Browsing by Author "Lee, Jehee"

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    Figure Skating Simulation from Video
    (The Eurographics Association and John Wiley & Sons Ltd., 2019) Yu, Ri; Park, Hwangpil; Lee, Jehee; Lee, Jehee and Theobalt, Christian and Wetzstein, Gordon
    Figure skating is one of the most popular ice sports at the Winter Olympic Games. The skaters perform several skating skills to express the beauty of the art on ice. Skating involves moving on ice while wearing skate shoes with thin blades; thus, it requires much practice to skate without losing balance. Moreover, figure skating presents dynamic moves, such as jumping, artistically. Therefore, demonstrating figure skating skills is even more difficult to achieve than basic skating, and professional skaters often fall during Winter Olympic performances. We propose a system to demonstrate figure skating motions with a physically simulated human-like character. We simulate skating motions with non-holonomic constraints, which make the skate blade glide on the ice surface. It is difficult to obtain reference motions from figure skaters because figure skating motions are very fast and dynamic. Instead of using motion capture data, we use key poses extracted from videos on YouTube and complete reference motions using trajectory optimization. We demonstrate figure skating skills, such as crossover, three-turn, and even jump. Finally, we use deep reinforcement learning to generate a robust controller for figure skating skills.
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    Functionality‐Driven Musculature Retargeting
    (© 2021 Eurographics ‐ The European Association for Computer Graphics and John Wiley & Sons Ltd, 2021) Ryu, Hoseok; Kim, Minseok; Lee, Seungwhan; Park, Moon Seok; Lee, Kyoungmin; Lee, Jehee; Benes, Bedrich and Hauser, Helwig
    We present a novel retargeting algorithm that transfers the musculature of a reference anatomical model to new bodies with different sizes, body proportions, muscle capability, and joint range of motion while preserving the functionality of the original musculature as closely as possible. The geometric configuration and physiological parameters of musculotendon units are estimated and optimized to adapt to new bodies. The range of motion around joints is estimated from a motion capture dataset and edited further for individual models. The retargeted model is simulation‐ready, so we can physically simulate muscle‐actuated motor skills with the model. Our system is capable of generating a wide variety of anatomical bodies that can be simulated to walk, run, jump and dance while maintaining balance under gravity. We will also demonstrate the construction of individualized musculoskeletal models from bi‐planar X‐ray images and medical examination.
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    Multi‐Segment Foot for Human Modelling and Simulation
    (© 2020 Eurographics ‐ The European Association for Computer Graphics and John Wiley & Sons Ltd, 2020) Park, Hwangpil; Yu, Ri; Lee, Jehee; Benes, Bedrich and Hauser, Helwig
    Realistic modelling of a human‐like character is one of the main topics in computer graphics to simulate human motion physically and also look realistically. Of the body parts, a human foot interacts with the ground, and plays an essential role in weight transmission, balancing posture and assisting ambulation. However, in the previous researches, the foot model was often simplified into one or two rigid bodies connected by a revolute joint. We propose a new foot model consisting of multiple segments to reproduce human foot shape and its functionality accurately. Based on the new model, we develop a foot pose controller that can reproduce foot postures that are generally not obtained in motion capture data. We demonstrate the validity of our foot model and the effectiveness of our foot controller with a variety of foot motions in a physics‐based simulation.
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    Pacific Conference on Computer Graphics and Applications - Short Papers 2019: Frontmatter
    (Eurographics Association, 2019) Lee, Jehee; Theobalt, Christian; Wetzstein, Gordon; Lee, Jehee and Theobalt, Christian and Wetzstein, Gordon
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    Pacific Conference on Computer Graphics and Applications 2019 - CGF38-7: Frontmatter
    (The Eurographics Association and John Wiley & Sons Ltd., 2019) Lee, Jehee; Theobalt, Christian; Wetzstein, Gordon; Lee, Jehee and Theobalt, Christian and Wetzstein, Gordon