Jul 26, 2017 | By Benedict

A team of computer scientists and engineers from around the world has used Archimedes' ancient principle of water displacement to develop a new 3D scanning technique. The method can reconstruct hidden parts of an object that 3D laser scanners cannot capture.

A new water-based technique for 3D shape reconstruction has brought together researchers from universities all across the world, including Israel’s Tel-Aviv University and Ben-Gurion University, China’s Shandong University, and Canada’s University of British Columbia.

But the oldest contributor to this exciting 3D scanning project hails from none of these universities. He has also been dead for over 2,000 years.

That contributor is Archimedes, the Ancient Greek mathematician and physicist whose principle of water displacement has been utilized by the research group to invent a new 3D scanning method—one that overcomes the limitations of some of the most advanced techniques out there.

Archimedes principle states that “Any object, wholly or partially immersed in a stationary fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object.”

The new technique, described in a research paper titled “Dip Transform for 3D Shape Reconstruction,” uses that principle to turn modeling surface reconstruction into a volumetric problem.

The researchers say this offers big advantages, namely the ability to penetrate hidden areas of a 3D object that cameras and laser scanners would be unable to discern.

To make this happen, the researchers used a low-cost 3D dipping apparatus complete with robotic arm to submerge 3D objects in water.

By dipping a 3D object in the liquid along an axis, the scientists and engineers were able to measure the displacement of the liquid volume, forming it into a series of thin volume slices of the shape. When this was repeated across multiple angles, the researchers could eventually capture the entire geometry of the object.

When the object is dipped more often, more detail about its geometry can be extracted.

The dipping technique is somewhat similar to computed tomography—the technology used in hospital CT scanners—which uses optical systems to scan objects. Like the dipping technique, computed tomography involves taking many measurements from different angles, only the much more expensive (and potentially harmful) process uses X-rays instead of water.

Because of its low cost and high level of safety, the new water 3D scanning technique could appeal to scientists in numerous fields.

During the study, the method was demonstrated on a number of 3D models, including a hand balled up into a fist, a mother and child hugging, and a DNA double helix. Results showed the dip reconstructions to be almost as accurate as the original 3D models.

The method isn't perfect, however, and one obstacle to overcome involves air pockets. If an object lets water inside that doesn’t then flow freely out of it, the measurements will be skewed. However, the researchers are working on a way to overcome this problem, and may even be able to use the air pockets to find out extra information about an object’s shape.

The research project will be presented at the 2017 edition of SIGGRAPH, an annual conference for innovation in computer graphics research and interactive techniques, in Los Angeles, July 30 to August 3.

Authors of the study included Kfir Aberman, Tel Aviv University, Advanced Innovation Center for Future Visual Entertainment; Oren Katzir, Tel Aviv University, Advanced Innovation Center for Future Visual Entertainment; Qiang Zhou, Shandong University; Zegang Luo, Shandong University; Andrei Sharf, Advanced Innovation Center for Future Visual Entertainment, Ben-Gurion University of the Negev; Chen Greif, The University of British Columbia; Baoquan Chen, Shandong University; and Daniel Cohen-Or, Tel-Aviv University.



Posted in 3D Scanning



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