How would one go about generating such a thing from an existing object lacking schematics?
Edit: …in an automated fashion. For example, is there an app where I can put an object on a turn-table, point my phone at it, and give it a spin? (Clearly that would work only for certain shapes.)
> You can, if course, just measure and draw it out yourself. But the rounded sides are likely going to be guesses.
Use a caliper measuring device and a flatbed scanner.
With the flatbed scanner, make a high res (600 dpi, or maybe even 1200 dpi) 2D scan of the front of the phone. Keep the screen of the phone on while scanning, and have it display some image that contrasts well against the edges of the screen, so you can clearly see where the edges are. (Ie if the phone is black or other dark color, use a an all white image. If the phone is a bright color, use a dark image.)
Scan the back of the phone as well, so you can see where the camera lenses on the back of the phone are.
Import the 2D images into your 3D modeling software of choice and create a flat polygon covering the front view. Extrude into a 3D shape.
Scale according to physical width, height and depth of the phone that you measure with the caliper.
Make room for the lenses using the scan of the back of the phone.
Buttons on the side and charging port on the bottom you can decide on how to fit from using caliper measurements, and adding some additional room around those as that is often desired.
Then model a shell that fits around it.
It will probably take a couple of test prints and refinements to get it right even so, but I think said approach will work well in terms of benefit to effort.
If you’ve got curved edges that matter (my iPhone13 doesn’t, but my PinePhone does), it might be worth trying to get a good end-on cross section photo, and importing that into a 2D drawing tool you can use to create that shape in a format your 3D modelling tool can extrude. Looking at my PinePhone, and thinking in OpenSCAD terms, I’d probably model the phone as an intersection of two extruded objects one from the end and one from the side, where the 2D shapes I’m extruding would be as close as I could get to end and side profiles, then use rotate-extrude to make the rounded corners (these look “circular enough” for that, if they were more elliptical, it resize the circular extrusions to suit).
That’d work pretty well for phones (like the PinePhone) that are basically “rectangular prism slabs with uniformly rounded edges and corners”. It’d be much harder to model this Samsung S4 I have here, with its curved ends and it’s compound curved back…
The industry standard for manufacturing would be a CMM. Good ones quickly get you micron level resolution. Newer units will laser scan every surface and output a model. Older models physically probe the features. They are mostly used for checking a product vs its CAD design, but they can be used for data acquisition. They pair well with photogrammetry.
Take a photo of the object from all angles, I usually end up with 40 photos. Don't move or spin the object, the static background details help align the images and you want the lighting to be consistent. Smartphone cameras actually work best for small objects because their tiny aperature keeps everything in focus.
I've used the turntable laser scanners (NextEngine specifically) but it is far from automated, requires hand alignment of point clouds. Photogrammetry approach was much lower effort.
But really this gives you a mesh, which is far from being a CAD drawing. Taking measurements and drawing from scratch is usually how I've seen it done when accuracy matters.
3D scanners do exist, though in my experience their performance is very poor and requires lots of manual post-processing to get a reasonable model out the other end. They're also quite expensive, generally.
You touch the object in as many points as you need and translate the touch coordinates from the angles of your tool's arm to XYZ. Or some systems allow you to do it optically.
I've worked with these, they are super cool. Just the laser part of the hand-held scanner was detailed enough to show the lettering on a laptop keyboard because of the differing depth of the molded-in characters.
As the other comments here have already mentioned, automated methods are available but expensive and relatively low accuracy. I'll add that manually measuring parts with instruments like calipers or micrometers in order to reproduce them is common in the machinery industry.
I’m hoping some of the mobile app 3D scanning software starts to take full advantage of the TOF laser dot point sensors available on current flagship phones, and fusing that point cloud data with the cameras and gyro/accelerometer data as you wave the phone around scanning the object. (That was a big reason behind me upgrading to an iPhone13Pro.)
Edit: …in an automated fashion. For example, is there an app where I can put an object on a turn-table, point my phone at it, and give it a spin? (Clearly that would work only for certain shapes.)