RAP (Robotic Action Painter), created in 2006 for the Museum of Natural History in New York, is an individualist artist and not a swarm, but makes use of the same composition methods based on stigmergy and emergence. This robot is additionally able to determine, by its own means, the moment in which the painting is finished. Previous versions didn't have this capacity being conditioned by battery discharge or my will to stop the process. RAP's decision is taken based on the information that it gathers directly from the painting, what produces a considerable variation of time and form, since RAP can decide that the work is complete after a relatively short while (entailing accordingly a low pictorial expression) or can extend the picture construction for a quite long period, making it much more dense and complex. The "secret" of this behavior is in the significant change of the sensors, which passed from two to nine "eyes", allowing now the reading of local patterns, in addition to color spots. RAP is also my first robot to sign its works.
RAP has a set of sensors to avoid obstacles, to perceive the presence of visitors near the case, to check the paper, and most important to detect color. A total of 9 RGB color sensors, located under the robot body and disposed in a 3 x 3 grid, permanently scans an area of approximately 3 cm2. RAP will be operating under a Random Mode until a certain amount of color (threshold) is detected. In this mode the robot makes a kind of sketch, randomly drawing a series of lines. The shape, size, direction and color of these lines are also drawn in a randomly way. In this sense it never produces the same lines or the same combination of lines.
In the Random Mode in order to generate a truly random number for the seed, RAP gets it from its relative direction measured by an onboard compass.
When the color detected exceeds the threshold, RAP changes to a Reactive Mode. It will be drawing on this mode until it finishes the painting, never getting back to the previous mode of operation.
Under the Reactive Mode RAP only draws in those parts of the drawing where the color exceeds the given threshold. Therefore it tends to generate color clusters on some areas.
Making use of its color sensor grid RAP decides when the work is ready. That happens when a certain pattern is detected with all of the 9 sensors. It then goes to the corner and signs with its own name.
After signing, the robot moves to the center of the paper, starts flashing its lights and sends a wireless signal to the paper machine. This machine, installed on the bottom part of the box case, advances the paper roll, feeding the table with a fresh sheet for a new drawing.