REAP is a robotic platform with a 5-DOF manipulator (Figure 1) consisting of a x-y-z axis translational mechanism holding a robot gripper with an additional z-axis rotation DOF. The 5th DOF is provided by the tilting of the brush pen. Together, the 5 DOFs serve to provide the dexterity for emulating the fine hand and wrist motions of executing Chinese brush strokes. The DOFs are all independently commanded, doing away with the kinematics problems associated with many robotic systems. The input commands are executed through a PID type controller.
Figure 2 shows an additional mechanism on the manipulator containing a servomotor and a brush holder to lock and rotate the brush pen along its axis. The mechanism cannot improve the working DOFs of the brush pen, but the induced axial brush rotary motion would enable the removal of excessive ink from the brush and the straightening of its hair when needed, both essential in performing Chinese brush artistry.
So far, REAP is capable of automated line stroke drawing upon the input of a proper image. The system is also capable of conducting vision-based iterative drawing. This means that the current executed drawing is compared with the original image to “intelligently” deduce the “imperfections” herein. Information from the comparison will thus be applied in the next execution for improved quality. Figure 3 shows a line drawing executed by REAP and its comparison with the original. For full stroke calligraphy, the system is able to decompose given characters into individual strokes, and then generate the needed commands to replicate the given characters. Figure 4, 5 and 6 present three works executed by REAP. The originals are also shown for comparison.
For now, the developed algorithms do not distinguish between execution of calligraphy and painting. This is why in the execution of the Chinese calligraphies, there are mistakes in the order of executing the stroke elements, something considered important in Chinese writing. We will try to improve in this regard in future work. We are also in the process of building a setup so we can invite Chinese calligraphers and painters to come into our laboratory for real time recordings of their brush motions during the execution of their artworks. The database collected will serve in future studies of analyzing and rendering the various styles of the artists.