It's difficult to say what the issue may be with the description and images provided.
Due to the nature of the technology, Ground Plane may not be able to provide 6DoF tracking in all environments. This article includes some information for an ideal Ground Plane environment: https://library.vuforia.com/articles/Training/ground-plane-guide.html
Specifically, the following is relevant to this issue: Ground Plane utilizes images from the device camera to understand the basic geometry of your environment. Therefore it is necessary to stage Ground Plane experiences in settings that enable the camera to accurately capture the details of the surroundings.
- Stable lighting conditions
- Moderate lighting - not too bright or too dark
- Avoid glare and dark shadows
- Surface details help to reveal geometry and improve accuracy and performance
Doing our own experiments, we've found that in areas with low detail surfaces we were able to improve the experience by taking additional time to scan the environment before performing the first hit test. While not guaranteed to work, we were able to perform 6DoF/positional tracking in a wide variety of environments such as low detail carpet, tiles, and pavement.
The basic thought is that the more information the system has from environment scanning (floors, table tops, etc.), the more likely you are to gain a 6DoF pose. You can also use our tracking quality APIs to help better drive feedback to the user to determine the quality of the area you are scanning and allow the app to advise the what steps they can take to improve their experience.: https://library.vuforia.com/content/vuforia-library/en/articles/Solution/tracking-state.html
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