---
title: "Check camera positions"
canonical: "https://help.vicon.com/space/Evoke15/10325920/Check%20camera%20positions"
format: markdown
---
Evoke enables you to check whether any cameras have moved by comparing the current camera positions with a snapshot (baseline) of camera LEDs from the previous Evoke session. It also provides information on when a re-calibration is required.
When you first start using your Origin system, it is advisable to run a calibration assessment daily, before use. When you have become familiar with how much the rig shifts or cameras get knocked, you may be able to reduce the frequency of this check.
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## Generate baseline
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To generate information on the cameras' current positions:
- On the **Calibration Assessment** tab, click **Generate Baseline**.Blue marks are displayed next to most cameras. Each mark represents the LEDs of the other cameras that can be seen by the camera.
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## Assess current calibration
After you have generated a baseline from which the camera positions can be assessed, you check for camera movement. To do this:
- On the **Calibration Assessment** tab, click **Assess Calibration**.
On the **Calibration Assessment** tab,most or all of the blue marks turn green.
Green marks indicate that the camera position is unchanged since the last calibration.
Red marks indicate that something has changed in the calibration, either due to a bump or knock, or because of environmental drift.
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Depending on whether you have Enable Auto Bump Healing selected (the default), you may need to take action to correct any changes.
- [Enable automatic recovery of moved cameras](#EnableAutoRecovery)
- [Manually recover moved cameras](#ManuallyRecoverCameras)
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## Enable automatic recovery of moved cameras
When you run **Assess Calibration**, Evoke may indicate that a camera has been moved. If a camera has been bumped enough to move its position, the move is detected, so the LEDs flash red on the camera, and the **System** pane and **Cameras** view display a bump icon to the right of the camera name.
**To enable the recovery of a moved camera:**
1. On the **Processing** tab, go to the **Camera Healing** section and make sure **Enable Auto Bump Healing ** is selected (its default setting).
2. In the volume, have someone wave two of the Pulsars used to set the floor plane in front of the camera until its status light turns blue (or magenta if selected).
3. To generate a new baseline, on the **Calibration Assessment** tab click **Generate Baseline**. This creates a baseline that contains the updated information about the camera positions.
For more information:
- For Vicon systems that use cameras with built-in strobes (such as Vero or Vantage cameras), see [Automatic recovery for systems with strobed cameras](#autoBumpHealPassive).
- If Auto Bump Healing doesn't seem to be recognizing or recovering cameras that have moved, see [Understand automatic recovery of moved cameras](#UnderstandAutoHeal).
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Automatic recovery for systems with strobed cameras
Auto Bump Healing is turned on by default.
> ❌ **Caution**
> ❌ If the environment has many infra-red sources or reflective surfaces that interfere with data that is being processed by the camera, Auto Bump Healing can adversely affect the calibration rather than rectifying it. When **Generate Online Masks **is selected, the static centroids generated from these sources are automatically filtered out when the camera health signals that are used to trigger auto bump healing are generated.
The option for generating online masks is disabled by default. To enable this option, which is recommended for use with Vicon systems that include cameras with built-in strobes (such as Vero or Vantage cameras):
1. In the **Processing** panel, ensure the **Advanced** properties are displayed.
2. In the **Camera Healing** section, select **Generate Online Masks**.
In some situations, you may need to deactivate Auto Bump Healing, for example, for systems where there is no overhead for the additional processing required, and in some cases where large numbers of centroids are generated from non-object sources (eg, reflections from participants' clothing). In this latter case, some other mitigation is often available (eg, by reducing the strobe intensity of the cameras), but in extreme cases it may be better to deactivate Auto Bump Healing.
To turn off Auto Bump Healing, on the **Processing** tab, go to the **Camera Healing** section and clear **Enable Auto Bump Healing**.
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Understand automatic recovery of moved cameras
When **Enable Auto Bump Healing ** is selected, the system detects cameras that have stopped contributing centroids to the tracked objects in the volume if:
- The system health connection score for the camera is below 25% (to check this, at the top of the **Cameras** view, hover the mouse pointer over the Connection score icon > Macro (inline-media-image)
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- Enough centroids are visible to this camera.
> ⚠️ **Important**
> ⚠️ For Auto Bump Healing to work, at least 50% of the enabled objects must currently be tracked by the cameras.
> ⚠️ For this reason, disable any objects that can't be tracked (ie, any Pulsars that are charging, powered off or out of the volume).
If these criteria are met, the system attempts to bump-heal (recover the position of) the camera. It collects data for a short time and if there is sufficient coverage in the cameras view and the system can find a solution, it applies a new calibration for this camera. This causes the system calibration file to be re-saved to the following default location:
*C:\ProgramData\Vicon\Calibrations\LatestCalibration.xcp*
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For successful automatic recovery of moved cameras, ensure that your system meets the following criteria:
- The cameras’ internal parameters (focal length, radial distortion, etc) do not change.
- The cameras have achieved a stable operating temperature before calibration and before starting an experience.
- Objects are being tracked by a majority cameras. The easiest way to check this is to select all cameras (or no cameras), look in the **Cameras** view and in **View Filters** ensure **Centroids** is selected. Check that the centroids are green and that no calibration warning icons are displayed.
- The bumped camera(s) can see objects and they are generating 2D tracks.
- No unmasked camera strobes or reflective objects are present in the system. These may cause the system health of the camera to remain low and to trigger further recalibration.
If you need further information about which camera has moved, what may be causing an issue and whether it has been successfully recovered, check the Log (if it isn't displayed, on the **View** menu, select **Log**). The errors, warnings and messages will look similar to this:
In the above examples, the camera's Device ID is highlighted.
To find a camera's Device ID, on the **System** tab, select the camera, click **Show Advanced** in the **General** section, scroll to **Device ID**.
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## Manually recover moved cameras
When you run **Assess Calibration**, Evoke may indicate that a camera has been moved. On the moved camera, the LEDs to flash red and on the **System** tab and **Cameras** view, the bump icon is displayed to the right of the camera name.
If **Enable Auto Bump Healing ** (see above) is not selected, you can recover a moved camera by using Evoke's **Recover Camera Position** option.
**To recover a moved camera:**
1. In the **Tools** pane, on the **Camera Calibration** tab, click **Start ****Recover Camera Position** and in the volume, wave two of the Pulsars in front of the affected camera.
In the **3D Scene** and **Cameras** view, orange trails are displayed as the system determines the offset between the camera and the rest of the calibration.
2. When enough of the view has been covered (indicated by orange trails that thickly cover the affected camera view), click **Recover Camera Position**.
3. In the **Cameras** view, zoom in and check that the centroids are now green, and the red icon to the right of the camera names have gone.
4. To generate a new baseline, on the **Calibration Assessment** tab click **Generate Baseline**. This creates a baseline that contains the updated information about the camera positions.
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Compensate for camera calibration drift
When small changes occur in the pose or internal parameters of the camera (eg, through temperature changes that cause the thermal expansion of the rig), this can cause centroids to fail to be labeled as part of a tracked object.
The Auto Bias Handling feature attempts to compute the camera calibration biases and increase the slack used when deciding whether a centroid should correspond to a model point in order to compensate.
**To turn Auto Bias Handling on or off:**
1. In the **Processing** panel, ensure the Advanced options are displayed.
2. Go to the **Camera Healing** section and select or clear **Enable Bias Handling**. This option is selected by default.
The bias correction does consume additional CPU resources but is unlikely to affect experience latency for standard tracking.
This parameter can be thought of as an automated version of the Environmental Drift Tolerance parameter for reconstructions, but dedicated to object tracking. Note that if objects are struggling to boot, you may also need to increase the Environmental Drift Tolerance.