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7 things you should know about photogrammetry vs 3D scanning

7 things you should know about photogrammetry vs 3D scanning

Why pay for something when you can do it for free (or more affordably)?

Of course, nothing is entirely free. Even if you are using free photogrammetry software, you probably still need to invest in a camera to take the pictures. And the question remains: why would you pay for something if there is a solution that lets you do it for essentially free? It really depends what you want or need!

Here are the top 7 things you need to consider when trying to decide between photogrammetry and 3D scanning.

1. The all-forgiving textures

A high-resolution texture can sometimes have a very positive effect on the perception of a mesh. This is, for instance. how the cinematic industry works (very high textures with relatively low poly meshes). High resolutions work great for visual applications. If you are working on reverse engineering or plan to send your scan to a 3D printer, however, chances are you will want all the mesh resolution you can get. Take this colored mesh for instance. It looks great with texture, but it is actually pretty limited in terms of geometry.

Example of Texture before using 3d scanner

Example of Geometry using 3d scanner

2. Hold still, very still!

Another limitation for photogrammetry is that it requires the subject to be perfectly still. This is the reason why full body scanners require 20-30 cameras synchronized. Any slight movement will have devastating effect of the results:
Example of loop closure when using 3d scanner
Again, it is possible to achieve amazing results with a complete rig, but this can be a costly and bulky solution.

3D scanning, on the other hand, is a lot less affected by movement as it only relies on a smaller area at the time. A handheld device also has a significantly smaller form factor, making it much easier to carry it and bring it directly onsite.

3. What’s the deal with texture?

When working with photogrammetry, you take a lot of pictures of the same objects from different angles. The software then identifies features (found in the texture) and matches them in the different pictures. Being able to match these features between images from different angles is what makes the 3D surfaces. This works very well on an object with a lot of texture (like a rock)—but will produce very poor results on an object with little texture (like a car door).

A 3D scanner works better with objects with little texture as it relies on recognizing its projected pattern. Texture might disturb detection of the light pattern making it more difficult for the scanner to work.

4. Like working with a blindfold…

Another great advantage of using a 3D scanner is to see what you are doing in real time. This lets you see the areas you’ve scanned and, more importantly, the areas you’ve missed.

It is always possible to add more images to a photoscan, but you will need to process the whole model every time to know and see if you have everything you need. Processing large scans with a lot of pictures can take a long time. This also makes the use of 3D scanning as process significantly faster than using photogrammetry.

5. What kind of accuracy can you expect?

It is possible to obtain great looking scans with photogrammetry—but getting good accuracy is more challenging and more random as a lot of parameters are simply not controlled. Cameras (even the good ones) are generally not optically calibrated for the purpose of 3D scanning. This can create important scaling errors in a 3D scan.

3D scanners (the good ones at least) will generally be calibrated for the purpose of scanning. They provide more of a controlled ecosystem making them more predictable hence the possibility to provide accuracy specifications.

6. The difference between interior and exterior…

Again, photogrammetry works great if you can get all around the subject and take a good number of pictures, but what if you are trying to scan the interior of something in more of a confined area? Think of trying to scan the inside of a car for instance. Getting the right number of pictures of all components from all angles will be nearly impossible making it practically unfeasible to scan the inside of object with this technology.

This is where having a 3D scanner with a small form factor will definitely be handy. As you can easily get it into, around or under things, scanning objects from all angles will be a lot more achievable.

7. How much time can you invest in onboarding and training?

This is something you hear a lot: “Oh, the things he can do with his equipment!” Many people have the preconceived notion of being competent or qualified with a device or system. This is a system that relies on its user to deliver great performance. When you know how to use it, it works pretty well. However, getting there can sometimes be painful. And if the system is to be used by more than one person, these new users also have to learn how all of its ins and outs.


A system that does not require any training or specific scanning knowledge is, therefore, a great bet. This is the case with good 3D scanners as they will prevent users from collecting bad-quality data and deliver great performances regardless of the way they are used.


Overall, when choosing between photogrammetry and 3D scanning, you really have to consider your needs and applications. In some cases, and for some applications, photogrammetry is definitely interesting but, just like about anything, it is not suited for everything.

 

3D scanning of biblical proportions!

3D scanning of biblical proportions!

The Centre de conservation du Québec is the leading conservation centre in the province of Québec—and a real gold mine for hidden treasures and artefacts. I was actually looking for a location to take pictures with the peel 3D affordable scanner when I visited centre and came across a particularly interesting 3D scanning project.

A large-scale statue of Alphonsus Liguori immediately caught my eye. Saint-Alphonse-de-Liguori was a Catholic bishop, founder of the Redemptorists, the community that administered St. Patrick's parish in Québec City from 1874. Dressed in the attributes of a bishop and holding a stick, the statue makes a gesture as if he is blessing someone. It was made of a wooden core covered with metal sheets (copper, steel and…lead!). This manufacturing technique was very common in Québec in the late 19th century.

original size statue

Despite the best efforts to preserve statues like this one, wear and tear inevitably reared their ugly heads. Why? The statues were originally installed outside and exposed to weather (did I say weather can be harsh in Canada?). Water from the rain, snow and even condensation eventually found its way and significantly deteriorated the wooded structure.

Classical restoration of a similar piece would normally involve hundreds of hours of labor and removal of the metal wrapping, an operation especially delicate to avoid all possibilities of lead contamination. Such a restoration is, unfortunately, a very costly endeavour for parishes, which generally have limited budgets.

This is where peel 3d, an affordable 3D scanner with professional-grade features comes into play with a brand-new approach to 3D scanning. Instead of restoring the original piece, the plan would be to create a geometrically-exact replica. We started by 3D scanning the statue using peel 3D. The entire process only took minutes and, once cleaned and finalized with peel 3D’s scanning software, we generated an accurate model that was ready for CNC machining.

peel 3d managed to catch the finest details, the only issue was that the statue had been scanned in its deteriorated state and flaws and defects were also observable in the scan as well…

details of a statue 3d scan with peel 3d scanner

This is where virtual restoration came into play! We exported the data towards Sculptris and virtually corrected the different flaws until we obtained a model as perfect as the original. Data is corrected very similarly as you would using a clay model—but with full control and no limitations (for one thing, I’ve never seen a clay model with an undo button 😊).

The result is a stunning, high-quality, high-resolution, and accurate replica model that is ready for machining.

statue 3d scan results with peel 3d scanner software

Here is the final result.

All peel 3d sample files (including this one) are available on our Sketchfab page.

The plan is to revive this treasure by bringing it to the 21st century and building an exact replica using modern materials, better adapted to the environment. Using accessible material and modern technology will also make it significantly cheaper to manufacture a brand-new statue than restoring the original model. Using the peel 3D affordable scanner, we also separately scanned and virtually restored the staff.

Another very positive aspect of having a virtual model is that we are able to scale it. If required, the parish could 3D print a smaller version of the statue.

There are dozens of similar statues in similar conditions in Quebec and around the world that could benefit from a similar treatment. Parishes and other conservation centres can showcase very accurate replicas of their religious heritage by using the professional-grade peel 3D scanning technology while preserving the original works in a proper conservation environment and keeping their costs in check.

Taking peel 3d to higher grounds … literally!

Taking peel 3d to higher grounds … literally!

It was a bright sunny day when I arrived on site to give Rino Côté a hand with his artistic project. We’ll scan parts of a tree in a nearby public park, he said. It was an old ash tree that had been devastated by the emerald ash borer, a tragedy really! Rino’s plan was to turn whatever was left of this once-majestic tree into a work of art. POP! He called it. The idea was to attach bright-red bubbly foam to certain areas of the tree as if whatever life left in it was slowly fizzing out, ironically making this dead tree look more alive…

Rino’s original concept for POP!preparing a 3d scan of a tree

His plan was to scan certain areas of the tree and use the 3D data to design custom made 3D printed parts that would later get attached directly to the wood. The project was challenging enough and not too far away; I just had to say yes!

The tree had been stripped of its bark and branches, it looked like a telephone pole really, but it was only when standing in front of it that I realized the height of the thing; it was huge! A few hours into the project we were 25 feet in the air, standing on 8 inches-wide planks at the top of a scaffolding. It was then that I realized that I didn’t so well with heights. Don’t look down, don’t look down… Luckily the scanner was working great! We were able to bring it up with us and scan the different areas needed for the project.

There wasn’t a cloud in the sky, it was a hot day. Besides staying well hydrated, we had to provide the scanner with a bit of shade for it to work right. We did using opaque fabric scraps. It was the worst possible light conditions, but it worked hence answering the question: “Can you use peel 3d outside?” We had access to a simple extension cord to power the laptop and scanner; a generator or battery would have worked as well. We made it safe and sound.

The different parts were designed using TINKERCAD (for the bubble shapes) and Geomagic (for Boolean operations), and printed in red PLA All the parts were also prepared and coated with a special varnish UV block  for the sometimes harsh weather in Canada before being attached.

Final parts before being installed:

bubbles produced after de 3d scan

Needless to say, the parts fitted perfectly, the masterpiece is now complete and “exposed” to the Jacques-Ferron cultural center in Longueuil. Here is the final look:

Complex fit of an installed custom-made part. second view of a tree project after a 3d scanning