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:
- AliceVision Meshroom (converts the photos into a 3D file)
- Meshlab (3D scan cleanup and alignment of the individual 3D scans)
- Netfabb free version 7.4.0 (measurement of the 3D scan)
- GOM Inspect (examination of the scan)
Step 1: Manual measurement of the object
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
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
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.
After Meshroom has computed the 3D model from the pictures, you will find the OBJ file in the cache folder, in the subfolder “Meshing”.
Step 4: Cleanup of the 3D scan 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.
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.
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.
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.
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.
With the “Select Faces in a Rectangular Region” function we remove overlapping surfaces and double geometry.
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.
The free 3D scan has an average deviation of just 0.2 mm from the professional 3D scan. An amazing result.
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:
- Demo part 3D scanned with cell phone camera (STL file)
- Demo part 3D scanned with professional 3D scanner Artec “Space Spider” (STL file)
- Nominal/actual comparison between free 3D scan and professional 3D scan (PDF)
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.