Tracking is what makes zSpace the powerful tool that it is. In this article, I will discuss high level how tracking works and actions a user can take to improve the experience.
The zSpace system uses sensors and infrared light to perform tracking. Because zSpace tracking is using light it can be susceptible to noise from other light sources. This article is applicable to our zSpace System Software 5.0.1 release. At zSpace we are always working to improve the tracking experience.
How tracking works
The zSpace has 4 sensors on the front that emit and receives infrared light. The zSpace glasses have 5 markers which will reflect the light back to the zSpace. The stylus emits an infrared light from each tip and also contains a gyroscope. The zSpace display uses a combination of 4 infrared sensors to track the movement of the eye wear and stylus. All 4 sensors track both the glasses and stylus.
For head tracking to start all 5 markers on the front of the glasses need to be initially seen. After the system has detected the glasses, only 3 of the 5 markers need to remain visible. If all 5 markers remain visible the system can switch between which 3 of 5 markers are being used to track the glasses. Similarly, the stylus uses 2 light points and the gyroscope to initialize tracking but once the stylus is seen 1 marker can be covered and tracking will continue. In fact, both markers can be covered for short periods of time and stylus tracking will continue.
Successful tracking should occur from any location in front of the zSpace where all of the tracking markers on the glasses and/or IR emitters from the stylus can be visibly seen by the tracking sensors. Tracking can be interrupted whenever there is occlusion of these sensors.
One example of this would be holding the stylus under the table the zSpace is sitting on. In a position like this, the tracking sensors are unable to see the emitters and will not be able to track the stylus. Another example is when holding the stylus in your hand, you move your hand in such a way that it “blocks” the glasses. We do go to great lengths to allow tracking to continue when the stylus and glasses are overlapping but it is possible you might see a small pause in tracking as the devices overlap.
Good tracking, what should it look like
In ideal conditions, as long as the glasses or stylus is in the viewable area, tracking will be smooth without hesitation. All five tracking markers will clearly be seen as well as both markers on the stylus. Even small movements of the glasses or stylus will be seen by the system. You should be able to freely move the glasses or stylus within the bounds of the screen at even a few feet distance from the display as long as long as the glasses and stylus are within site of the tracking cameras on the zSpace.
What you can do to improve tracking
We have gone to great lengths to make our system handle different lighting scenarios. Generally speaking, typical home or office lighting will not cause tracking issues. If you find that tracking is not performing well, check your environment around you.
Light sources and moving light sources
Very bright lights may interfere with tracking. Trade shows and conference halls commonly have extreme amounts of lights. Our software has ways to handle this but if the light sources are too extreme or the light sources are moving, there is no workaround. The light source does not necessarily have to be moving. Consider the case where you may have indoor plants between your zSpace and light source. Ventilation systems may blow on the leaves of plants causing them to block and unblock the light. This would make the light appear to be a moving source.
Unseen light sources
It is possible you may have light sources around you which are not easily visible or not visible at all. One example we commonly see is very small but very bright LEDs on computer cases. This problem is exacerbated by the fact that the light source may be shining through the internal fan blades on a PC which would cause the light source to appear to be moving. Infrared devices such as TV remotes or the Microsoft Kinect camera may cause interference as well.
Generally, sunlight is not an issue but early morning or late evening when the sun is low in the sky the sheer size and brightness of the sun may cause issues. This is also true for bright sunlight reflecting in through windows or in a small area with multiple windows.
Rings, watches, jewelry
All of these reflective metallic materials can appear as light sources in the tracking sensors or could reflect light from other sources, including the stylus or the zSpace tracking LED ring of lights. If this occurs, tracking is likely to be working but will potentially appear to intermittently pause because of the interfering light sources. It is recommended to remove or cover jewelry if you suspect this to be a problem in your situation.
Some clothing can cause interference such as safety clothing like what a construction worker might wear or bicyclists might where so cars can see them. The reflective materials in these garments can interfere with the tracking system and should be avoided while using zSpace.
Determining the cause of interference
The first step to diagnosing tracking interference is simply looking around your environment for some of the sources we have already discussed above. Try to get your eyes as close to the sensors on the zSpace as you can and get an idea of what the sensors might be able to see. A helpful tool is to use a camera, place it in front of the sensors, and take a picture. Sometimes cameras will show light in a different way than our eyes.
Sometimes simply moving the zSpace to a new location or changing the orientation of it in the room is all that is needed to reduce or resolve lighting issues. If your tracking is working after the re-orientation, you should be able to isolate the cause of the interference.
If you find tracking is not working well for you but works well for others on the same system, this could be a sign that interference has something to do with your clothing, prescription glasses or jewelry. Try covering your body with a towel or blanket and removing any jewelry you can.
zSpace units sitting side by side
When zSpace units are sitting side by side it is possible the units are able to see each other. The Infrared from one unit could affect a unit on either side. Additionally, the zSpace could potentially see the user of a system to the side. For this reason, we have made invisible “walls”. The way this works is we are able to see the distance a user is from a system. If a user appears to be to the side we ignore that target.
Share your experience with interference
We are always looking for ways to improve our tracking. If you do have a unique environment and tracking is not working well, please tell us about it by sending an email to firstname.lastname@example.org. Please take pictures and describe the light sources as well if possible.