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Spectacular! 3-D Chalk Drawings

  1. Mar 1, 2006 #1

    Aether

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  2. jcsd
  3. Mar 1, 2006 #2
    Those are stupendous. Particularly that last one.
     
  4. Mar 1, 2006 #3

    Mk

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    Amazing! I had this guy, I think he is even better! I forget his site and his name!! He drew in Italy. Drew for the pope one time I think. Drew things erupting out of the ground and really deep holes. Spectacular.
     
    Last edited: Mar 1, 2006
  5. Mar 1, 2006 #4

    Mk

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    Wow, I found him.
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
     
  6. Mar 1, 2006 #5

    Aether

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    Those really are amazing. What do you mean "I had this guy"? Did you study art under him?
     
  7. Mar 2, 2006 #6

    Mk

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    Oh, no! I had his site bookmarked and I showed it to my friends. If I was a good artist I would want to have this guy teach me!
     
  8. Mar 2, 2006 #7

    Mk

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    I can tell you I would not want to find myself walking over one of his drawings. The holes look so real!! I wouldn't want to stand on the edge either, on one of those drawn rocks. I would freak out. It looks so real...
     
  9. Mar 2, 2006 #8

    Ivan Seeking

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    Absolutely incredible!
     
  10. Mar 2, 2006 #9
    amazing! It only looks like that from that particular angle right? it's just messed if viewed from the side right?
     
  11. Mar 2, 2006 #10
    these are really super neat. you can tell they're drawings, but its so hard to believe they're flat. it would definetly be weird to walk over one. its really crazy.
     
  12. Mar 2, 2006 #11
    linky?????
     
  13. Mar 2, 2006 #12

    chroot

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    Good ol' trompe l'oil. I assume they'll mess with your head if you view them at a time when sunlight is casting real shadows the other direction.

    Related trivia: 90% of normal depth perception is based on information from shadows. Only about 10% is based on real stereoscopic parallax between the two eyes.

    - Warren
     
  14. Mar 2, 2006 #13

    Aether

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    Here's one drawing as seen from the optimal viewing angle:
    [​IMG]

    ...and here's the same drawing as seen from a different angle:
    [​IMG]

    These photos are here: http://users.skynet.be/J.Beever/pave.htm
    I provided this link in the OP, but it has a spurious ':' at the end of the link, and therefore doesn't work. Would someone with the necessary super-powers please fix that link for me? :redface:


    My guess is that they are "designed" for optimal viewing from one particular point in space, and at one particular downward angle (negative elevation) in order to allow the viewer's brain to confuse each pixel's longitudinal distance with its vertical height. I suspect that if you were to project an image (e.g., using a slide projector at night for example) from any suitable point in space (preferably at an average person's eye level I would suppose) and at an appropriate downward angle, then you could use a simple "paint by numbers" approach to chalk-down the drawing. Hehe...now, where do I go to get a grant to take a large GPS-guided farm tractor into the desert southwest somewhere and plough some HUGE mega-artwork (maybe an Egyptian pyramid) into the desert so that from an airliner at 40,000ft it looks like there really is a giant pyramid in the desert.
     
    Last edited: Mar 2, 2006
  15. Mar 2, 2006 #14

    hypnagogue

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    Just curious-- where is this figure coming from? Of course, in addition to shadows and binocular parallax, there are also many other cues we can use to process depth information (e.g. see here).
     
  16. Mar 2, 2006 #15

    chroot

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    Unfortunately, I don't have a link. Due to eye-muscle surgery I had as a child, I have only about 10% of normal stereoscopic depth perception. Several optometrists have told me (and my parents) that it doesn't really matter, because 90% of depth perception is based on visual cues like shadows.

    It's probably not an "exact" figure anyway, even though it's been repeated to me a couple of times. It's probably more like a rule of thumb.

    - Warren
     
  17. Mar 2, 2006 #16
    yeah chroot is right, I have amblyopia in my left eye, so I see 90% out of my right eye which means technically I should have very little depth perception. However my brain has compensated by using other visual cues and systems. And without much problem since I've played active sports all throughout my life.
     
    Last edited: Mar 2, 2006
  18. Mar 2, 2006 #17

    chroot

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    You're lucky you can play sports, Greg! I'm pretty lousy at anything involving flying balls, so I took up rock climbing and scuba diving and cycling instead.

    There's nothing worse than tennis: a small, fluorescent ball, illuminated uniformly by sunlight, high enough in the air that its shadow is impossible to discern. Parallax is the only way to tell where a tennis ball is in mid-air, and I can't do parallax. As a result, I'm probably the world's funniest tennis player. :biggrin:

    - Warren
     
  19. Mar 2, 2006 #18
    That is much more extreme that I imagined. They are pretty much lost from the wrong viewing point. I don't have any idea how they work out what has to be drawn to make it work from the correct angle. There is much more planning to those things than a crop circle.
     
  20. Mar 2, 2006 #19
    Those are incredible!I wonder if there waterproff.
     
  21. Mar 2, 2006 #20
    Monocular Cues

    Several strong monocular cues allow relative distance and depth to be judged. These monocular cues include:

    1. Relative size
    2. Interposition
    3. Linear perspective
    4. Aerial perspective
    5. Light and shade
    6. Monocular movement parallax

    These are very interesting, Hyp, especially the last which I had never noticed, but just checked out and found it to be true: When you move your head things in the distance seem to move slightly in the same direction as head movement. Things close up seem to move opposite to the direction of head movement.

    You'd expect the latter, but not the former.
     
    Last edited: Mar 2, 2006
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