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How to 3D scan for free?

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3D Scanning for Free 09:33
You only need a mobile phone and some free software to create a free 3D scan. The technique is called photogrammetry. We 3D-scanned the same part twice—once for free and once with a professional 3D scanner—then compared both 3D scans. The result: The free 3D scan has a deviation of only about 0.2mm compared to the professional 3D scan.
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Holocreators is a 3D scanning company. We offer you a professional 3D scan service with an
accuracy of up to 0.005mm. We’d love to help you with your project. Call us at +49 40
481133
or write us an email: info@holocreators.com

Comparison between a photogrammetry 3D scan and a professional structured-light 3D scan
Swann Rack / Holocreators Left – Free scan / Right – Professional scan

With this tutorial, we show you all the steps to create a free 3D scan. As an example, we 3D
scan a metal part from the fuel tank of a car. The part is called “Tankgeber” (fuel sensor):

To follow this tutorial, you need these free software packages:

Step 1: Manual Measurement

Measuring a metal part with a caliper
Swann Rack / Holocreators Measuring a metal part with a caliper

First, we measure our part (“fuel sensor”) manually. To minimize errors, we measure three
times with the caliper and determine the average value. This way, measurement outliers are
eliminated. We determine an average diameter of 76.2mm. This is the reference dimension,
which will be very important later on.

Photogrammetry (that’s the name of this 3D scanning technique) has the disadvantage that
it can’t produce correct measurements. Therefore, we need a reference measurement.

The reason is that the 3D model is calculated from photos, and the computer does not know
how big the part actually is.

Step 2: Taking Pictures of the Part

Taking a picture of a metal part using a cell phone for photogrammetry
Swann Rack / Holocreators We take (at least 100) pictures of the part with a mobile phone camera from different angles
and perspectives

We place the part on a box and take lots of pictures from different angles and perspectives
with a cell phone—the more images, the better. Take at least 100 photos.
Good lighting is important. Photogrammetry works best with diffuse lighting. Fluorescent
tubes work great. Shadows have a negative effect on the photogrammetry process. The
object we want to 3D scan should have distinctive geometric features and should not be
reflective. Use spray chalk, if it’s too reflective. Take two photosets—one with the part
upright and one inverted to capture the interior features

Step 3: Creating the 3D Model (photogrammetry) in Meshroom

Imported photos in the photogrammetry software Meshroom
Swann Rack / Holocreators We import the photos to Meshroom

Next, import all the photos into the Meshroom software— simply by drag-n-drop. Press start
and the software does the rest. After the software has calculated the 3D model, the data is
exported as an OBJ file. (OBJ is a very similar format to STL and can be processed in the same
way.)

Saving a window for the cache folder in Meshroom
Swann Rack / Holocreators After we click the “Start” button, Meshroom asks where to save the MeshroomCashe folder

Many users have the problem that they cannot find the 3D model (OBJ format) created by
Meshroom.
When we click the “Start” button in Meshroom, we are asked where the cache folder should
be created. The project files are then stored in this folder. The “MeshroomCashe” folder
contains the subfolder “Meshing,” where the 3D scan is saved as an OBJ 3D model.

Folder where the 3D model in obj format is saved in Meshroom
Swann Rack / Holocreators In the subfolder “Meshing” the 3D model is stored in OBJ format

Step 4: 3D Scan Cleanup in Meshlab

Select faces in rectangular region button in Meshlab
Swann Rack / Holocreators Select “Select Faces in a Rectangular Region” in Meshlab

Import the 3D scan (OBJ format) into Meshlab. Remove all unneeded geometry not wanted
in the 3D Scan. For this, use the function “Select Faces in a Rectangular Region”. Select
unwanted areas in red and then press the “delete”.

Selecting faces on the 3D scan in Meshlab
Swann Rack / Holocreators Cut away unneeded geometry

Once the 3D scan cleanup is complete, i.e. removed all unwanted geometry, we export the
3D model in STL format. Repeat this process also for the inside 3D scan.

Step 5: Measuring and Resizing in Netfabb

In Netfabb, measure the 3D scans and adjust the size using the reference diameter
determined earlier by manually measuring the part. To do this, import the STL file into
Netfabb and click on the “new measuring” button.

New measuring button in Netfabb closeup
Swann Rack / Holocreators In Netfabb, click on the “New measuring” button
Radius of the 3D scan in Netfabb
Swann Rack / Holocreators With Netfabb, measure the outer radius of the flange from the 3D scan

Determine the outer radius of the flange. It has a diameter of 6.98mm in the 3D scan.
Initially, manual measurement produced a value of 76.2mm. Therefore, we divide
76.2mm/6.98mm and get a scaling factor of 10.91. With this factor, we rescale the 3D model
to get the part’s original size.

Rescaling in Netfabb
Swann Rack / Holocreators Enter the new scaling factor (10.917) into Netfabb

Step 6: Realignment of Both 3D Scan Halves in Meshlab

Import both rescaled 3D scan halves back into Meshlab to line up and connect them
correctly. This process is called “alignment.”

Imported top and bottom 3D scan in Meshlab
Swann Rack / Holocreators Import both 3D scans into Meshlab
Alignment button in Meshlab
Swann Rack / Holocreators Click on the yellow “Align” icon
Glue mesh here button in Meshlab
Swann Rack / Holocreators Select the upper 3D scan and click on “Glue Mesh here”
Aligning two different 3D scans in Meshlab by matching and marking similiar points
Swann Rack / Holocreators Select matching points on both 3D scans

To help the software fit the 3D models correctly, select at least three matching points on
both 3D scans. Then click on “Process,” and the software aligns both 3D scans.

Removal of overlapping geometry from the 3D scan in Meshlab
Swann Rack / Holocreators Using the function “Select Faces in a Rectangular Region” remove overlapping geometry

Both 3D scans still have overlapping areas. Use the function “Select Faces in a Rectangular
Region” to remove this duplicated geometry.
Finally, right-click on the upper 3D scan in the right list and select “Flatten Visible layers”.
This function merges both 3D Scan halves.

Now the 3D scan of our part (“tankgeber”) is completed.

Step 7: Checking the Accuracy of the 3D Scan in GOM Inspect

We want to check how accurate our free 3D scan is. Therefore, we have 3D scanned the
same part with the professional 3D scanner Artec Space Spider. In the software GOM
Inspect, we compare both 3D scans and check the accuracy of the free 3D scan. With this
data, we created a deviation analysis.

Result: Our free 3D scan is pretty accurate. On average, it deviates only 0.2mm from the
professional 3D Scan.

Deviation analysis between the photogrammetry 3D scan and the professional structured-light 3D scan
Swann Rack / Holocreators With a deviation analysis, we determine the 3D scan accuracy in GOM Inspect

Download of the Project Data

We have provided both the free 3D scan and the professional 3D scan for you to download.
The deviation analysis, which compares both 3D scans, is also available for download:

Conclusion

It is very impressive that we achieved this 3D scan result with only a mobile phone camera
and free software. Accuracy of 0.2mm was previously reserved for professional 3D scanners.
Nevertheless, the professional 3D scanners have their merits. They are calibrated and
guarantee a level of accuracy, which is very important when measuring critical parts. Also,
the 3D scan is much faster with a professional 3D Scanner. The free 3D scan required about
3 hours, while the professional 3D scan was completed 15 minutes.

Do you need help with a 3D Scan?

Holocreators offers professional 3D-scanning and reverse engineering services. If your
project requires the use of professional 3D scanners and a guaranteed accuracy from 0.1mm
to 0.005mm, then please feel free to call us at +49 40 481133 or write us an email:
info@holocreators.com

Swann has been enthusiastic about everything 3D for many years. His roots lie in analog holography, which brought him to digital 3D-modeling in 2011.

The rapid progress of various 3D-scanning techniques fascinated himso much thathe founded Holocreators together with his brother Miro Rack in 2015.

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