The Pros and Cons of Photogrammetry vs. 3D Scanning for 3D Printed Figurines
3D printing and digital 3D replication technologies have existed for nearly a decade and been used in a complementary fashion for a variety of professional and industrial applications, such as reverse engineering and digital archiving. Yet it’s only been in the last few years that we’ve seen a growth in these technologies used together for cultural & archeological replication, stop motion animation and scenery development, surgery and prostheses development and service bureaus producing consumer keepsakes, all of which rely on the combination of digital image and geometry replication using 3D scanning or photogrammetry and 3D printing to produce physical 3D human and animal forms.
3D printers certainly have resolution and colour differences that affect the final 3D printed output. But for body form applications, even the few full-colour 3D printers that are capable of producing photorealistic figurines are also, to a great degree, at the mercy of the quality of the 3D data input. To complicate matters, the 3D image capture market is changing so fast, that a choice between a 3D scanning and photogrammetry solution today, could very well be obsolete tomorrow. So how do you choose the best solution to meet your application needs?
Like any technology, the final purchase decision must heavily factor in your unique requirements. Here are some useful pros and cons of 3D scanning vs. photogrammetry for digital body form capture, as well as other useful information, to assist you in your purchase decision.
Photogrammetry vs. 3D Scanning for Body Form Applications
According to Photogrammetry.com, photogrammetry is the science of making precise measurements from photographs. The output produced from photogrammetry can be, among other things, 3D models of real subjects, including people and animals.
To digitally replicate human and animal forms using photogrammetry, multi-camera systems are precisely placed in a photogrammetry room or studio. The digital 3D image of the subject is achieved instantly using hundreds of photos taken from different angles, typically using SLR (single-lens reflex) cameras placed in the specially lit space. The geometry, or the form, of the subject is then calculated separately in software, such as AGISoft.
Photogrammetry enables instantaneous data capture, which is enormously beneficial in digital 3D body form capture. Instant data capture means that even if the subject moves ever so slightly, it does not affect the resulting 3D data capture and therefore the appearance of the subsequent 3D printed figure.
On the other hand, since a customised and complex system must be created and calibrated in a studio setting, photogrammetry can be difficult to set up and use, and is not easily portable. In addition, photogrammetry solutions aren’t able to achieve the same level of detail as 3D scanning solutions; probably hundreds of cameras would be required in a photogrammetry room to achieve comparable resolution. This limitation will affect the level of detail achieved on the final 3D printed figurine.
Unlike photogrammetry, 3D scanners process images within the system itself. This is done in collaboration with a feedback device, typically a laser in the scanner that projects a known shape onto the geometry, i.e., a laser stripe, or by using “structured light”.
The main benefit of 3D scanning is that it provides higher resolution and detail than photogrammetry. Therefore, facial details and even details on clothing are potentially captured more intricately with a 3D scanner, making the resulting 3D printed figurine more detailed and realistic as well. Scanning can be accomplished in a scanning booth, most often found in retail locations, or by using a 3D scanner in virtually any type of indoor or outdoor setting. A number of 3D laser scanners are available as portable handheld devices, offering quick and easy set up and flexibility in the location of the scan session. Structured light scanners can offer greater speed and accuracy than laser scanners when setup with large fields of view, approaching that of photogrammetry, but usually require several scanners to be synced together in order to capture the required angles without any “shadowing” due to “line of sight” and binocular vision restrictions. These multi-sensor systems, while very effective once set up, can be difficult and sensitive to calibrate.
The downside of using 3D scanners for body form applications is that they take a second or more to capture data on any part of a subject during a scan. While that might not seem like much, the living body will move ever so imperceptibly during that second. Even if the movement is only a millimeter, the result will be a double layer of scan data in the same area of the geometry, which will cause problems when creating a mesh or an STL file for the 3D printer. Labour-intensive and often complex adjustment of the scan data is required after scanning in order to prepare the file for the 3D printer. Scanning sessions themselves can take several minutes and often must be repeated in order to properly capture the complete geometry or form.
You’ll surely want to consider the massive range in cost between photogrammetry and various scanning solutions, from portable scanners that can be purchased for a few hundred dollars (USD) all the way up to scanning booths that are priced at around $150,000 USD. For example, Breuckmann and 4DDynamics structured light 3D scanners, traditionally associated with metrology applications, typically cost around $70,000 USD and require custom design and configuration. Similarly, setting up a photogrammetry studio with digital SLR cameras and AGISoft software, plus building the required systems around the software and proper calibration of the custom solution, will also run approximately $70,000 USD.
It is possible to develop a somewhat less expensive photogrammetry solution without expensive SLR cameras. You can set up 40-50 mid-priced digital cameras and place them an appropriately and constantly lit room for around $40,000-$50,000 USD.
A highly portable StructureIO scanner can be purchased for less than $1,000 USD and provides nearly comparable resolution to the $50,000 USD scanning booth. It involves some brief instruction in the relatively simple process of “painting” the subject with the 3D scanner and requires more image capture time than a booth setup. Still, the availability of affordable scanners opens up an entirely new market where a booth or a photogrammetry studio isn’t required for a body scan; you can even scan at home. Doing so means you might not need to send away for a 3D printed figurine from a service bureau costing several hundred dollars (provided you have access to a 3D printer). Using a low-cost, photorealistic colour, paper-based 3D printer from Mcor Technologies, you can print the figurine yourself for around $20 USD.
Everything’s a trade off. The less expensive photogrammetry studio solution might deliver the best value, but it won’t provide the same level of detail that you can achieve with a handheld $15,000 USD 3D scanner. That said, keep in mind that the 3D scanner will not be instantaneous or automatic and therefore will be more labour intensive in the required adjustment of the scan data. In addition, the scan session itself will take approximately 10 minutes and might need to be repeated.
Consumers have high expectations about the quality of 3D printed body form output from digital scan and photogrammetry data, yet existing photogrammetry and scan-to-print solutions can fall short of those expectations. If a 3D printed statue or bust costs hundreds of dollars, consumers rightly expect the highest-resolution, photo-quality 3D output. However, consumers might accept the quality of 3D printed output that is achievable with today’s scanning and photogrammetry technology if the solution is more affordable and they can purchase their photorealistic colour figurine for less than $50 USD, as is the case with Mcor Technologies SDL (selective deposition lamination) paper-based 3D printers. The SDL 3D printing process is the world’s only True Colour, paper-based 3D printing technology and the most affordable, safest and eco-friendly. Mcor 3D printers create detailed, durable physical 3D models from paper at 10-20% of any other 3D printing technology. Mcor 3D printed models can even be disposed of in the recycling bin for cradle-to-grave sustainability. The only 3D printing technology to include the global-standard ICC (International Colour Consortium) colour map, Mcor 3D printers produce the industry’s most accurate and photorealistic bitmap colour, making them ideal for 3D printed figurine applications.
The race is on among manufacturers of digital image and geometry capture technology to develop a solution that is affordable, off the shelf, quick and easy to set up, high resolution and fast, in order to accommodate movement. To this end, photogrammetry solution providers are trying to incorporate multi-camera systems and software into one simple, packaged solution. At the same time, makers of 3D scanners are trying to develop faster and more automatic geometry capture solutions to accommodate for movement and shorter scanning sessions. There are also major steps being taken by mainstream electronics companies and suppliers to incorporate 3D content capture into mobile phones or tablets, and this is where we are already seeing a “sea change” in the ability of average consumers to generate usable 3D content.
Currently, the choice between photogrammetry and 3D scanning for digitally replicating body forms involves compromises, and like everything else in 3D scanning and 3D printing industry, comes down to unique application requirements. Looking ahead, it is likely that we will end up with three scenarios that are, in may ways, similar to amateur and professional photography solutions available for photographing your family:
- In-home portable 3D capture and 3D printing offering low cost and low resolution, yet acceptable (and increasing) quality for the price
- Photobooth in a kiosk at retail, providing slightly better quality at a higher price than the in-home solution
- Professional studio, in a mall for example, offering additional perks, such as soft light and make up, providing the highest quality for the highest price among the three options