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Troubleshooting object detection

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This article assumes you already converted a 3D model into an Azure Object Anchors detection model and successfully loaded the model into an application.

Troubleshooting steps

  • Ensure that the model you're detecting is within the supported (1-10 meters) size for the best experience.
  • Ensure the room has enough textures by adding a few posters.
  • Remove current holograms to reset the map as described below.
  • Scan the object more completely.
  • Provide a tight bounding box as search area that includes all or most of the object.
  • Clear the spatial mapping cache and rescan the object.
  • Ensure the correct gravity direction and asset dimension were used during model conversion as described below.
  • Visually inspect the detection model as described below.
  • Adjust the model query values as described below.
  • Capture diagnostics as described below.

Remove holograms to reset the map

If you're seeing objects being detected with any of the follow issue, removing and resetting the map can fix the issue:

  • Inverted orientation
  • Incorrect pose
  • Tilted model

To remove holograms and reset the map, open the Settings app and go to System -> Holograms. Then, select Remove all holograms to start with a fresh map.

Clearing the holograms ensures objects can be properly detected in their current positions in case they were recently moved.

Rescan your environment by walking around in the environment wearing the HoloLens. Walk around any objects you intend to detect a few times from 1-2 meters.

Ensure the gravity direction and asset dimension unit are correct

When you submit a 3D model for conversion using the Object Anchors Conversion SDK (see here), you'll need to enter correct gravity direction (Gravity) and unit of measurement (AssetDimensionUnit) for your 3D model. If those values aren't correct, Object Anchors is unlikely to detect your object correctly.

The gravity direction is the down vector pointing to the earth. For CAD models, gravity direction is typically the opposite of an up direction. For example, in many cases +Z represents up, in which case -Z or Vector3(0.0, 0.0, -1.0) would represent the gravity direction. When determining gravity, you should also consider the orientation in which the model will be seen during runtime. If you're trying to detect a chair in the real world on a flat surface, gravity might be Vector3(0.0, 0.0, -1.0). However, if the chair is on a 45-degree slope, gravity might be Vector3(0.0, -Sqrt(2)/2, -Sqrt(2)/2).

The gravity direction can be determined with a 3D rendering tool, like MeshLab.

The unit of measurement represents the scale of the model. Supported units can be found using the Microsoft.Azure.ObjectAnchors.Conversion.AssetLengthUnit enumeration.

You can also follow the instructions here to visualize a detection model in Unity to visually inspect that gravity direction and scale look correct.

Visually inspect the detection model's mesh

Sometimes it can be helpful to visually inspect the detection model's mesh so that you can see any orientation, scale, or feature issues. Follow the instructions here to visualize a converted model in Unity.

Adjust object query values

  • Provide tight search areas to ideally cover the full object to improve detection speed and accuracy.
  • The default ObjectQuery.MinSurfaceCoverage value is often sufficient, but you can use a smaller value to get a quicker detection.
  • Use a small value for ObjectQuery.ExpectedMaxVerticalOrientationInDegrees if the object is expected to be up-right.
  • An app should always use a 1:1 object model for detection. The estimated scale should be close to 1 ideally within 1% error. An app could set ObjectQuery.MaxScaleChange to 0 or 0.1 to disable or enable scale estimation, and qualitatively evaluate the instance pose.
  • For more information, see How to detect a difficult object.

Capture diagnostics

The application can capture and save diagnostics archives using the ObjectDiagnosticsSession object.

The Unity sample app with MRTK writes diagnostics to the TempState folder. You can start a diagnostics session by opening the hand menu, selecting Start Tracing, reproducing a detection attempt, and then select Stop Tracing to save the diagnostics archive. You can then use Windows Device Portal to retrieve the diagnostics archive from the app's TempState folder.

The diagnostics archive can then be shared with us so that we can help debug the issue.

Next steps

In this troubleshooting guide, you learned how to troubleshoot detection of a physical object using Azure Object Anchors. Here are some related articles:

How to detect a difficult object

How to visualize an Object Anchors model