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Projecting Data on a Sphere

Posted by ryuzaki0 on from the higher-def dept.

necro81 writes "The NYTimes has an article in today's Science section that describes a four-projector system that displays images on a spherical screen. The Science on a Sphere system, developed at the Goddard Space Flight Center and used in some planetariums, can display and animate vast amounts of visual data from the Earth, Moon, Sun, and the other planets. The sphere is suspended by thin wires, and animating the image data gives the illusion of a free-floating, rotating world."

9 of 139 comments (clear)

  1. why not from inside-out? by WinEveryGame · · Score: 4, Insightful
    Isn't best projection on a sphere done from the center of the sphere?

    Since the application of this thing can easily require building a custom sphere, this seems a more cost-effective way to me.

    1. Re:why not from inside-out? by Anonymous Coward · · Score: 2, Insightful

      Since the application of this thing can easily require building a custom sphere, this seems a more cost-effective way to me.

      Assuming a requirement was the ability to hang the sphere to make it appear to float, then you'd have to figure out a way to have a fairly strong internal structure to support the projectors without creating seams from within the structure itself. Also you need to get power and video signals to the projectors and still keep your "disappearingly thin wires". Then there is always the major issue of cooling the major heat generating projectors within a sealed environment.

      Not that these issues can't be addressed, it's just that it comes down to just what you said, being "cost effective".

    2. Re:why not from inside-out? by Chirs · · Score: 3, Insightful

      How would you support the translucent screen? Any structural members would cast shadows.

    3. Re:why not from inside-out? by Anonymous Coward · · Score: 1, Insightful

      I don't pretend to understand anything about this, but the most logical way to project from inside a sphere would probably be a spherical projector. The problem with that being that there would be a distinct loss of resolution as the distance increased from the projector to the screen or area of the projection. If you project from the outside this loss is reduced as you don't have to deal with the reverse conelike nature of the projection from inside the sphere. In other words, the distance between single degree changes between increasing distances would no longer be a problem if projected on from the outside using overlapping projectors.

      Er.. something like that?

  2. Re:Perfect for mission briefings by Tackhead · · Score: 3, Insightful
    > That's just what I need to show my pilots where the shield generator is located.

    It's a planetarium turned inside-out. Or the offspring of a mating of a planetarium and a Klein bottle. In other words, it's a light trap :)

  3. Re:Shouldn't they be able to do with 2 projectors? by Anonymous Coward · · Score: 1, Insightful

    .. and that's the best-case when you have the projectors positioned at infinity!

    If you have them any closer than infinity, then the equator will be in a shadow. Unless you cheat and have a slightly non-spherical globe.

  4. Re:suspended by thin wires by MustardMan · · Score: 3, Insightful

    Either of those options is gonna be some sort of elastic force - the sphere will bounce. Even a slight bounce in a normal projector screen is quite noticable. I can only imagine it would be a lot worse when you're worrying about the alignment of three projectors.

  5. Doesn't that making zooming in unrealistic? by Retired+Replicant · · Score: 2, Insightful

    The cool think about something like Google Earth is how you can zoom way in to see tiny details. If the display is an actual sphere, wouldn't you be kind of limited in showing anything at a scale other than that which can be represented on a physical sphere the size of the projector-screen?

  6. Re:Shouldn't they be able to do with 2 projectors? by Anonymous Coward · · Score: 1, Insightful

    In other words, the North Star, which is quite close to being directly overhead at the north pole, is not visible from about 10 degrees north latitude to the equator. Sailors know this very well.

    And Polaris is 430 LIGHT YEARS away, or more than umpty-jillion Earth diameters. If your sphere were the size of a beach ball, the projectors could be REALLY FUCKING FAR away, and there would still be a three-inch band of darkness around the middle.

    (I got too lazy to finish working out the math.)