What is 3D Scanning?
A common trope in spy and heist movies is for the protagonist to scan the face of an opposing agent or any valuable item and create a perfect replica out of the scanned model. These movies probably take a few liberties for the sake of storytelling, but technology in the real world isn’t that far off from what these cinematic spies can do. Specifically, 3D scanning technology has been around for decades and is widely used across several different industries. How does this seemingly magical technology work? What can be achieved with 3D scanning and how much potential does it have?
What is 3D scanning?
3D scanning refers to any form of technology or technique that collects data from real-world objects or environments and uses this data to construct digital 3D models. Development of 3D scanning technology started as far back as the 1960s in the field of research and design. Early 3D scanners used a rudimentary setup of a combination of lights, cameras, and projectors to accurately recreate the surface of various objects and places.
After 1985, developments in 3D scanning technology allowed for the use of scanners that utilized white light and lasers to capture a given surface. Still, the time and effort needed to create an accurate model proved to be difficult hurdles for the acceptance of 3D scanning technology.
The advent of computers with vast data processing capabilities revolutionized the field of 3D scanning. Fast and accurate scanning of very detailed objects became possible, which led to the development of different 3D scanning techniques.
Nowadays, 3D scanning technology has become heavily used in the entertainment industry in the production of animation, movies, and video games. Consumer-level products that feature motion capture and gesture recognition capabilities have also benefited from the strides that 3D scanning technology has taken in the past decades. 3D scanning has become very useful in industrial design, rapid prototyping, and reverse engineering.
How does 3D scanning work?
Over the years, different techniques have been developed to generate the unique data needed to create 3D models. In a nutshell, all 3D models are essentially “data clouds” – conglomerations of data points arranged in three-dimensional space. Listed below are the different techniques used to create these data clouds:
1. Contact-based
One of the earliest methods of 3D scanning, contact-based 3D scanners rely on very precise measurements of the object made by an articulated arm equipped with high precision sensors. In this method, the object needs to be on a precision flat surface or held in place by a precisely measured fixture. Contact-based 3D scanners are fairly simple and inexpensive. However, they are also relatively slow compared to other scanners.
Another limitation of contact-based scanners comes from the very fact that the probe needs to come into direct contact with the object. This might not be advisable when scanning valuable objects such as historical artifacts. Contact-based scanners are also limited in terms of the size of objects that it can scan since it relies on a platform and articulated arm that has spatial limitations.
2. Photogrammetry
Photogrammetry is a very common method to create 3D models due to its simplicity and versatility. This is a passive method – meaning that it relies only on the energy emitted by the object being scanned. In this case, photogrammetry relies on the visible colors being reflected off the object. Simply put, photogrammetry relies on a series of overlapping photos to come up with a 3D model.
By combining images of an object captured at different angles and matching points between different images to identify features, a 3D model can be constructed without any sophisticated equipment. This level of accessibility is the biggest advantage of photogrammetry as any high-quality camera can be used, even the one on your smartphone. This technique instead relies on an intelligent software algorithm to find the edges of the object, identify matching features, and reconstruct the pixels in 3D space.
Another huge benefit of photogrammetry is that it can capture surface data on top of spatial data. This means that 3D models can be constructed that retain the color or patterns on the surface of the original object. Photogrammetry can also be used to scan huge objects – one of its most common applications is in creating 3D topographical maps of entire landscapes or cityscapes.
The limitation of photogrammetry comes from the fact that it relies on visible colors. Thus, it cannot be used reliably in dark areas or areas with a lot of canopy cover. Reflective surfaces or objects with features that do not have a high contrast can also be particularly problematic. Moreover, photogrammetry is known to be less consistent and accurate compared to other non-contact 3D scanning methods.
3. Laser triangulation
Laser triangulation is only one of several active 3D scanning methods that use laser emissions in various inventive ways. In laser triangulation, a laser is aimed at the subject while a camera records the location of the emitted laser. As the laser hits different features of the subject, the emitted point appears in different locations from the perspective of the camera.
By combining the geometrical data related to the position of the laser emitter and the subject and the angle of the camera with respect to the laser dot as it appears on the subject, the features and dimensions of the subject can be recreated in a digital model. The technique is called “triangulation” because the position of the laser emitter, the camera, and the laser dot on the subject forms a triangle which acts the basis of all spatial measurements. A laser stripe can also be used instead of a single laser point to speed up the process.
Laser triangulation is one of the most accurate 3D scanning methods, able to achieve an accuracy in the order of tens of micrometers. Since laser triangulation also uses a camera, the visual data can be combined with the data cloud to come out with full-color 3D models.
The technology behind laser triangulation is fairly simple, allowing the development of handheld 3D scanners. These desktop-scale DIY models also come fairly cheap – just about a few hundred bucks. Combined with the accuracy and rate of data acquisition of laser triangulation scanners, their level of accessibility has made them extremely popular.
The limitation of laser triangulation lies in the distance. Since the camera needs to see the position of a very small laser dot or a thin laser stripe, laser triangulation cannot be used to scan objects more than a few meters away. Since the method relies on a reflected laser dot, subjects with reflective or transparent surfaces can be particularly problematic.
4. Structured light
Structured light 3D scanners project an image with a pre-determined pattern on the subject. Depending on the features of the subject, the pattern will then be distorted in a number of different ways. A camera records the image of the projected pattern and uses the data on the distortions to calculate the dimensions of the individual features.
One strength of the structured light method is that it does not rely on any sophisticated equipment. The light pattern can be projected on the subject using a standard LCD projector, while images can be captured using any high-quality camera. The speed of data acquisition using structured light is almost unmatched since it can scan multiple points or an entire field of view at once. Resolution is also excellent – typically in the range of 1 micrometer.
As with any 3D scanning method that relies on optical properties, reflective or transparent surfaces can be challenging for structured light 3D scanners. In some cases, this limitation can be overcome by painting over these surfaces with a thin opaque lacquer.
More recent developments in the field of structured light 3D scanning have focused on coming up with algorithms by re-designing the illumination patterns that come up when scanning optically complex subjects. The results of these efforts have been promising for scanning difficulty objects such as reflective metals or translucent surfaces.
5. Time-of-flight
Time-of-flight 3D scanning is another active method that uses a laser emitter to fire off successive pulses of laser light. These pulses are reflected off the surface of the subject, upon which a separate lase sensor receives them. The time interval between the emission of the laser and the reception of the reflected beam is used to measure the dimension of individual features on the surface of the subject.
Time-of-flight 3D scanners have the distinct advantage of being usable over large distances. Light Detection and Ranging (LiDAR) sensors that are founded on the principle of time-of-flight 3D scanning have been extensively used to create 3D topographical maps using an aircraft-mounted sensor. Large structures, such as building and other geographical features, are also commonly scanned using time-of-flight methods. Since time-of-flight 3D scanners don’t rely on visible light, they can be used to scan objects and environments even in darkness.
Data acquisition rate is one of the areas where time-of-flight 3D scanners suffer. Since they only detect the distance of one point at a time, it can take millions of data points to come up with an accurate model of a moderately-sized subject. Some time-of-flight 3D scanners have solved this problem by extending the field of the view of the range finder.
While there are other 3D scanning methods beyond those included in this list, the ones listed above are the most common. Each method has a set of strengths and limitations in terms of data scope, quality, accuracy, acquisition speed, and applicability.
Applications of 3D scanning
As you can imagine, 3D scanning has a lot of potential to change the way things are done across different industries. The applications of 3D scanning in today’s world are incredibly diverse and showcase just how useful and versatile the technology is.
1. Industrial design
Designing new products and prototype has never been easier before the dawn of 3D scanning and modeling. Often, products need to be designed to work around existing objects or environments. By capturing accurate measurements of these objects, prototypes can be created that fit perfectly to their applications.
Reverse engineering a physical object has also become much easier with 3D scanning technology. A digital model of an object can be generated with extremely high accuracy, allowing for mass-scale reproduction. The 3D model can even be tweaked to implement easy improvements.
2. Entertainment
Motion capture and recreation of real-world objects in a digital space have become incredibly common in movies and video games. This is made possible by a variety of different 3D scanning techniques that can capture motion paths or even recreate human faces. Computer-animated models typically begin with hand-sculpted physical models that are then scanned and manipulated in a digital environment.
3. Manufacturing
3D scanning has allowed manufacturing and production firms to monitor the quality of tools and manufactured products with utmost precision. “Hand-tuned” products can be 3D scanned to generate a model that will act as the basis for mass production. Tool and equipment wear can also be monitored at a high level of detail, giving firms a chance to reduce the likelihood of equipment failure.
4. Construction and civil works
The construction industry may be one of the biggest beneficiaries of 3D scanning technology. From site modeling to monitoring of progress and quality control, 3D scanning can be used in a huge number of ways to model and assess any major construction work. 3D scanning can also be used to establish a “benchmark” for a newly constructed building, making it much easier to identify deformations in the structure as a result of extreme conditions.
5. Archeology and geology
The technology of 3D scanners has been used in combination with drones to create topographical models of unexplored lands. With the ability of some 3D scanning methods to penetrate foliage and other canopy cover, 3D scanners have even uncovered networks of cities and roads that are invisible to the naked eye. For geologists planning expeditions and surveys into the unknown, 3D scanning has proven to be an invaluable tool for planning and reconnaissance.
6. Real estate
Some enterprising real estate agents have come up with the bright idea of using 3D scanning technology to offer virtual tours of their property to prospective buyers. This is a level of immersive marketing that beats anything that photos and videos can offer, all without the hassle of driving over to the actual property.
7. Preservation of art and artifacts
3D scanning has allowed archeologists, historians, and museum curators the ability to preserve historical artifacts in a digital environment. The technology has even provided them the opportunity to intimately analyze these artifacts without risking permanent damage. Some museums have leveraged the use of 3D scanning to allow visitors to interact and view art pieces and artifacts like never before.
The future of 3D scanning
1. Mobile photogrammetry
One of the most exciting frontiers in 3D scanning is the possibility of being able to do 3D scans using your typical smartphone. Since it’s impractical and expensive to equip a smartphone with additional dedicated sensors, photogrammetry seems to be the most sensible way to go. Software-driven photogrammetry certainly sounds feasible but taking the right photographs from the right angles requires a certain level of skill which might be off-putting to the casual smartphone user. Most smartphones are also not equipped with enough processing power to handle pixel matching of what could potentially be dozens of individual photographs.
However, it’s only a matter of time before camera and mobile processing technologies catch up to the demands of on-the-go photogrammetry. In fact, iPhone users have been able to do mobile photogrammetry for a few years now through the Trnio app. By providing basic tracking guidance to the user and taking advantage of cloud-based data processing, this simple app has been able to generate basic 3D models, albeit after a lot of waiting due to multiple file transfers.
2. Integration with artificial intelligence
Even with all the sophistication of 3D scanning, it is still a method that relies heavily on human intervention. In particular, the use of 3D scanning for quality in the manufacturing industry still relies on human-decided “pass” or “fail” conditions. This is because letting a part or tool pass the quality standards of the process can be very subjective and can be too complex for a computer to process.
This can all change by integrating artificial intelligence (AI) into the 3D scanning process. A carefully-designed AI can make rapid decisions on quality control using a highly complex set of parameters. This can help streamline the manufacturing processes across several industries and provide a more accurate and less labor-intensive alternative to human-based decision making.
3. Portable, accurate, and affordable 3D scanners
Handheld and portable 3D scanners are actually already available today, but the cheapest models typically fall short in terms of performance. Most 3D scanners in the below $500 range are inaccurate, unreliable, and generally clunky for average users. If you want a high-quality desktop 3D scanner, you are going to have to fork over more than $2000.
If you are dreaming of owning a reliable 3D scanner at a price that won’t break the bank, then the bad news is that the technology isn’t quite there yet. However, the mainstream success of desktop-scale 3D printing means that there is a viable market for casual 3D modelers and DIY creators. With a huge following, it should be only a matter of time before 3D scanners enter the casual or hobbyist market.
Final thoughts
Although 3D scanning technology has been around for decades, it is only recently that huge industries have started to take notice. 3D scanning has a huge number of applications across different industries: prototyping, industrial design, manufacturing, entertainment, construction, and artifact preservation. The existing techniques for 3D scanning are just as varied, with each method having its set of strengths and limitations that make it apt for different circumstances.
There is no doubt that 3D scanning will continue to be a relevant technology and will receive focus in terms of innovation and advancement. 3D scanning technology might even soon be available on the phone in your hand. We believe that 3D scanning still has a lot of untapped potential, and the future is looking very bright for this particular technological marvel.
