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January 2020

Producing 3D models using photogrammetry

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DXT describes how various components were 3D reconstructed using photogrammetry.

The HR-Recycler project will implement learning paradigms in virtual reality (VR) settings, for which a recycling plant will be modelled in 3D to be displayed in a VR environment. One objective is to capture accurately the interaction of the workers with the environment and especially the objects present in the factory. Another objective is to allow workers to practice disassembly procedures and to properly interact with the environment. It is necessary to deliver a VR environment as realistic as possible, i.e. as close as possible to an actual recycling factory. To model accurately complex shapes or objects, one may use a full manual technique with tools such as 3DSmax. However, this technique is quite complex and time consuming. Imagine how long it could take to model a PC motherboard entirely manually, given the number of small elements (diodes, capacitors, etc.)

Photogrammetry is a 3D reconstruction technique that allows to produce 3D models of complex shapes much more quickly. It consists in taking dozens of pictures of an object from as many viewing angle as possible, then using an algorithm to reconstruct the object from all those pictures. Although it generally gives good results for complex shapes, it often fails for simple ones. The main reason is that simple shapes have very few points of interests that de algorithm may use for 3D reconstruction. Also, simple surfaces are often too mate or too bright, leading to reconstruction errors. To illustrate this, a 3D reconstruction of the above motherboard is shown in the figure below.

To overcome limitations of both techniques, DIGINEXT has set-up a 3D modelling technique that combines manual modelling and photogrammetry to produce more rapidly accurate models of WEEE. In the example of a PC case, the simple parts (e.g. exterior of the case, flat surfaces) were manually modelled using 3DSmax, whereas internal complex shapes were modelled using photogrammetry. This allowed to produce a full 3D model of a PC case more rapidly than using a 3D CAD tool only and more precisely than by using photogrammetry alone. Several objects have been created using these techniques, as shown in the pictures below and will be used in the virtual factory for the next steps of the project.