Calibrate cameras

When you first connect up your Vicon system and start Vicon Shogun Live, notice that in both the System panel and in the Cameras view, icons give you feedback on the current status of the cameras. The cyan icons indicate that although the cameras are connected, they are not yet calibrated.

With Shogun Live 1.6 and later, to avoid having to recalibrate the whole system when you make changes such as adding or moving some of the cameras, you can Calibrate or recalibrate selected cameras.

See also the Vicon video: 4 - Shogun Live - System Calibration.

Mask cameras

You mask cameras, including supported video cameras, during camera calibration to eliminate any unwanted reflections in the capture volume, so that they are not mistaken for markers by the cameras. Before you start masking, you can see these reflections represented by light pixels in the Camera views. During masking, blue pixels are drawn in the Cameras views, enabling you to see how much of the view is masked.

To mask reflections:

1. Ensure you have removed any objects likely to cause reflections, such as the calibration device or markers, from the capture volume.
2. To display the required panels, in the Load Saved View list, click System Setup.

   

3. In the System panel, SHIFT+click or drag to ensure all the cameras are selected, including any video cameras in your Vicon system.
4. On the Camera Calibration tab, click Start Masking (All).

   

   The button displays Stop Masking and at the top of the workspace, Auto Mask Active is displayed.

   

   In the Cameras views, any video cameras are displayed as black, blank screens.
   Shogun Live starts recording the data visible to each of the connected cameras. Any camera masks created are displayed as blue cells in the Cameras views for affected cameras. If no data is visible to a particular camera, Shogun Live does not create any masks for it. Both optical and video cameras are masked.
5. After about 5–10 seconds, click Stop Masking.
6. In the Cameras view for each camera, ensure that any unwanted reflections are eliminated. (Each view should either be completely blank or should contain some blue pixels.)

When you've masked all the reflections, you can capture a wand wave.

If you need to add equipment or make other changes after you've finished masking, see Change masking.

Change masking

If you add equipment or markers into the volume after you’ve finished auto-masking, or if you have an issue with specific camera(s), you'll need to add to any masking that you've already completed. To do this, you can keep your original masking and use further auto-masking to add to it and/or manually paint out any additional reflections.

To add to existing auto-masking:

1. To display the required panels, in the Load Saved View list, click System Setup.
2. If you want to apply additional masking to only some cameras, make sure you've selected the relevant cameras.
3. On the Camera Calibration tab, ensure the Advanced options are displayed and clear the Clear Previous Masks check box. This prevents your original masking from being overwritten.
4. If you want to add the new masking to selected cameras only, in the Cameras To Mask list, ensure Selected Cameras Only is selected.
5. Click Start Masking.

   

   Auto Mask Active is displayed at the top of the Workspace.
6. When masking is complete, click Stop Masking.
   In the Cameras views, observe the additional masking, which is displayed as blue cells.

To manually add masking:

1. To display the required panels, in the Load Saved View list, click System Setup.
2. On the Camera Calibration tab, click Start Manual Mask Paint.
   Manual Mask Painting Active is displayed at the top of the Workspace.
3. Use the following shortcuts to select and mask:
   • To select an area: Alt+click and drag
   • To apply masking: Click on the pencil icon next to the pin button or use the shortcut Alt+E.

     

   • To erase masking: Select the masked area (see above) and click the eraser or use the shortcut Alt+R.

     

4. When you have finished manual masking, click Stop Manual Mask Paint.

When you've masked all the reflections, you can capture a wand wave.

Capture a wand wave

During camera calibration, after you have masked any reflections, you calibrate the cameras by waving a wand (the calibration device) throughout the volume to enable the cameras to capture movements over the whole area.

To capture a wand wave:

1. At the top of the Camera Calibration tab, in the Wand list, ensure the option for the type of wand that you are using is selected (this will normally be one of the Active Wand options).
2. To start collecting wand data, click Start Wave.
   The button displays Stop Wave and in the menu bar, the text Camera Calibration Active is displayed, next to a flashing red circle.

3. Have someone wave the wand throughout the capture volume, covering depth as well as height, while you watch the Cameras views for all cameras to ensure you get full coverage. Ensure that the markers (LEDs) on the wand remain visible to all the cameras as much as possible while the wand is moved throughout the volume.
   As an indication that sufficient wand wave data has been collected for a particular camera, the display in the each view changes from orange to blue.
   
   

4. In the table in the bottom half of the Camera Calibration tab, notice that the Wand Count column changes from red to green as sufficient data per camera is captured. This helps you concentrate on waving the wand for cameras that need more data.

   Tip: By default, camera calibration stops automatically when each camera has seen enough of the wand to ensure calibration. To adjust this or turn it off, at the top right of the Camera Calibration tab, click Show Advanced and then click the ellipsis (…) to the right of the Start Wave button.

5. In the Image Error column, in addition to displaying the values, Shogun Live grades the status of each camera between red (poor) and green (excellent), depending on how much the cameras see the wand.
   In the volume, the display on Vicon optical cameras changes to indicate their calibration status:
   • Vantage, Vero, Viper and ViperX cameras: The status lights turn magenta and blink during calibration, becoming green and then blue when fully calibrated. On the OLED display (Vantage cameras only), a pie chart indicates the fraction of the required wand data that has been received from the camera.
   • MX T-Series cameras: The status light on the front blink while you are performing the wand wave, and then go solid blue when enough data has been collected to calibrate the camera.

6. When enough data has been collected, Shogun Live starts processing the wand wave data. Depending on the number of cameras and the length of your wand wave capture, this may take a few minutes. The progress bar indicates the calibration progress, and table below indicates the calibration results.
   

   In the Log, you are warned if your wand wave has insufficient spread across cameras to give a good calibration. The warning displays both the camera User ID (the number you can provide for the camera in the camera's properties, and URN (the Device ID, found in the camera's Advanced properties).

   

7. When the wand wave is finished, an .xcp and an .x2d file is created in C:\ProgramData\Vicon\Calibrations. If your calibration included Vicon video cameras, two x2d files are created. The files are:

   • LatestCalibration.x2d, which contains the wand wave without any Vicon video cameras

   • LatestCalibration_withVideo.x2d, which contains the wand wave including Vicon video cameras.

Set the volume origin

Set the floor plane

The final stage in calibrating your Vicon cameras is to set the floor plane, using markers in the volume to automatically define it.

The position of the virtual floor that is derived during setting the origin is extrapolated from the position of the wand in relation to floor of the volume. As the wand is a small object compared with the size of the volume, any slight discrepancy from the wand being level has a large effect over the rest of the volume when you set the origin. To account for any discrepancy, you set a floor plane, which takes a much larger area into account, so that the virtual floor lines up correctly with the actual floor plane.

To set the floor plane:

1. Ensure you have completed the rest of the camera calibration procedure and set the origin (see Set the volume origin).
2. Turn off the calibration object or remove it from the volume.
3. Place a minimum of four 14 mm Vicon markers across the floor of your capture volume.
   (If you are not using 14 mm markers or have changed the default 7 mm floor plane setting, see Adjust the Set Floor Plane settings.)
4. On the Camera Calibration tab, click Start Set Floor Plane.
   The button displays Set Floor Plane.
5. After a few seconds, click Set Floor Plane.
6. In the 3D Scene, display the View Filters options and under the Volume options, ensure that Cameras is selected
   In the Perspective view, note that the cameras shift as a group slightly along one or more rotation axes to better reflect an average of the markers scattered across the floor, taking into account any offsets that you specified.
   In C:\ProgramData\Vicon\Calibrations, the LatestCalibration.xcp file is updated. This file is automatically used for every subsequent capture.

   Tip: To more accurately visualize the size of your volume in Shogun Live, you can change the size and shape of the floor grid. To do this, on the Camera Calibration tab, click the ellipsis (...) next to Set Floor Extents and change the values (in mm) to give the required result.

If your system includes supported video cameras, you can now check that your video calibration is accurate by viewing a video overlay.

To check a video overlay:

1. In the System panel, expand the Video Cameras section and click on one or more video cameras.
   The Cameras view displays the video data for the selected video camera(s).
2. In the Cameras view, click View Filters and in the 3D Data section, select the 3D option.
   In the view pane, a 3D overlay is displayed. Because this displays a flat overlay on a 3D Scene, the edges appear distorted.
3. To remove the distorted appearance, select Distort 3D.
   The 3D perspective is flattened to match the video.

   

4. Check that the video of the markers and the 3D perspective line up accurately.

   Tip: To check your calibration, from the View Filters options, select Camera Rays. If you select one or more cameras, this displays lines (rays) to everything the selected camera(s) can see. If you select one or more markers, this option displays lines from all cameras that can see the selected marker(s).

Your Vicon cameras are now calibrated and ready to capture data.

Adjust the Set Floor Plane settings

If you are not using 14 mm markers, to enable you to set the floor plane accurately, click Show Advanced, click the ellipsis next to Start Set Floor Plane, and change the Height offset value to an appropriate value. The Height offset is the amount (in mm) by which to adjust the floor plane (the default is 7 mm). Because Shogun finds the centers of the markers, set a Height offset that accounts for the size of the markers (for example, for 14 mm markers, the Height offset is 7 mm). If the markers include a base, take this into account in your calculations.

Auto number cameras

The Auto Number Cameras feature numbers the currently connected Vicon cameras in ascending order, according to their position in the capture volume. You may want to do this after you calibrate your Vicon system, so that your cameras are logically numbered before you begin capture.

Automatic numbering starts with the camera that is furthest from the volume origin. The cameras are then numbered in a clockwise direction around the volume. If your cameras are positioned at different levels, the cameras in the level that contains the most cameras are numbered first.

To automatically number Vicon cameras:

1. Ensure that the cameras are positioned as required, and that you have calibrated the cameras and set the volume origin.
2. To enable you to check the camera numbering for all cameras, in the System panel, ensure that you can see the list of Vicon cameras.
3. In the Camera Calibration panel, click Auto Number Cameras.
   The cameras are automatically numbered in ascending order, according to their position in the volume.
   In C:\ProgramData\Vicon\Calibrations, the LatestCalibration.xcp file is updated.
4. In the volume, check that the cameras are now numbered as required.