Toronto: Already being used for delivering packages and monitoring wild life, unmanned aerial vehicles (UAVs) may soon be used for painting murals outdoors. A team led by Paul Kry from McGill University's school of computer science programmed tiny drones to create dot drawings -- an artistic technique known as stippling. "I thought it would be great to have drones paint portraits of famous computer scientists on them," Kry said. Stippling is the creation of a pattern simulating varying degrees of solidity or shading by using small dots. The drones are so small that they fit in the palm of a hand and so light that even very slight air currents can toss the drones off course. They are fitted with a miniature arm that holds an ink-soaked sponge. As they hover near the surface to be painted, internal sensors and a motion capture system help position them to dab the ink in just the right places. Although programming the aerial robots to apply each payload of ink accurately and efficiently required complex algorithms to plan flight paths, the team was able to address this problem. So far, the flying robots have rendered -- on paper -- portraits of Alan Turing, Grace Kelly and Che Guevara, among others. Each drawing is composed of a few hundred to a few thousand black dots of varying sizes. Kry noted that eventually larger drones could be deployed to paint murals on hard-to-reach outdoor surfaces, including curved or irregular facades. An article on the project by Kry and the three students won a best paper prize at an international symposium in Lisbon on computational aesthetics in graphics and imaging recently.