Recently AccuPixel won another tender – this time to scan cultural heritage objects for a museum. The pandemic has forced us all to think differently and education is no different, so if the museum cannot open why not let a virtual visit happen online?
We have around 25 objects to scan, ranging from fossils to glove stretchers and a second world war steel helmet. All are small enough to fit inside our light box and turntable.
Just in Time – Metashape 1.7
With the publication of Metashape 1.7 we get a new tick box on the Align menu: Exclude stationary tie points.
Static tie points are what we seek and photogrammetry founded on the principles of everything remaining motionless in the scene. How can we ignore static points yet still get a 3D reconstruction?
This tick box tells Metashape to take a longer look at the tie points and to figure out what the subject really is – even if its moving in the scene – and ignore any point that is in the scene and is unchanging. It’s as if we have a means to set the context of what is really important in the images.
Exclude vs Include
We took the first set of images and ran it with Exclude stationary tie points checked. The first pass results delivered exactly what we needed with all images aligned in their predicted position around the subject:
150 cameras all aligned in a circular arrays, even coping with the fact the object was turned over during the capture process.
Next, and just to prove it really did work, we ticked off the Exclude stationary tie points box and re-ran alignment:
The results were unusable. 115 of thee 150 images aligned but they were all stacked on top of each other in two groups. The stationary tie points had been interpreted correctly and the moving object was ignored.
Conclusions
The job of scanning the museum artefacts suddenly got a lot easier and quicker! We always strive for efficient working and this tick box goes a long way to support this ethos. We don’t know how this works when handheld and the test is restricted to tripod mount and remote release. If we get time we will test handheld but for now the priority is completing the job.
In the very near future we will add another topic to the Metashape Standard Edition online course – this technique and method is worth sharing in far more detail.