Sim-to-real

Training in simulation is fast and safe: thousands of virtual robots can practice walking at once, and none of them breaks. The difficulty is that the simulated world is never exact, so a policy that works on screen may stumble on a real floor.

Many quadruped and humanoid walking skills now come from sim-to-real training, which is why robot dogs can run over grass and stairs. When reading specs, ask whether the claimed terrain skills were tested on the physical robot, not only in the simulator.