But the researchers say that while this approach may work well in theory and in simulations, once it comes time to run the program in a robot, the computational burden and real-world variability make it impractical to consider the details of every step from the get-go. “You have to introduce an approximation to get some tractability. You have to say, ‘Whichever way this works out, I’m going to be able to deal with it,’” Lozano-Pérez says.