Reply To: BENQ MH630

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Oliver Kreylos

The Kinect camera has a 4×3 aspect ratio, meaning that the sandbox itself should ideally also have a 4×3 aspect ratio, or there will be parts of it that won’t be scanned, and that would be confusing/irritating.

This projector has a 16:9 aspect ratio, meaning that it would have to over-project the area scanned by the Kinect. This is not necessarily a problem, but it will take some extra software setup to ensure that the overprojected parts are black, to be close to invisible, instead of some random color. When overprojecting to the full size of the scanned sandbox area, the remaining resolution of the projector would be 1440×1080, which is somewhat higher than the 620’s 1024×768. But the sandbox’s effective resolution is limited by the Kinect camera’s 640×480, so the benefit would be marginal.

The bigger issue is throw distance. The 620’s throw ratio matches that of the Kinect camera, meaning it can be mounted at the same height as the Kinect. This projector needs to be mounted significantly higher to achieve the same projection size, which makes the overall sandbox design more complex (probably needs a mirror), and could potentially lead to problems when the Kinect itself ends up in the projector’s light path and casts a shadow onto the sand surface.

Based on the projector specs and the throw distance calculator at Projector Central, the minimal throw distance to create a 30″ tall image is 61″.

Here is an existing AR Sandbox installation with a long-throw projector and a mirror: British Geological Survey

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