If you want to get a 3D model made, you might be thinking whether to choose 3D scanning or photogrammetry. Each of these technologies have certain advantages and disadvantages, so how do you know which one is right for you?
It all depends on your object – it’s size, shape, texture, setting and more. Here we have listed various scenarios depending on which either 3D scanning or photogrammetry will be the best choice for your project.
First let’s see what 3D scanning and photogrammetry means and how each of them function.
What is photogrammetry?
Photogrammetry involves taking measurements of a shape and other 3D information from photographs. Multiple photographs, as many as a 100 photographs of the object are taken from different angles.
These photographs are uploading on a computer software, which tells you the exact dimensions of the object. The software uses overlapping patterns from the different photographs of the object to build its 3D model.In digital photogrammetry, photographs from a digital camera are used to reconstruct the 3D model.
What is 3D scanning?
3D scanning involves digitally capturing the shape of a physical object using infra-red light. The laser beam is pointed at the surface to be captured and the scanner converts that data into a “point cloud”. A point cloud is a set of data points in space produced by a 3D scanner.3D scanners create point clouds of data from the surface of the physical object to create its 3D model.
Now we move to which one of these technologies is right for your project. Depending upon the kind of object you want scanned – its size, shape, bulkiness, movement and more – you can see whether 3D scanning or photogrammetry will work best for you.
Still objects vs movingobjects
In photogrammetry, the person or object needs to be absolutely still. Even though slight movement can be accommodated, fast and frequent movement can ruin the results entirely. For example, if the object is an animal and an animal like a chick (living beings that do not stay still at all) it can be almost impossible to capture them using photogrammetry.
Also, in photogrammetry a studio setup with controlled environment is needed along witha multiple-camera setup for achieving the best results. The photographer needs to be expert in photogrammetry too. Even with the right setting, results can go wrong if the photographer does not capture the object correctly.
As far as 3D scanning is concerned, movement does not play havoc with the results because a small area is scanned at a time. And since you can see the results in real time, you can easily fix whatever has gone wrong.
Less texture or more
In photogrammetry and 3D scanning both, texture plays a huge role. When using photogrammetry, multiple pictures of the same object are taken from different angles.The photogrammetry software then matches features from different photographs to create a 3D image. When an object or a part of the object has very less texture and is smooth and shiny, photogrammetry does not work that wellon those areas.
There are a couple of fixes that can resolve this problem.
In some cases, you can fix this problem by making the smooth surface rough. It depends upon the kind of model you are creating. Another fix is to use an object that has a highly textured surface instead of one with a smooth, less textured surface. If you cannot alter the object or distort it, it is best to go with 3D scanning.
On the other hand, 3D scanners do better with objects with less texture. If an object is heavily textured, it makes the work of a 3D scanner difficult.An expert hand can use his or her skills to overcome this limitation.Still, if you’re looking to get the best possible results from 3D scanning, use it for objects that have a smooth, less textured surface.
Light and dark
For photogrammetry, strong lighting is needed. Low lighting, shadows and contrasts confuse the software and gives inaccurate results. That is why a studio setup with strong even lighting is used to get the best outcome.
3D scanning can even be done where there’s no daylight. 3D scannerscan work in dim lighting and also completely dark environments. However, for getting the best colours and texture, unevenly lit or dark environment are best avoided.
Small and large objects
3D scanning can be used for small, large and very large objects. Though it is much easier to scan small and medium-sized objects than enormously sized objects,that does not mean very large objects cannot be 3D scanned. A small or mid-sized object can simply be placed on a surface and scanned.When it comes to very large objects such as vehicles, aircrafts, large machines and the like, 3D scanning becomes a more complicated task though one that can be achieved.
Different kinds of 3D scanners – handheld 3D scanners, long range scanners, laser trackers etc. are used to scan very large objects. Considering that, the cost of getting a bulky object scanned rises high too.
Photogrammetry can be used for both small and large objects, but it has its limitations. Since the object is usually placed in a controlled environment with proper lighting and an extensive camera setup, capturing very large objects that cannot be moved into a room is near impossible. At the same time, if you’re not looking for a high resolution production of a very large object in its natural setting, it can surely be achieved through photogrammetry.
To sum it up, if you have a very large object and you need it in its full detailsin high resolution, 3D scanning is your best option. For small, medium and large objects, either 3D scanning or photogrammetry can work well.
3D scanning is expensive so if you will get the same results using photogrammetry (depending upon your object and its setting), use it. However, we need to remember that photogrammetry may need one or more cameras and an appropriate setting with sufficient lighting. That is one cost to consider.
Another cost to consider is this – the object, living or non-living needs to be placed in the room or a studio, so if it’s a person as the model or an animal, you will need to take into account the cost of hiring/renting and transportation. Considering all the additional expenses that will go into that, you can add up the total cost and see if it costs you less than 3D scanning.
See results in real time
When using 3D scanning, you can see the results of the scanning in real time. That is hugely beneficial to get the exact outcome you want.
Photogrammetry does not allow this luxury. You can only see the results after the entire model has been created. So if you missed out something or a part of it didn’t come out fine, you will need to go back, correct it and wait again for the entire model to process to see if it’s corrected. This essentially makes 3D scanning a faster option than photogrammetry.
3D scanner on the whole gives greater accuracy than photogrammetry. If you need to capture objects in nature or in a controlled setting, 3D scanning is your best bet. For a studio setting, photogrammetry gives highly accurate results.
If your model has very minute details, photogrammetry gives better results. Most 3D scanners can easily scan details down to 1 mm. If your object has detailssmaller than 1 mm, photogrammetry is the way to go.
Inside surfaces of an object
Since photogrammetry works by using multiple images of an object to develop its shape, it poses a problem when you have an object with surfaces on its inside that need to be captured. For example, a vehicle. 3D scanning the interiors of a truck or a car is simple with a 3D scanner, as it is very mobile and compact.It can easily be taken into smaller spaces to capture hard to reach areas. Photogrammetry, on the other hand, makes it difficult to capture the interiors of an object. It’s best used for surface capturing.
Photogrammetry is not the best choice for capturing intricate, complex patterns. For example, pipework or cave systems can be very difficult to capture using photogrammetry. Taking hundreds of photographs from different angles in places with no even or sufficient lighting is not an easy job, and a futile exercise altogether considering it will not give accurate results when loaded to a photogrammetry software.
With a single 3D scanner, you can create a 3D model on the go of lengthy and intricate patterns. Since lighting is not so much a problem, accurate results can be achieved even with difficult shapes in difficult environments.
The human hand
A brilliant model does not come by only with great equipment. Human skill is one of the most important factors in creating an outstanding 3D model. 3D scanning requires less human expertise if you’re using a good 3D scanner. For photogrammetry, the engineer needs to have deep knowledge of how the equipment works. If not, there are greater chances of things going wrong.
Where are they used
3D scanning is used in many industries, including the creative industry, manufacturing, construction, civil engineering, real estate, automotive, mining, piping, automotive, medicaland more.
Photogrammetry is popularly used for mapping and surveying, and designing. You will find photogrammetry being used in industries such as architecture, design, forestry, agriculture, artificial intelligence, military, film and television, geology and more.
We saw how a variety of factors contribute to make a success of any of these two technologies. Photogrammetry produces brilliant results, but achieving exact results depend upon a lot of factors. If those factors are favourable for photogrammetry, it can get you results that are immensely satisfying.
Also, some factors such as the texture of the object in many cases cannot be altered. In such a case, photogrammetry may not provide the results you want to see.
3D scanners are designed and calibrated for 3D scanning. Their specific function is to create 3D models from physical objects so they provide predictable results with higher accuracy.
A good quality 3D scanner is a must for achieving outstanding 3D models that have high resolution and accuracy. Taking a few 3D scans of the object to check the quality you are getting is a good way to avoid errors when you actually start scanning the model.
A low quality scan is not always the fault of the scanner. It might be due to other causes such as the density of the mesh, alignment or incorrect handling of the scanner. So take a few scans to see where you’re getting the best quality.
As technology is rapidly becoming more and more sophisticated, better 3D scanners and photogrammetry will be available in the near future, allowing us to create 3D models of almost any object irrespective of its size, environment, shape and texture. Even now, it is possible to create highly precise 3D models of almost any kind of object. You only need to use the right technology for the right object.
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