[2512.16705] Olaf: Bringing an Animated Character to Life in the Physical World

Computer Science > Robotics arXiv:2512.16705 (cs) [Submitted on 18 Dec 2025 (v1), last revised 2 Apr 2026 (this version, v2)] Title:Olaf: Bringing an Animated Character to Life in the Physical World Authors:David Müller, Espen Knoop, Dario Mylonopoulos, Agon Serifi, Michael A. Hopkins, Ruben Grandia, Moritz Bächer View a PDF of the paper titled Olaf: Bringing an Animated Character to Life in the Physical World, by David M\"uller and 6 other authors View PDF HTML (experimental) Abstract:Animated characters often move in non-physical ways and have proportions that are far from a typical walking robot. This provides an ideal platform for innovation in both mechanical design and stylized motion control. In this paper, we bring Olaf to life in the physical world, relying on reinforcement learning guided by animation references for control. To create the illusion of Olaf's feet moving along his body, we hide two asymmetric legs under a soft foam skirt. To fit actuators inside the character, we use spherical and planar linkages in the arms, mouth, and eyes. Because the walk cycle results in harsh contact sounds, we introduce additional rewards that noticeably reduce impact noise. The large head, driven by small actuators in the character's slim neck, creates a risk of overheating, amplified by the costume. To keep actuators from overheating, we feed temperature values as additional inputs to policies, introducing new rewards to keep them within bounds. We validate the efficacy of...