heli

A longterm slitscan of the sky.
Rolled up into a helix to allude to the earth’s rotation and movement through space.

It was born from the obsevation that web cams are not quite static, but “mounted” and moved by the earth.
Yes, related to that infamous GIF.

First iteration made on location in Thallwitz, Sachsen, Germany for MdbK[mobil], recorded between 2019-09-15 14:53:08 and 2019-09-30 11:15:38.


This is an iframe; please use the horizontal scroll bar or swipe.
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The viewer requires a fairly modern browser. If it doesn’t work, check out the simple version below:

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Notes

  • one day = one revolution ⇒ day/night cycle aligns
  • the clouds are curved because of wind
  • the vertical stripes in the center are raindrops on the window that the camera was attached to
  • stripe on the right: the ground, fuzzies on the left: treetops

Documentation

I have also broadcast from the project.

The camera (a simple Logitech web cam). Notice the raindrops.
Three shipping containers housed this group project. You can see the window with the camera through the middle window.
Container und Menschen
The opening ceremony. You can see the camera near the center of the image.
I placed a polarizing filter over the lense to enhance contrast of the sky and also as a ND filter.
On location I had the chance to see the sunrise projected through a keyhole, camera obscura style.

Technical Notes

  • 10264200 slits, 6.2 Gigapixels total
  • 8 slits per second
  • The actual slit-scanner is a fairly simple shell script; ffmpeg, v4l2, imagmagick and some pipes.
  • Another simple script builds the (one-dimensional) tile pyramid.
  • Ran on a Raspi 3B+ and a cheap web host, connected via LTE.
  • three.js does the heavy lifting for the helix viewer. Built in Node with Webpack.
  • I implemented crude LOD algo for the spiral.
  • Possible improvements / bugs / todos:
    • The shading of the spiral looks blocky (even if it is 100% ambient). Either blend or fix the ambient.
    • A live, marching edge would be nice
    • Zoom-out-and-back-in doesn’t land at the same spot.
  • Please contact me if you’re interested in the code.

Thanks

Museum der bildenden Künste Leipzig, the MdbK[mobil] team, especially Manu Washaus.