Use AR Visualization mode

Note that ARKit was developed by a third party so its data is independent of the data obtained from the Blue Trident sensors. This can cause: 

• Inconsistent behavior or stability, depending on the iOS device used
• Asynchronous data when compared with the Blue Trident data

To limit bandwidth issues (ie, dropped frames), we recommend using one of the other modes for collection, particularly if you want to ensure overall app stability.

Note that as data is streamed over Bluetooth^®, external factors can also cause dropped samples. If this is an issue, you can either interpolate between samples or use To Sensor mode instead, to avoid dropped samples altogether.

Summary of AR Visualization mode

To use AR Visualization mode:

1. Open the Capture.U app.
2. In the Visualize section tap AR Visualization.
3. Select one of these options:
   
   • Acceleration (x, y, z, or Resultant and Low g or High g)

     Note that Resultant is the peak resultant acceleration, which is calculated by

      

     With the High g accelerometer selected, the resultant acceleration can reach up to 346 G.

     With the the Low g accelerometer selected, the resultant acceleration can reach up to 26 G.

   • Rotation (x, y, or z)
     To enable Global Angles, select Rotation and ensure Global is selected.

      

     Global angles are streamed in real time on the graph. They are visualized as Euler angles (XYZ rotation order) and exported as Euler angles and quaternion components (Qx, Qy, Qz, Qr).

     Note that when Global Angles is selected, Low g Accelerometer, Gyroscope, and Magnetometer are also collected and the capture rate is reduced to 225 Hz (A, G) 70 Hz (M) for the Low g sensor.

   • Joints, which lets you select two joint angles that are derived from the Apple ARKit 3 (tap Joint 1, select the required joint, then tap Joint 2 to select it). 

      

4. At the top right of the screen, you can select whether the joint transforms are model transforms (relative to the root joint) or local transforms (relative to the parent). The default setting is Model.

    

5. At the bottom left of the screen, tap Select Sensors. 

    

   While you are selecting sensors, if you chose to collect Global Angles, one or more of the sensors may be displayed with a 'Require calibration' icon  or a 'Calibrated' icon  at its top right. For further explanation, see Step 7.

6. Select up to two sensors (for details, see Capture to sensor, Step 7), and then tap Set.

   
   You can edit the name of any sensor in this list by swiping left on the specific sensor and selecting Edit Name. For more information, see Manage sensor names.

7. At the bottom of the screen, tap Start.
   

   If you chose to collect Global Angles:

   1. If one or more of the selected sensors requires calibration, after you tap Start to start collection, on the next screen, a message at the the bottom of the screen prompts you to begin calibration when the trial starts. 
   2. Calibrate any sensors that are uncalibrated. For more information on calibration, see Calibrate IMUs.
   3. When you've finished moving the sensor, to verify your calibration, check that the graphs for all three axes are now at zero.
8. To play a sound when a specified level is reached, in the Benchmarks area, enter the required values in the benchmark fields.
   The values are indicated by a shaded area on the graph.

9. To record real-time video (recorded at 1920 x 1080), tap the Video icon  at the top right of the screen.

   The graph is overlaid on the video. To make the graph easier to see, the controls at the top of the screen enable you to change the thickness of the lines (slide right to increase line thickness), the opacity of the graph, and select a dark or light version.

    

   When a subject is visible, the AR figure automatically overlays its image.

    

10. To offset the skeleton from the tracked subject, use the Model Offset slider at the top left of the screen to apply the required offset.

     

11. To enable or disable 2D and 3D skeleton visualization, select the required 2D Skeleton and 3D Skeleton option(s) below the Video icon.

    You can select 2D, 3D, or both.

     

12. To see statistics for the collection in real time, tap the Statistics icon , towards the bottom right of the screen.

    The minimum and maximum values detected by the sensors are displayed, in addition to how many times the benchmark values have been reached.

     

13. When you have collected the required movement, tap Stop.
14. From the export icons, select the required export type (file or video):
    

    • To save a video to your device, tap the Video icon (top right) and then tap Save.

       

      Depending on the length of your video, this may take some time. Don't tap Save again, but wait until the video is saved.

      Tip: Find saved videos on the Photos tab in the Photos app .

      • If you choose Export to PDF, you can add a title in the PDF preview that is displayed.

        The preview shows the information that will be displayed in the exported PDF, with statistics information at the top of the page, a Focused view of the graph (showing the region of interest) and Full Range view (showing the whole range). This lets you check that the graph is as required before you export it. If it isn't, tap Cancel, change the Joints, Acceleration and/or Rotation to show a graph of the required view (X, Y, Z, or Resultant) and tap Export to PDF again.

        When you're happy with the preview, tap Export at the top to export the PDF.

         

      • If you choose Export to CSV, the data within the sensor file will depend on what is displayed during collection. This sensor data is always exported as X, Y and Z, but not Resultant.
        Joint data is always exported in separate files, according to their joint name. 
        The format for joint data is always in the following format: 2D joints (x and y, which are positions in screen space where the joint was tracked via image processing), 3D joint translations (Tx, Ty, Tz, relative to the root joint if model transforms are selected, or relative to the parent joint if local transforms are selected) and in quaternion format: Qx, Qy, Qz, Qr, with Qr being the real component representing the rotation.

        

        Tip

        • If you chose to display High g acceleration, High-G and joint data is exported.

        • If you chose to display Joints, Low-G accelerometer and gyroscope data is exported in a file according to its sensor name with joint data.

        • If you chose to display Global Angles, all data is exported in the sensor file with the following format: Low-G accelerometer, gyroscope, magnetometer, global angles quaternion, global angles helical, and global angles EulerXYZ.

        To export either a report (.pdf) or data (.csv), or to browse previously recorded videos, tap the File icon (top right).

         

      • If you choose Browse Video, previously collected videos are listed. Tap to select a video, then play a minimized preview by tapping the Play icon at the bottom, or tap Use at the top right to play in full-screen mode. 

Protect collected data

In Capture.U 1.4.1 or later, if you have collected data, AR Visualization prompts you to export your data before collecting a new trial or navigating back to the home page.

Select the required option:

• To continue with the current action, tap OK.
  This will result in you losing the current collected data.
• To terminate the current action, tap Cancel.
  This retains the current collected data.