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ImageTargets Not Recognised

August 15, 2016 - 1:45am #1

Vuforia SDK Version: 5.5.9 and 6 -
Description with steps to reproduce: We are developing an app where ImageTarget printouts are placed on a white background and detected by a device that is mounted in place.

This works as it should for the most part, but there seems to be a strange behavior where a target can be introduced into view and not detected by Vuforia. When this happens Vuforia seems to refuse to detect the target entirely, even when the target is perfectly in focus and in perfect lighting. The only way of getting Vuforia to detect the target is to completely obscure and then unobscure the target, rapidly change it’s position, or cause the webcam feed to be reestablished by unfocusing and refocusing the app itself.

There are certain cases where a target can be introduce without being detected. These are:
1) Introduced in bad lighting (mottled background / harsh shadows).
2) Introducing the target into the scene at an angle that cannot be detected and very slowly rotating it to face the camera.
3) Introducing the target into the scene fully obscured and very slowly unobscuring it.
4) Rapidly moving the target at a rate at which it cannot be detected, and gradually slowing down to a standstill.

Steps to reproduce:
1) Introduce target without it being detected.
2) Move target around within camera view - it will not be detected.
3) Obscure and unobscure target, or rapidly relocate target - it will be detected.

This seems to occur in both Vuforia 5 and 6.

Is this expected behaviour and / or is there a solution to this issue? -
Development OS (Mac OS X, Windows, Linux): Mac OS X -
Mobile OS and Version: iOS 9.0.2 and Android 6.0 -
Mobile Device Manufacturer and Model name: iPad Air 2 and Huawei P9 Lite -
Do the Vuforia Sample Applications show the same behavior?:

ImageTargets Not Recognised

August 15, 2016 - 3:08pm #2


Currently, there are no known issues in Vuforia 6 with Image Target detection.

It sounds like the base issue is that Vuforia cannot detect a second image after the first. I did a quick mock-up by modifying our Unity ImageTarget sample and was not able to reproduce the issue:


Note that the detection algorithm works best when the target is at a 30-90 degree angle to the camera, and under good lighting conditions with minimal specular reflections. However, once the image is detected and is being tracked, it is much more robust to steep angles, occlusion and specular reflections. This can be clearly seen in the video.

If you still believe there is a regression in Vuforia, please provide a video of the issue by using 'adb shell screenrecord' (Kitkat OS or higher on Android). This will help me to better understand the issue you're observing.


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