This message was posted on behalf of Intel Corporation
Thanks for reaching out!
What camera are you using? The camera with the biggest detection range is the R200 and it is up to 300 cm for hand Blob Segmentation and 500 cm for Person Tracking, as you can see in https://software.intel.com/en-us/articles/intel-realsense-data-ranges.
So, in this case, 6 m would exceed the maximum range for hand tracking of any of the cameras, which in this case would be 300 cm. My best suggestion in this case is that you check the document I shared above and check your camera's maximum range for hand tracking and place your camera a little bit under that limit.
Unity is still supported on the latest version of the SDK, so, you should indeed be able to detect gestures with Unity. You can get more information about the SDK in https://software.intel.com/sites/landingpage/realsense/camera-sdk/v2016r3/documentation/html/index.html?doc_devguide_introduction.html.
I hope this helps.