Profiling

The silhouette of an object is isolated from a monochromic background by chroma-keying of its digital picture. 2D Silhouettes are created from a series of pictures taken from different viewing angles, realised by turning the object on a turning table. These silhouettes are then used to compute a 3D point cloud representing the 3D geometry of the object.

The software describes the 3D data in the format of a wireframe. The colour and texture of the different object parts is available in the taken pictures. This texture information is mapped onto the polygons that form the ‘building blocks’ of the wireframe. The method is rather robust, but concavities can not be handled.

Concavities occur when holes in a surface, or empty spaces behind parts that are situated in front, are not seen in the silhouette profile, and thus lead to amorphous ‘blobs’. Removing these artefacts by 3D editing software is very time-consuming. Another disadvantage of the profiling method is its difficulty to register thin objects like twigs and petioles The final 3D image may not show the twigs if the twig silhouettes do not match between the different viewpoint images and subsequent merging may not produce a shape but only emptiness.

Scanstation for the profiling method (left) and one of a serie of pictures of Arabidopsis (right).