in the meantime.

Even though there’s a lot of allocations going on in that code as it stands, here’s a screenshot of it running and the performance isn’t bad at all running it from my Surface Pro 3 and I’m particularly pleased with the red nose that I end up with here Smile


The code is quite rough and ready as I was learning as I went along and some next steps might be to;

  1. Draw joints that are inferred in a different colour to those that are properly tracked.
  2. Draw the skeleton rather than just the joints.
  3. Do quite a lot of optimisations as the code here allocates a lot.
  4. Do more tracking around entities arriving/leaving based on their IDs and handle multiple people with different colours.
  5. Refactor to specialise the mtMediaSourceReader class to have separate types for Color/Depth/Custom and thereby tidy up the code which uses this type.

but, for now, I was just trying to get some basics working.

Here’s the code on GitHub if you want to try things out and note that you’d need that additional sample code from the official samples to make it work.

Windows 10 1607, UWP, Composition APIs–Walked Through Demo Code

I’ve written a few posts about the Windows 10 composition APIs for beautiful, fluid, animated UX gathered under this URL;

Composition Posts

and today I was putting together some demo code for other purposes and I thought I’d screen-capture what I had as a walk through of some of the capabilities of those composition APIs starting from a blank slate and walking through it;

That’s just one of my own, unofficial walk-throughs. For the official bits, visit the team site at;

Enjoy Smile