Symmetry of Objects in Photogrammetry

The symmetry of movable elements, like the „donkey,“ presented a challenge during the digitization of the 1932 pop-up book „The Pop-up Pinocchio.“ These elements, when the page was opened, were almost identical on both sides, which made it  difficult for photogrammetry software to correctly assign the photos to the appropriate positions in the 3D model. Lack of unique features : Photogrammetry relies on detecting and matching characteristic points (key points) between images. When an object is nearly identical on both sides, algorithms struggle to assign these points, they may incorrectly match features from the left and right sides.This can sometimes cause two overlapping 3D reconstructions, even without any camera movement.