Digital 3D models have become a cornerstone for many industries. Traditionally, engineers used different CAD modeling tools to create a digital record of different designs, but that required time and expertise. Technologies like 3D scanning and photogrammetry have completely changed the game. Manufacturing, research, defense, and several other industries rely on 3D scanning techniques to create accurate 3D models in only a fraction of time as before.
In this article, we’ll compare the processes, capabilities, advantages, and applications of 3D scanning and photogrammetry. We’ll also go through the process of defining the approach you should take to decide between the two processes for your specific application.
3D scanning is a modeling technique that uses light to create realistic digital CAD models that can be edited, printed, analyzed, etc. The technology has numerous industrial applications due to its superior accuracy and capability of handling the most complex shapes in only a few minutes. Most modern 3D scanners can also be used without any extensive training, so you can get to work immediately.
There are a variety of 3D scanning processes, but laser 3D scans and structured light scans are the most commonly used in the industry.
3D Laser Scanning
Laser 3D scanners are extremely common in the industry. They use either a pointer or a laser line to scan all surfaces and triangulate the object. A single scan requires you to run the laser along every single surface, sometimes more than once, for an accurate reading from all sides. Laser Scanners gather several thousand data coordinates to register every single feature of the object. These data points are then transferred to the computer, which creates a mesh model for further processing.
Laser scanning is indeed considered a convenient and accurate method of generating a CAD model. However, it comes with its own share of problems. The lighting conditions have a great impact on the quality of your 3D scan. Laser 3D scanners are very sensitive to light sources and may distort the image in a well-lit room. Similarly, laser 3D scanners fail to process shiny or reflective surfaces because they can distort the light as well. To scan a shiny object, operators need to cover it in matte paint, powder, or any other textured coating.
Structured Light 3D Scanning
Structured light 3D scans use light projector and cameras instead of a laser to create digital models. The scanners project a light pattern on an object’s surface while the scanners record the deformation in the light to obtain the shape. Just like laser scanners, structured light scanners capture every view of the object. Depending on the type of scanner, the operator may rotate the object repeatedly or may move around with the scanner.
Structured light scanners generally perform better than their laser counterparts. Both blue and white light scanners are more accurate and are better equipped to handle shiny surfaces. Blue light particularly performs significantly better in well-lit areas. This makes blue light scanners suitable for on-site inspections and other outdoor applications where it’s hard to maintain optimal lighting conditions for a 3D scan.
What is Photogrammetry?
Photogrammetry is another digital modeling technique that is conceptually similar to 3D scanning. Instead of using light to gather data points, this technique uses actual photographs taken from different perspectives to deliver a digital 3D model. When compared with 3D scanning, photogrammetry has low requirements. You only need a working camera and photogrammetry software to get started. The process, however, is a little time consuming as you’ll need to take multiple photos of a single object and make sure there is a slight overlap among them.
All photogrammetry tools come with the capability of automatically aligning the photos by using the overlaps in the picture. Once the pictures are aligned, the process becomes very similar to 3D scanning. Photogrammetry software uses the triangulation method to create data points, which are then converted into a mesh model.
Common Applications of 3D Scanning and Photogrammetry
The applications of 3D scanning and photogrammetry are interchangeable. Most things you can do with 3D scanning can also be performed with photogrammetry and vice versa. However, both technologies have some limitations.
3D scanning is more leaned towards technical applications where maintaining accuracy is crucial. The process is also sensitive to the lighting conditions of the area, which makes it unsuitable for many outdoor applications in the day. Similarly, photogrammetry is preferred for applications where the textures and colors are more important. Moreover, photogrammetry works perfectly in well-lit areas, so you can use it outdoors too.
The biggest advantage of photogrammetry is its ability to replicate the colors and texture of the original object. The process is commonly used for topology inspection and area mapping where extreme accuracy is not required. Similarly, photogrammetry is also used to monitor progress in large-scale construction projects.
In the entertainment domain, realism is of paramount importance. Many games use photogrammetry to scan buildings, and other areas to keep the content as realistic as possible. The process is also commonly used by animators working with AR/VR technology. Using photogrammetry as a basic layout for further processes reduces the overall CGI required and minimizes the overall development costs of such products.
For design engineers, 3d scanning is especially useful. Designers can use an existing object as a base for their new product while engineers can carry out several important simulations and tests to ensure the performance of a part. Similarly, many product developers can use 3D scanning for their research or reverse engineering.
Another common application of 3D scanning is connected to maintenance. It is a popular method of testing the accuracy of a production setup because of its convenience and consistency. A lot of CNC machining shops, AM units, and other production environments control the quality of their output by comparing them with the available CAD file through 3D scanning.
The above use cases are only a few from the plethora of scenarios where 3D scanning optimizes your business while saving both time and overall costs. From museums digitizing their records to archeologists conducting on-site investigations, various industries are now using 3D scanning to enhance their processes today.
Interested in learning more about how 3D scanning is changing the norms of different industries. Click here!
How to Choose between 3D Scanning and Photogrammetry?
Both 3D scanning and photogrammetry can be an excellent choice for their specific applications. When deciding between the two options, you’ll need to consider the following factors.
1 – Cost
The process of 3D scanning is significantly more expensive than photogrammetry. In photogrammetry, the only thing you need is a good camera and software. Theoretically, you can even use the camera on your phone to create a digital model with photogrammetry. 3D scans, on the other hand, need significant capital investment. Suitable applications for 3D scanning usually require maximum accuracy, which means that you’ll need an excellent scanner, which further increases the required investment.
2 – Accuracy
When it comes to accuracy, 3D scanning is miles apart from photogrammetry. For engineering applications, accuracy and precision are of paramount importance. Most CAD tools do not process colors as they are not that important for reverse engineering and simulations. In photogrammetry, even small inaccuracies overlap and lead to skewed results.
3 – Speed
Processing speed is another factor that must be considered when choosing between 3D scanning and photogrammetry. 3D scanning is generally more convenient and faster as you only need to cover all surfaces through the light and see the resulting mesh model on your screen in real-time. Photogrammetry, on the other hand, requires multiple pictures, about 100 or more, from different angles. You also need to make sure that there is some overlap between the pictures, so the software can use those overlapping data points to create a realistic 3D model. All of these requirements take time, so 3D scanning becomes a better choice if you want quick results.
4 – Versatility
As stated before, photogrammetry can work even when you use your phone’s camera, provided that it is capable to take high-quality pictures. The camera doesn’t even need to be connected with a computer as you can process the files later. Contrarily, 3D scanning requires a scanner connected with the computer and has several other requirements.
5 – Functionality and applications
This is perhaps the biggest factor that determines whether you should choose 3D scanning or photogrammetry for your application. The conditions, area size, your requirements, and the applications dictate which methodology is the ideal choice for them. For instance, take the example of an engineering firm working on 3D printing a part after some modifications. The best course will be to create a digital model with a 3D scanner, modify it, and then start the printing process. Using photogrammetry in this case is not a suitable approach.
Both 3D scanning and photogrammetry are excellent technologies in their own right. However, they are only suitable for certain conditions and applications. When choosing between 3D scanning and photogrammetry, you must always consider the five aforementioned factors to make sure that you are making the correct decision.