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Thread: lets make an animated "crystal ball"

  1. #1
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    Default lets make an animated "crystal ball"

    EDIT: The way some of the members here have desperately tried to identify my location and nationality for whatever reason they believed was needed for by asking an admin to check my profile logs and researching me by the content of my posts has been very creepy and unnecessary. So bye.
    Last edited by dream; 04-28-2016 at 16:22.

  2. #2
    mixedgas's Avatar
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    . Frost ball using very fine silica dioxide (cabosil) mixed in a varnish binder.
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    Gently sandblast inside of ball with very fine abrasive.
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    Sand inside of ball with #600 wet silicon carbide sandpaper (tedious)
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    Find can of translucent spray privacy paint jar or translucent paint at art store.
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    Find Jewler's Rouge or Lapidary Abrasive and scratch inside of dome. Opticians that actually make eye glasses, may have the abrasives.
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    Water Glass, (Sodium Silicate in water used for preserving eggs) mixed with fine white sand
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    Varnish mixed with fine white sand.

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    Worse case, find a glass installer or university chemist and ask them to Frost ball in very weak Hydrofluoric Acid (HF ) etching crème (Note HF is very dangerous, corrodes your nearest bones to dust if you get it on your skin, must use heavy rubber gloves and safety glasses )

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    A very serious car parts place might have the abrasive for lapping valve seats.
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    All of the above are what I can think of that will do this. I don't know if any of them are available in your area.

    Steve
    Qui habet Christos, habet Vitam!
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  3. #3
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    I'd try dulling spray from the art store, used to give artwork a matte finish. The globe you tried failed because the diffusion goes all the way through the thickness of the material. No good.

  4. #4
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    I'd try a lighting store, or anywhere they sell replacement shades for lighting fixtures. Clear globes arre common.

  5. #5
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    If you use a fisheye lense, you have to pre-distord (spherical projection) your video footage. Convert your x,y video pixel to latitude/longitude coord.

    Fred.

  6. #6
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    a solution of NaOH and MEOH will etch the glass and is safer than HF. Here's the laymans version. Get a 5 gallon bucket and dump in a can of draino. Fill up bucket 1/4 full of water and stir with wood or plastic rod NO METAL. once the now hot foaming solution is done and the liquid is clear IE all the crystals have dissolved. Dump in a liter or two of methanol or ethanol. Don't use rubbing alcohol. This is the same bath used in chemistry labs to clean glass ware. Generally you only leave it in the bath for a few hours. If you leave it over night it will etch and frost the glass. Add a fishtank pump to keep the solution moving of the frost will not be uniform.

    Chemist version. make a saturate solution of sodium or potassium hydroxide. Add in 20-40% primary alcohol in a plastic bucket. Add stirring bar or elevated stir device. Add glassware and cap bucket. Remove in 2-4 hours. Rinse in DI water.

    Another way of doing what you want is to make a bar of pixels that fits the glass globe. Spin it and the line will be made to read out the image. Resolution is limited by the number of pixels in the bar and how fast you spin it.

  7. #7
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    try a lens from a go pro. one feature I hate from them is the fish eye. also how about a peep hole lens from a hotel door. I think pangolin makes such a lens too.

  8. #8
    mixedgas's Avatar
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    Pangolin's lens is not a classical "Fisheye". The lens design is offset to compensate for the fact that the beam from the scanners is a essentially a point source, not a flat plane like a CCD. Light from the projector would never focus properly. In optics terms the "entrance pupil" on the Pangolin Lens is probably too small for video. (my best guess on the technical part) I own one and I just ran a quick test. So that's out as Dream can't add a second relay lens to compensate.

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    But hope is not lost...........

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    Here is the web site for the manufacturer of the lens listed by the maker types:

    http://opteka.com



    Steve
    Last edited by mixedgas; 08-17-2015 at 11:27.
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  9. #9
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    the nikon fisheye lenses actually work really well.
    I believe I have FC-E8

  10. #10
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    Ow sorry not sure with video projectors. With laser for sure though!
    *and yes that first one is the one I have* I got it for less locally though.. got lucky.

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