Home 3D Scanner Tutorial: 3D Scanning for Free

Tutorial: 3D Scanning for Free

How to create a 3D scan for free? All you need is free software and your cell phone camera. For this tutorial we 3D scanned the same object once with free software and a cell phone camera and once with a professional 3D scanner. The result was surprising: The free 3D scan differs on average just 0.2 mm from the professional scan.

For our tutorial we used this free software:

Video-Tutorial

Step 1: Manual measurement of the object

Measuring the part with a caliper
Measuring the part with a caliper

Photogrammetry has the disadvantage that it doesn’t record correct measurements. That’s because the software calculates the 3D model from photos. We need to measure the part to determine a reference diameter. This will allow us to rescale the 3D scan later in the software. To minimize errors and avoid outliers, we measure at least three different locations and determine the average diameter of the part: 76.2 mm.

Step 2: Creation of photosets

Photographing the part with a cell phone camera
Photographing the part with a cell phone camera

We put the part on a box and photograph it with a cell phone camera. We move in a circle around the object and take at least 100 pictures from different perspectives. Good lighting is crucial for a good 3D scan. The light should be as diffuse as possible. There shouldn’t be any shadows cast on the part. Fluorescent tubes are very suitable for lighting. The object shouldn’t be too reflective. A chalk spray from the hardware store can reduce reflectiveness. We want to create two 3D scans, so we make two sets of photos: For the first 3D Scan the part sits on the flange. For the second 3D scan the parts is upside down so we can capture the inside.

Step 3: Creation of the 3D model (photogrammetry) in Meshroom

Meshroom Photogrammetry Software
Meshroom Photogrammetry Software

In the next step we import all photos into the software “Meshroom”. This is done by by drag and drop. After all images have been imported, the software automatically computes the 3D model. All you need to do is click on the “Start” button. The finished 3D model can be exported as an STL file. Some users have had the problem that they couldn’t find the 3D model created by Meshroom.

When you click the "Start" button for the first time, Meshroom asks where the cache folder should be saved.
When you click the “Start” button for the first time, Meshroom asks where the cache folder should be saved.

After Meshroom has computed the 3D model from the pictures, you will find the OBJ file in the cache folder, in the subfolder “Meshing”.

The 3D model is saved as OBJ in the subfolder "Meshing"
The 3D model is saved as OBJ in the subfolder “Meshing”

Step 4: Cleanup of the 3D scan in Meshlab

 Press the "Select Faces in a Rectangular Region" button in Meshlab
Press the “Select Faces in a Rectangular Region” button in Meshlab

Inside Meshlab we do the 3D cleanup. All unnecessary geometry will be removed. We do this by clicking on “Select Faces in a Rectangular Region”. Unwanted geometry can be highlighted in red and removed by pressing the delete key on your keyboard.

Highlight unwanted geometry in Meshlab
Highlight unwanted geometry in Meshlab

The process is done for both 3D Scans. Once the redundant geometry is completely removed, the 3D scans can be exported as an STL file.

Step 4: Measuring and scaling in Netfabb

To measure and rescale the 3D scans, we import them into Netfabb. Here we and click on the button “Measure” and outside diameter of the flange.

Measuring the 3D scan in Netfabb
Measuring the 3D scan in Netfabb
Determining the outer radius in Netfabb
Determining the outer radius in Netfabb

The outer radius of the flange was measured at 6.98 mm. However, our manual measurement had shown a diameter of 76.2 mm. To get the correct scaling, we now divide 76.2 mm by 6.98 mm, resulting in a scaling factor of 10.91. With this factor, we can now rescale the 3D scan to get the true dimensions of the part.

Insert the scale factor in Netfabb
Insert the scale factor in Netfabb

Step 5: Alignment of the 3D scans in Meshlab

The two rescaled 3D scans can now be imported back into Meshlab to realign and merge them.

 Import of 3D scans into Meshlab

Import of 3D scans into Meshlab
Click on the button "Align"
Click on the button “Align”
Select the top 3D scan and click on "Glue Here Mesh"
Select the top 3D scan and click on “Glue Here Mesh”
Select the bottom 3D scan and click on "Point Based Glueing"
Select the bottom 3D scan and click on “Point Based Glueing”

For Meshlab to be able to correctly align the two 3D scans, at least three matching points must be manually selected on both scans. By clicking on “Process”, the software aligns the two 3D scans.

Select the matching geometry in both 3D scans
Select the matching geometry in both 3D scans

With the “Select Faces in a Rectangular Region” function we remove overlapping surfaces and double geometry.

Remove overlapping geometry using the “Select Faces in a Rectangular Region” feature
Remove overlapping geometry using the “Select Faces in a Rectangular Region” feature

Once we are happy with the result we can merge both 3D scans. We select the upper 3D scan and make a right click to “Flatten Visible Layers”. The 3D Scan is now complete and can be exported as an STL file.

Step 6: Comparison of the Free 3D Scan and the professional 3D Scan in GOM-Inspect

In a final step we want to check the accuracy of the free 3D scan. To do this we scanned the same part with the professional 3D scanner “Space Spider” by Artec. The GOM-Inspect software allows us to determine deviations between the two 3D scans. This process is called nominal/actual comparison.

Nominal/actual comparison of the free 3D scan and the professional 3D scan in GOM Inspect
Nominal/actual comparison of the free 3D scan and the professional 3D scan in GOM Inspect

The free 3D scan has an average deviation of just 0.2 mm from the professional 3D scan. An amazing result.

Download

We provide you with the download links to both the free 3D scan and the professional 3D scan. You may also download the nominal/actual comparison here:

Conclusion

We were very surprised by the accuracy of the free 3D scan. The deviation between the free 3D scan and the professional 3D scan was just 0.2 mm, which is an excellent result. Nevertheless, professional scanners certainly have their justification: The free 3D scan with photogrammetry took us three hours and is therefore very time-consuming. In contrast, the professional 3D scan with the Artec “Space Spider” took us only 15 minutes. In addition, professional equipment is calibrated and guarantees an accurate result – especially when measuring critical components.

If you have a project that requires the use of professional 3D scanners and a guaranteed accuracy from 0.1 mm to 0.005 mm, please call us at +49 40 48 11 33 or write an email: info@holocreators.com)

Holocreators GmbH offers you a 3D Scan Service and 3D Data Processing Service. We can 3D scan objects with an accuracy of 0.1 mm to 0.005 mm. We are happy to help! Call us: +49 40 48 11 33 or write an email: info@holocreators.com.