View source for Multiple PS Eye Cameras Calibration

{{:Calibration Definition}}

=== Importance of high frame rate ===

You should record calibration video at the same resolution as your action video and at the same (or higher) frame rate. 

Calibration at a different resolution may lead to reduced accuracy because cameras usually have different minor distortions at different resolutions (caused by internal scaling algorithm).

Calibration at low frame rate may lead to reduced accuracy because of increased synchronization errors. 

=== Glowing Marker ===
{{:Glowing Marker}}

=== Step 1: Running [[iPi Recorder]] in Calibration Mode ===

Run [[iPi Recorder]] and choose one of the darkening modes in "darkening for calibration" list (for Sony PS Eye cameras)
[[File:Calibration-darkening.png|center|link=]] 

or set Exposure to reasonably small value (for DirectShow-compatible web cameras) 

[[File:Calibration-exposure.png|center|link=]]

This is important because it helps to reduce motion blur during calibration. 

Video will look dim in calibration mode.

{{Important|Do not turn off the light in the room during calibration! This will not help the software but will make it harder for you to see what is happening on recorded video when you view it later.}}

=== Step 2: Record Calibration Video ===

Start video recording.

Move the marker slowly through your entire capture volume (front-top-right-bottom-left-back-top-right-bottom-left).  Start from top and move the marker in a descending spiral motion.

{{Tip|The exact trajectory of the marker is not so important, just try to cover the whole capture volume, or at least its perimeter.}}

{{Tip|For successful calibration, several hundred frames are sufficient. Much more frames (like several thousands) will not produce more accurate results, but instead will increase the processing time and possible number of marker detection errors. So generally it is not recommended to record calibration videos of more than 1 minute length.}}

{{Tip|You should make the marker visible to as much cameras as possible at all times. Hold the marker in the straight arm away from your body. In a circle configuration, when approaching the boundary of the capture area, position the marker inside the area, and your body outside.}}

[[File:Calibration1.jpg|center|link=]]

[[File:Calibration2.jpg|center|link=]]

[[File:Calibration3.jpg|center|link=]]

Put the marker to the ground at each corner and at the center of capture volume. At least 4-5 ground points are needed for the correct detection of the groundplane.
<center>
{|
|[[File:Calibration_ground1.jpg|center|400px]]
|[[File:Calibration_ground2.jpg|center|400px]]
|}
</center>

=== Step 3: Stop Recording and Check Recorded Video ===

Check the video and make sure that:

* There is no significant motion blur (image of marker looks like a round spot rather than an ellipse or a luminescent line)
* Most of the time (80%-90% of all recording time) marker is visible in all cameras

=== Step 4: Take Note of Height of Your First Camera Over the Ground. ===
 
Take note of height of your first camera over the ground. You will need this parameter later. 

=== Step 5: Process Calibration Video in [[iPi Mocap Studio]] ===

{{Tip|You can postpone processing calibration video until after you finished recording other videos (e.g. your action videos). However, it is a good idea to process your calibration video as soon as it was recorded because it helps you ensure that you have good calibration. Use '''Regular''' calibration mode (1) if you want to be 100% sure that calibration sequence is fine. Also you can use '''Fast''' calibration mode to save time. But in this case you will need to re-process calibration video later to get maximum calibration quality. I certain cases '''Fast''' calibration mode can fail to calibrate even if calibration sequence is fine and can be calibrated successfully in '''Regular''' calibration mode.}}

To process calibration video please do the following: 
* Create new calibration project in [[iPi Mocap Studio]]:
** Press ''New'' button or select '''File > New Project''' menu item or use <tt>Ctrl+N</tt> (2) 
*:[[Image:Calibration_Start.png|center|800px]]
** Choose '''Calibration project''' type in '''New Project Wizard'''.
** Set the diagonal '''Field of View''' (FOV) for your cameras. 
*:{{Note|If you use Sony PS Eye or Logitech QuickCam 9000 cameras, leave the FOV value at the default 75 degrees.}}
<center>
{|
|[[Image:Select_Project_Type_Calibration.png|center|400px]]
|[[Image:Calibration_Select_Camera_FOV.png|center|400px]]
|}
</center>
* Adjust the [[Region-of-Interest]] to cover the part of video that contains the glowing marker (3).
* Normally, you need to use default calibration settings
** Auto-detect initial camera positions turned on
*** If calibration fails to detect initial camera positions correctly, you can turn this checkbox off and set camera positions manually. But in most cases it will be easier to re-record calibration sequence.
** Auto-adjust camera FOV turned off
*** Use this mode only if you do not use Sony PS3 Eye camera and do not know camera field of view
** '''Regular''' calibration mode
*** In rare cases when '''Regular''' mode fails to calibrate, you can use '''Extended''' and '''Extreme''' calibration modes. It will take much more time, but may help to calibrate correctly if you have high percent of marker misdetections. Usually this is caused by incorrect camera positioning or poor lighting conditions
* Click '''Calibrate''' button and wait while the system finishes calibration (4).

=== Step 6: Check Calibration Quality ===

Resulting scene should look like this:

[[File:Calibration_result1.png|center|800px]]

Make sure you have <span style="color:white; background:#ffd700; padding:5px;">Good</span> or <span style="color:white; background:#8cbf26; padding:5px;">Perfect</span> calibration result.
{{Important|1=<span style="color:white; background:#e93f3f; padding:5px;">Failed</span> calibration is not recommended to use, as you will not be able to get accurate tracking results. However, sometimes '''Failed''' status can be misdetected. If detected marker positions are close to marker image on video in all frames for all sensors, you can use this calibration for tracking.}}

=== Step 7: Check Ground Plane ===
[[Image:Floor-Detection-1.png|thumb|Manual Floor Detection]]
Ground plane should be detected automatically. Ground points are marked by <span style="color:white; background:#ffd700; padding:5px;">yellow</span> color. 
* Make sure that ground points are actually near the ground plane.
* If ground plane is detected incorrectly, select ground points manually.
** Expand '''Manual Calibration Adjustments" expander 
** First, unmark all ground points by pressing '''Clear all points''' button.
** For each ground point, click on it in 3D view and press '''Mark as ground''' button.
** You can cancel marking point as ground point by pressing '''Unmark ground''' button.

{{Important|If you do not mark ground points then the ground plane is incorrect and there is no sense in using Foot tracking option and camera heights values.}}

=== Step 8: Set Scene Scale Using Сamera Height as Reference ===

Now cameras in your scene are properly oriented relative to other cameras and relative to ground plane. But you still need to find one more parameter: scene scale. 

Use '''Сamera #1''' height over ground to set correct scene scale. 

[[File:Calibration_scale1.png|center|800px]]
 
* Save results to calibration project file or using '''Save scene...''' button on '''Scene''' tab (6).
[[Image:Depth_Project_Scene_Tab.png|center|link=]]