3D Scanning as a Complement to 3D Printing

2/16/2014

For all of the press (and let’s face it, hype) that 3D printing has received, I’m surprised that more attention hasn’t been paid to a mutually supporting technology – 3D scanning. Just like 3D printing, 3D scanning has undergone a burst of development in the last few years that has brought the associated costs out of the stratosphere and within reach of small firms and consumers. There are basically two different scales of 3D scanning: large scale, building-size scanning and smaller scale hand-held type scanning. Fortunately, I’ve been lucky enough to have had experience with both.

Large Scale 3D Scanning

Large scale scanning became accessible to smaller AEC firms with the introduction of the Faro Focus scanner in 2011. Prior to that, 3D scanners would run to six figures in cost for even the most basic models. The Faro Focus brought that down to around $30K – by no means a consumer-level price, but certainly within reach of a moderately-sized AEC firm.

I was fortunate enough to work for a such a firm, and got to use a Faro Focus scanner quite a bit. I was amazed by how it performed. The scanner itself was about the size of a lunchbox, and sat on top of a tripod. There are number of different types of technology that are used in different 3D scanners, but the principle is similar between all of them. In the case of the Focus, it projected a multitude of laser beams that would record the X, Y, and Z coordinates of everywhere the beams struck. It is quite similar to a laser measuring device, which uses a laser beam to determine the distance of a distant object. The 3D scanner basically does the same thing, just much more rapidly – up to nearly 1,000,000 points a second. Color information can be added with the use of the built-in digital camera, which can assign an RGB value to each of the location values. The Focus could measure a nearly spherical view of its environment (less a conical dead spot beneath the scanner where the tripod is located), up to a range of 330 meters.

The result is a huge file called a “point cloud” that contains all of the X, Y, Z and RGB values. Manipulation of such files can use up a lot of computing resources – some point clouds contain billions of data points. What’s more, there are very often multiple point cloud files that need to be processed. Since the scanner works on a line-of-sight basis, multiple scans must be taken in order to get a complete picture of the space being scanned. For large or complex spaces, this can require many such point cloud files. For example, a complete scan of the interior of the University of Oregon student union required several hundred scans to complete.

Once the scanning has been completed, then these multiple files need to be combined, though a process called “registration.” This can get tricky, and is usually more time-consuming than the actual scanning process. In general, it takes about eight hours of registration for every hour of scanning. Complicating matters is the fact that the different types of registration software vary greatly in their capabilities. Planning before the scanning is paramount to getting the scans to register or fit together properly. Planning the placement of the scanner to get the best results for the fewest scans can be tricky. Also, the placement of targets (usually either spheres or paper checkerboards) can make or break the ability to correctly register the scans. In general, the more targets you can put up, the better.

With proper planning and perseverance, you will wind up with a highly accurate series of registered scans that will accurately portray the physical characteristics of a building to within a millimeter or two. The scans can then be modeled in a BIM application such as Revit to provide an accurate model of a space. Anyone who has worked on the renovation of a building that is large or old (or both) knows that the “as-built” drawings are anything but that. Minor renovations – or even large ones – are frequently not documented with any degree of accuracy, or even at all. This can often lead to unpleasant surprises during design or during construction, resulting in costly delays or change orders. The traditional way design firms have of documenting existing conditions – sending a couple of interns to the building with a tape measure and a clipboard – is also time-consuming and scope-limited. While the initial investment in a large scale scanner may seem steep, for any firm that engages in renovations and retrofits, the return on investment comes pretty quickly.

Following is a 3D scan of Tesseract Design’s HQ. The scan was mostly of the interior spaces, which appear as rectangular volumes in the lower right of the image. The partial facade is the result of a single scan taken outside the front door.

Image of interior and partial exterior scan of building housing Tesseract Design.

Image of interior and partial exterior scan of building housing Tesseract Design.

Small Scale 3D Scanning

Hand-held 3D scanners have also been around for awhile, but only last fall were models introduced that priced them within reach of the consumer/hobbyist market. First out of the gate was MakerBot, which introduced the Digitizer in October 2013. It’s initial price of $1400 was a bit steep, but still much more affordable than many other small-scale scanners. In fact, the Digitizer is not a hand-held scanner, but a stationary scanner which used a turntable to rotate objects in front of a camera/laser assembly. This severely limits the size and weight of objects which can can scanned (to 8 inches and 6.6 pounds, respectively).

As much as I like MakerBot’s 3D printers, I wasn’t interested in ponying up this kind of money for a scanner that had such limitations on the scale of the objects which can be scanned. I decided to wait, but fortunately I didn’t have to wait long. Less than a month later, 3DSystems rolled out its hand-held Sense scanner at a price of $399. I jumped on that one pretty quickly, and Tesseract Design had a Sense scanner in the office before Christmas.

Besides the sizable price differential, there are some basic differences between the Digitizer and the Sense. While the Digitizer has serious limitations on the scale of the objects it can scan, the Sense can be used to scan objects up to 10 feet on a side. However, it does a pretty poor job of scanning small objects. A jewelry-maker friend of mine asked me to scan an antique lamp base that was about 5 inches across – the scan came out looking like a partially-dissolved sand dollar. Larger objects tend to work out better, and I’ve had enormous success scanning my family and friends. The proprietary software that the Sense uses is a mixed blessing. It does a fantastic job of keeping track of the object being scanned – usually. Sometimes it will lose track of the scan target and there is no recourse but to start over. Also, you need to keep an eye on your computer screen while doing the scanning, which resulted in my doing some amusing calisthenics to keep my eyes on the desktop screen while circling the subject of the scan. My biggest gripe with the software is that there is no way to store the scan point cloud in its native format. Consequently, all of the high-level post-processing functions such as cropping, smoothing, etc. must be done as soon as the scan is completed, and then exported to an STL or OBJ file format.

3D Modeling, Scanning and Printing

One of the most promising things about the increased availability of 3D scanning technology is its application to 3D printing. Much commentary has been launched about the need for a “killer app” for 3D printing. The problem thus far has been: I’ve got a 3D printer, now what do I print? Online libraries such as Thingiverse have an ever-increasing inventory of cool stuff to print. However, the user is still limited to what is available in the libraries.

Using 3D modeling tools is the obvious solution to this problem. If you have an idea for a neat thing to print, you simply model it up in a 3D modeling program, export it as an STL or similar file, and start printing. There’s a problem with this concept, though: it’s difficult to “simply” model something in a 3D modeling program. Most 3D modeling software has a pretty steep learning curve. I’ve been using Revit for a long time, and have been able to create and print 3D objects that I’ve modeled in Revit. It hasn’t been easy, though – and my conclusion is that Revit is a great tool for creating 3D models of buildings (and much more), but it doesn’t really lend itself to creating models for 3D printing. It can be done, but it requires a lot of tweaking and processing to get the Revit model to the point where it is going to be able to be printed with a 3D printer. Other tools seem to be much more suitable to this task. I’ve been trying to get more proficient with another application called 3D Studio Max. This is an amazing tool, and in the hands of a skilled user can generate really fantastic 3D models, renderings and animations. I have just been able to scratch the surface of 3D Studio Max and generate and still print some really neat things. However, I know that there is much more that I can do with this tool, if only I can gain a little more knowledge and experience with it. It’s very powerful, but also highly complex to use and tricky to learn. Other, simpler (and cheaper) tools are available as well, such as SketchUp, Blender and 123D. To be honest, I haven’t put a lot of time into learning how to use these tools (I’m still trying to get more out of 3D Studio Max). My overall impression is that there is a tradeoff between the ease of use of these 3D modeling applications and the complexity of the objects that can be modeled with them. I also know that there are other folks who are trying to flatten the learning curve on 3D modeling so that it can be accessible to the casual user that doesn’t have the time or technical interest in learning how to use a powerful 3D modeling tool. This could be the “killer app” that the 3D printing world is looking for.

In the meantime, 3D scanning is now within reach of the consumer-lever 3D printer. I’ve had pretty good results using the Sense scanner to scan and print moderately-sized objects. My family and friends have been very patient and supportive when I scan and print them, and so far the results have been pretty impressive.

Print of 3D scan of noted Portland curmudgeon O. Canobite

Print of 3D scan of noted Portland curmudgeon O. Canobite

All in all, I think that 3D scanning has been overlooked in the media attention that has been given to 3D printing. Just like 3D printing, the cost of the technology has in the past few years dropped to the point where it is much more easily accessible to the consumer or small business. Architectural-scale 3D scanning strongly complements the already powerful tool set that can be found in BIM technology. Smaller-scale scanning complements the promise inherent in desktop 3D printing, and can help bridge the “killer app” gap in content creation for 3D printers. I’m definitely going to keep my eye on how this technology evolves alongside BIM and 3D printing. I think there are great things on the horizon for all three.

For more information on Tesseract Design’s 3D scanning services, please see www.tesseract-design.com/additional-services