BENQ MH630

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  • #100763
    fredjiencke
    Participant

    Hello-

    I am charged with acquiring the parts to build an AR Sandbox. I’m going through the parts, and one that seems relatively simple is the projector.
    I see that the recommended projector is the Benq MX620ST.
    I was looking around and I saw this one on sale:
    Benq MH630.

    Some possibly important information:

    Native Resolution:

    MX620ST: XGA(1024 x 768)
    MH630: Full HD (1024 x 768)

    Lens:

    MX620SX: 4:3
    MH630: 16:9

    Throw Ratio:

    MX620SX: 0.9-1.08 (54.5″±3% @ 1m)
    MH630: 1.15-1.5(78.3″±3% @ 2m)

    Image Size:

    MX620SX: 30″-300″
    MH630: 46″-300″

    I do see that the resolution is controlled by the Kinect unit, so I assume that the higher resolution of the MH630 probably does not play a factor. I don’t know much about the Throw ratio, but a short Throw ratio is required(?)-If not the height of the unit needs to be as wide as the longest sandbox dimension? If this MH630 would work, would this possibly create problems more significant than the MX620ST will? (I suspect that much more work and troubleshooting has been done with the recommended MX620ST).

    There is a high probability that I will be asking more questions in the near future, but whether this MH630 projector will work with this project is the most pressing question at the moment. I’d like to order the projector as soon as possible.

    Will this MH630 work with a sandbox? The MH630 looks to be just a little more expensive as it is on sale for a significant discount.

    Any other suggestions will be much appreciated.

    Thank you very much…

    Fred

    #100764
    fredjiencke
    Participant

    Hello-
    I transcribed the Native Resolution on my first attempt.

    I think this is correct:

    MX620SX: XGA (1024×768)

    MH630: Full HD (1920×1080)

    Thanks,

    Fred

    #100765
    Oliver Kreylos
    Keymaster

    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

    #100782
    fredjiencke
    Participant

    Thanks Oliver.

    Another question about the recommended computer came up. The website says:

    “We recommend an Intel Core i7 CPU (as of 06/2013), an Nvidia GeForce GTX 770 graphics card (as of 06/2013), and the current release of the 64-bit versions of Ubuntu or Fedora Linux.”

    Are there any updates to the recommendations regarding hardware? We would prefer to go with what’s been shown to work. Hopefully this makes any troubleshooting easier and less expensive to the university.

    Thanks,

    Fred

    #100783
    Oliver Kreylos
    Keymaster

    There is a newer graphics card generation, a GeForce GTX 970 instead of the GTX 770 that used to be on the recommended hardware list. We have not tested the 970 yet, but based on its specifications it should be slightly faster than the 770. As it is not much more expensive, it is probably a good deal. We don’t see any reasons why the 970 should cause problems for an AR Sandbox.

    The Intel Core i7 is still the recommended CPU, although a Core i5 should work fine as well. A mid-range i7 (or i5) at a reasonable cost will be ideal; it is not necessary to buy an “extreme edition” CPU or the like.

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