Devon Peet
2D-3D with a Lightning Bolt
Summary
This project explores the area of stereoscopic 3d mapping, specifically developing a depth map from two cameras. In our example, we’ll take two pictures of the same lightning strike and use them to create a 3D render of the lightning itself.
Summary
Our subject is a lightning bolt, effectively a 2 dimensional line moving through a 3 dimensional space. This is a particularly striking example because it allows us to see the twists that look like a simple reversal to one image alone. The pictures were taken at practically the exact same moment, showing the full lightning bolt as it travels to the ground. The pictures were taken from a similar enough vantage point that we can assume that the angular displacement is small compared to the distance. One picture is however much higher than the other, so our stereoscopic displacement will be in the Z plane. This allows us to simplify our function and assume that when a point shifts position in the image, it is proportional to the distance to each camera. We won’t be able to know the proportionality factor through this method, meaning that we are only able to know the relative shifts without having absolute data. Calculating the disparity (in our case the z point), we simply take a point on the left image (x1, y1) and compare it to a point on the right image (x2, y2) and subtract the y values (due to the vertical displacement). This will result in list a points with X, Y, and Z coordinates. This can be plotted in a 3D modelling program (in my case using Python in Blender).
Sources
http://calculatedimages.blogspot.co.uk/2013/05/3d-lightning.html http://stackoverflow.com/questions/6241607/distance-to-the-object-using-stereo-camera http://www.dis.uniroma1.it/~iocchi/stereo/triang.html https://courses.cs.washington.edu/courses/cse455/09wi/Lects/lect16.pdf http://en.wikipedia.org/wiki/3D_reconstruction_from_multiple_images http://www.cse.usf.edu/~r1k/MachineVisionBook/MachineVision.files/MachineVision_Chapter11.pdf http://blender.stackexchange.com/questions/9324/straight-lines-with-no-face-freestyle