Lightning strikes thrice: How one man turned two different photos into a 3D model of a lightning bolt
posted Tuesday, May 14, 2013 at 12:45 PM EDT
The internet is a big place, and sometimes crazy coincidences manage to occur. Like two Redditors in Denver who both managed to snap a photo of the same lightning bolt at the same time -- and then a third one using those pictures to extrapolate a 3D rendering of the lightning.
As explained in his blog post, Richard Wheeler noticed the pair of images, and decided to reconstruct its path in 3D. The images were taken from very similar directions, but at different heights. He then resized the lightning bolt images to make them approximately the same size, and then charted the coordinates of a series of points along the length of the bolt. From this, Wheeler calculated the difference between the two angles, and triangulated the 3D projection of how the bolt would have looked. By his own admission, it's "slightly more art than science." As he explains it:
Now we need to do some maths... except I don't like doing complicated maths and it turns out there is a big simplification you can make! If both pictures are taken from a long way away from the lightning bolt (i.e. the object has quite a small angular size in the image) then the shift in position between the images is proportional to the distance from the camera. Bigger shifts mean that bit of the bolt is closer to the camera. This approximation is pretty accurate for the majority of cameras, so I used it here.
The other problem is the proportionality factor. If one part of the lightning bolt shifts twice as much between the two images as another part that means it is twice as close. But twice as close as what? Without knowing exactly where the cameras were positioned that means only the relative distance, not absolute distance, can be calculated. Oh well, close enough!
The result? You can see his final 3D rendering in the GIF below -- and it looks just about exactly how you'd expect a 3D lightning bolt to look. Which makes us wonder if you could do this with a larger number of cameras all recording storms, and get a more accurate look at how lightning behaves in three dimensions.