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Diagram of mapping and reconstruction/interpretation Classical descriptive geometry can be used for making an axonometric image Oc of an object O. Usually we understand such an image Oc as a parallel projection of O. (The axonometric imaging principle yields in a How true is true-3D? – Geometry between Single Image Stereograms and Lenticular Foil Displays 29 wider sense and can be connected with central projections, too. ) In our society we are well trained to “read” oblique parallel projections of an object O and will intuitively understand parallelity of lines in the image plane as stemming from parallel lines in space.

Naïve viewers will hardly find the unexpected objects O, which will correspond to the images and they will always find it a geometer’s trick when they are shown the actual physical 3D objects. g. Fig. 5. Here a planar picture “must” be interpreted as an image of a 3D object. But there are two partial solutions for such an “impossible” object. Psychological facts and maybe our image- and paperbased education let the painting less probably occur just as a planar colour scheme then an image of something three-dimensional.

In the future, 3D visualization by means of LFD will gain increased importance not only for cartography. One can suppose that advanced advertisement will soon use this technique, too, and even for technical handbooks and assembly instructions LFD can be useful. For the moment accuracy problems arise from cartography alone. However, also the private sector with the wish to “three-dimensionalise” its photographs poses demands on accuracy. LFD representation of an object O still is cheaper than its physical representation by Rapid Prototyping.