ScanTheWorld - Lion Sculpture in Halle (Saale)

This is probably one of the most famous sculptures in my town, and thus it needed to be scanned ;) I will try to collect as many digital souvenirs of various places, and maybe some of you want to join.

This is only one of a pair of lions that is situated in front of the central building of the Martin Luther University of Halle-Wittenberg, which is known to locals as the Löwengebäude ('Lions Building'). They were created in 1822 for the Silesian town of Bunzlau (now Bolesławiec) and moved to Halle (Saale) in 1868.

See and download the 3d model on Sketchfab


Scanning cast iron surfaces is usually quite a challenge, but I am happy, that the OpenScanCloud engine (see Github) did a wonderful job with those 129 photos (Iphone XS). The only noteworthy 'setting' is, that I waited for a fully overcast day and thus diffuse lighting.


See the following video for the image series. Note how I moved the camera between each shot (in contrary to panoramic shots)

The goal is to capture each spot on at least three images. With difficult surfaces like this one, it is usually a good idea to overshoot, and I think, doubling the image number could have increased the resulting quality even more.


The following two photos depict the challenge of scanning glossy surfaces:

See how a slightly different viewing angle totally changes the lighting/reflections on the surface. The photogrammetry software will have a hard time finding corresponding features in both areas.


And of course, with the digital model it is very easy to create a 3d printed copy (15cm long) and printed on my Prusa MK3S+ in 8h.

Best regards,

Thomas




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