In this tutorial, Nick Lievendag contributes to our series of photogrammetry tutorials. Today he breaks down the tools that are helpful for creating high-quality photogrammetry and 3D scans.
1. A Light Kit
While industrial-grade 3D Scanners usually have a build in LED light source, affordable ones haven’t. This means the scan quality will greatly depend on the lighting conditions. For photogrammetry the solution is simple: capture your subject outdoors, preferably on an overcast day for nice, diffuse lighting. If you have a 3D scanner that projects a visible line of laser light, scanning outside might also work. But if your scanner uses invisible, infrared light, you’re bound to scan indoors.
But in many cases you’ll want to scan indoors anyway to keep control of the lighting. In this case it’s wise to invest in a studio light setup. Not flash lights for photography, but permanent lights used for video production. The kits usually come with 3 lights with softboxes on stands. Depending on your budget, you can buy a kit with LED lights or a more affordable version with fluorescent bulbs. The amount of light you need depends on what you want to capture. Just be sure the light temperature is 5500 Kelvin (daylight).
I have two kits: one very portable (they usually come with a carrying bag) one with three 65 Watts bulbs and small umbrella-style softboxes. It’s good for scanning small objects like the Teddy Bear you see a lot on my blog. Mine was off-brand and about €200.
I also have a larger kit from Bresser that can hold 5 separately switchable bulbs, totaling 2500 Watts of light. It comes with a bag, but I call it the Body Bag for a reason. That’s why I only use this set in my studio only and usually for Full Body Scanning. I might swap that kit for an LED version one day, because that would be a lot lighter and would save a lot of electricity as well.
If you want go totally portable though and use a Structure Sensor, you can also buy a small LED light that you can stick onto the back of the iPad or plug into the headphone port. This does help in some unplanned scenarios where lighting is simply bad. I always have my Structure Sensor and one of these in my bag. It isn’t perfect, because color textures are usually captured at a wider angle than a light like this can cover and you’ll have to keep a fixed distance from your subject to avoid even more lighting inconsistencies. But it’s better than nothing.
2. A Turntable
Using a turntable has the big advantage of not having to walk around the subject. This means you’ll need less space and less lights and in some cases your 3D scanner can even be mounted in a fixed position. As a 3D (Scanning) Consultant, I do a lot of research on the technology and have come to know a great lot of people involved in it. One thing that I noticed is that almost every one of them owns a €6,99 IKEA SNUDDA Lazy Susan Turntable. And though none of them seem to be perfectly centered (I tested 20 last week…), I use mine a lot to scan small objects.
If you want to scan bigger objects or humans, you’ll have to buy something more serious. I own an electric turntable manufactured by Dutch company Pre-Motion, that can hold up to 100 kilograms. They have two versions with different fixed speeds and I tested both to discover that the slowest 0.8 RPM version works great for 3D Scanning. I modded mine by adding a simple foot-operated light switch in the power cord, so I can take my time to scan the front and head of people first and then turn on the turntable with my foot to capture the rest at a comfortable pace (the GIF below is played at 4x the original speed). A turntable like this isn’t very cheap and also isn’t very light (15.5 kilograms), but if you’re going to put people on something that rotates it better be good, right?
To stitch geometry from different angles together into one seamless model, all 3D capturing software use feature detection and tracking to understand which parts need to go where. Some 3D scan solutions use just the geometric features (from the black-and-white Depth Map) for this, while others also use the color information for this (referred to as RGB+Depth tracking). This means that the former method will not be able to capture perfectly smooth globe because of the uniform geometry of a sphere, but the latter can, because it detects unique features of the print.
Ford RGB+Depth scanning, you can solve most tracking problems by adding distinct visual features to your object. Some scanners come with dedicated marker stickers for this, but most of them usually detect any high-contrast stickers. I always have a few packs of small fluorescent stickers from Avery that you can buy in any office store. If you want to capture color as well as shape, just place the markers strategically so you can easily remove them from the texture map in photo editing software. Photoshop’s Healing Brush works pretty quick for this in most cases.
4. Matting Spray
Both 3D scanning hardware and Photogrammetry-based software solutions rely on computer vision of some kind. They either project visible or invisible light onto an object and capture the result with a camera, or they use software algorithms to estimate depth from images. In all cases, the computer tries to understand what it’s seeing. And computers aren’t smart enough yet to understand a few surface types that humans take for granted: transparency and specularity.
This basically means that see-through and shiny objects cannot be 3D captured in their original state. But if you’re just caring about the geometric shape and not the esthetics, there is a solution for this: making the object opaque and matte. This can be done using a a matte, light-colored spray. And in most cases probably temporary. There are special 3D Scanning Sprays on the market, but there are many cheap sprays that will do. From chalk spray to water-soluble glue spray or even hairspray. Just make sure you don’t use any of them on sensitive materials.
If you want to scan people, you will run into problems with people wearing shiny things like glasses. If you need a 3D model of a person that always wears glasses, you can scan them without their spectacles on and add these in post production. For this you will naturally need a 3D model of the glasses, and 3D scanning them separately is very hard. Luckily, you can find many brands and models on 3D Stock websites like Turbosquid for a reasonable price. Just be sure the file format is compatible with the 3D modeling software you intend to use.
5. Good Software
Some 3D Scanners only work with the proprietary software that comes with them, but affordable depth sensors like Structure Sensor, Microsoft Kinect or scanners based on Intel’s RealSense hardware can be used with a variety of software.
For example, while reviewing the Structure Sensor, I discovered that the third-party iPad app itSeez3D works better for scanning people, while the Scanner App from the device’s manufacturer offers more flexibility for scanning objects. And if you wan’t to have a lot more control, you use the Structure Sensor to wirelessly transfer its data from the iPad to the Scanect software for Mac and PC, which I’m currently testing a new beta version of. This software offers a lot of professional (there’s a Free and Pro version) scanning and post production features and also works with a lot of other depth sensors, like the Microsoft Kinect or the Apple-owned (but discontinued) PrimeSense Carmine.
For Intel RealSense-based 3D Scanners, like the XYZ 3D Scanner I reviewed recently, I discovered that the Free Sense for RealSense software made by 3D Systems offers a decent set of options for both scanning and post production that might be attractive for beginners.
For Photogrammetry there are a lot of options as well and most offer a free version or trial so you can test the results. If you want to go completely free and mobile, you can start by trying these free smartphone apps.
6. A Sketchfab Account
If you want to share your 3D Scans with the world (and don’t have the cash to 3D print all your scans and mail them to your friends and family), there’s only one way to do it in style: Sketchfab. The website has quickly become the YouTube of 3D Models and offers an easy-to-use way to publish and share your 3D scans through the web, social media and even in Virtual Reality. Manually uploading scans isn’t necessary in most cases, because almost every 3D scanning and photogrammetry software can directly publish the result to your Sketchfab account.
It’s free, but I can totally recommend the Pro account if you’re taking yourself and your work seriously (and want to support the development of this great service). The Pro features I use the most (Yes! You can also follow me on Sketchfab) are the ability to publish models privately and change the background to something more branded. Also, some of my scans go beyond the 50MB file size limit of the Free version.
The statue above is captured through Photogrammetry using a Sony RX100 M2 camera (on a monopod) and the Autodesk ReMake Software I’ll be reviewing soon.