Random Polygonal Train Horizontal/Vertical is a very early drawing of generative art by global standards. It was calculated on the computer Standard Elektrik-Lorenz ER56, and drawn on the drawing machine Zuse Graphomat Z64. The marking '128/150' on the reverse indicates that it is a sheet from an edition. However, this is not a print of an original (as in printmaking), but rather each of the 150 drawings was drawn separately by the drawing machine. Each of the sheets produced in this way is therefore an original and unique drawing. The drawing process itself took about 15 minutes under the technical conditions prevailing at the time.
It is reasonably easy to see that a line pattern of alternating horizontal and vertical lines was drawn four times. This is due to a simple feature of the Graphomat drawing machine. Up to four drawing pens could be inserted into it at the same time. For the present sheet, four pens were inserted and lowered at the same time, so that the line pattern was produced four times in the mechanical process of drawing, parallel to each other and in three colours. This is probably easiest to follow visually on the wider black line pattern. I have always used professional drawing pencils and inks, as well as papers from art supplies.
The drawing thus consists of four geometrically identical lines that are graphically realised parallel to each other. In mathematics, such a line is called a "polygon" (meaning "many-sided"). Each of the individual line segments of the polygon is of random length (remaining within the drawing format). The decision whether to draw to the left or to the right (in the horizontal case), or upwards or downwards (in the vertical case) is also random. The location of the first point is random, as is the first direction (horizontal or vertical) and the number of segments of the entire polygon. —Frieder Nake