3D Scanning and Photogrammetry

In our last article we talked about how someone could take a 3D computer model and turn it into a real object, via 3D printing. This time we’ll talk about how we can take real objects and turn them into computer models, to be used for games or even just to print copies. The method for doing this is called 3D scanning, and it can be done in lots of different ways, which can be broken into three different categories.

The first category involves actually touching the object being scanned. This is most often done using a special machine that touches the object all over, and remembers ever spot it touched. In this way an extremely accurate model of the shape of the object can be created, much like how a blind person can touch an object to know what it’s shaped like. This kind of scanning obviously doesn’t tell you anything about the color of the surface of the object.

The second category is what we would call “active” scanning, which means it involves shooting something at the object to see what bounced off. An active scanner might shoot a laser, or x-rays, or ultrasound. By performing some math on the what bounces off the object, the scanner can figure out where each point on the object is in 3D space. Active scanning is very useful because it can be more accurate than our next category, passive scanning, without touching the object being scanned and risking damaging it.

Passive scanning, our third category, can be most simply described as taking pictures of the object. There are multiple ways of taking these pictures – some involve using multiple cameras at the same time, and some look only at the silhouette of the object from a bunch of different viewpoints, or taking photos with different lighting. Passive scanning is very exciting because it usually doesn’t require any special equipment, just a normal camera.

Photogrammetry is the practice of taking measurements based on photos. It can be used as a form of passive 3D scanning, as well as for many other things, but today we’ll be focusing on the scanning. I want to bring up photogrammetry because anyone with a smartphone can use it to quickly and easily make scans of real-world objects! There are lots of special softwares available for the PC for professional photogrammetry which can be used with photos from any sort of camera, but there are also free software and mobile apps that can give you quite good results.

One that I’ve used myself is called Qlone (no sponsorship), and is available on iOS and Android. You simply print out a piece of paper with a special pattern on it, place your object on the pattern, and take a lot of photos following the instructions in the app. You can look at a bunch of scans made with Qlone right here.

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