You must have heard somewhere people say 3D photography and 3D scanning, right? And somewhere, you also have the thought "Ah, 3D shooting, 3D scanning, they are all 3D images, so they must be the same."
So, are 3D Imaging and 3D Scanning the same thing as many people think?
We will find the answer together in this article.
1. Scan 3D
1.1 Definition
There are two most common types of 3D scanning - laser and structured light 3D scanning.
Laser scanning uses a laser to measure an object's geometry and create a model through the resulting data. The laser beam is scanned over the surface and the device uses the beam projector's angle encoder and the returned "time of flight" to calculate the position of each point in 3D space. After all points are captured and recorded, a dense point cloud will appear. To capture a complete object, the laser scanner or the object is moved and the scan repeats. Optionally, additional software can connect points to create polygon meshes for 3D modeling and design purposes.
(Nguồn: 3D3 Solutions.com)
Structured light 3D scanning using a projector (usually an LCD monitor) and at least 2 cameras to map an area or object. Light patterns are projected onto a surface, and the camera then records the surface by measuring where and how the light deforms around it. To ensure every angle is captured, the scanner is moved around the subject or the subject is moved in front of the scanner. The result is a point cloud similar to what a 3D laser scan produces, with the same option of creating a polygon mesh.
1.2 Pros and cons of 3D scanning
1.2.1 Pros
- High precision and high resolution.
- This method works well for small parts and can generate data points in real time. This saves time, as you will see which areas need to be rescanned or have been missed before entering the design phase.
1.2.2 Cons
- Light interference can create unfavorable 3D scans. Both laser and white light scanners read light sources to collect data. If there is too much ambient light, the collected data may be distorted. Similarly, 3D scanners also have trouble with shiny or reflective surfaces. These surfaces tend to pass light away from the input sensors making scanning more difficult. This problem can be fixed, but it will probably change the original shape and texture of the object.
- One of the biggest downsides of 3D scanners is the price. Machines can be worth tens of thousands of dollars. As technology advances, you will need to buy new scanners to keep up with the technology.
- Another downside is the size and portability of the device.
2. 3D imaging (or photometry)
2.1 Definition
Photometry is another method used to create 3D models. Instead of using active light sources, this technology uses photographs to collect data. Photo measurement requires only a camera, a computer and specialized software.
To create a 3D model using photometry, photos are taken from various angles to capture every part of the subject with overlap from one image to another. This overlap is necessary for the software to align the photos properly. After all images are captured, they are imported into photogrammetry software, which aligns the images, plots data points, and calculates the distance and position of each point in 3D space. . The result is a 3D point cloud that can create a polygon mesh, much like a 3D scan.
2.2 Pros and cons
2.2.1 Pros
- Price and accessibility. Cameras and imaging software are often less expensive and easier to transport. You may also already have a camera (mobile phone's camera).
- The ability to reproduce an object in full color and texture. Although some 3D scanners are also able to produce this, photometry produces photographs that accurately depict reality.
2.2.2 Cons
- Photometrics has its drawbacks. When using the scan method, as described above, textures play an important role in how the reference points are created, working with smooth, flat or uniform surfaces can be difficult. There are a number of ways to combat this, but they can be cumbersome or unavailable. Photometric projects also sometimes require more processing time in the office.
- Because the subject has to be photographed at many different angles, even having to move the object or camera many times, it will be time consuming and risky for the device and the object.
3. So which one should you choose?
- 3D laser scanning and photometric measurements great in their own right. When deciding which is best for your needs, you need to consider your budget, the size of your area, and the level of precision you need.
- 3D scanning is suitable for capturing dense clouds of surfaces with little texture. 3D scanning is useful for capturing areas of great detail and requires high precision.
- When you need to render a landscape as a 3D model for an archaeological survey or for film graphics, photogrammetry is the way to go. Since capturing the realism of the scene is paramount, optical measurement will yield better overall results than 3D scanning while also being more cost-effective.
Source: www.photomodeler.com
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