Browsing by Author "Ko, Hyeong-Seok"

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    A Practical Approach to Physically-Based Reproduction of Diffusive Cosmetics
    (The Eurographics Association and John Wiley & Sons Ltd., 2018) Kim, Goanghun; Ko, Hyeong-Seok; Fu, Hongbo and Ghosh, Abhijeet and Kopf, Johannes
    In this paper, we introduce so-called the bSX method as a new way to utilize the Kubelka-Munk (K-M) model. Assuming the material is completely diffusive, the K-M model gives the reflectance and transmittance of the material from the observation of the material applied on a backing, where the observation includes the thickness of the material application. By rearranging the original K-M equation, we propose that the reflectance and transmittance can be calculated without knowing the thickness. This is a practically useful contribution. Based on the above finding, we develop the bSX method which can (1) capture the material specific parameters from the two photos - taken before and after the material application, and (2) reproduce its effect on a novel backing. We experimented the proposed method in various cases related to virtual cosmetic try-on, which include (1) capture from a single color backing, (2) capture from human skin backing, (3) reproduction of varying thickness effect, (4) reproduction of multi-layer cosmetic application effect, (5) applying the proposed method to makeup transfer. Compared to previous image-based makeup transfer methods, the bSX method reproduces the feel of the cosmetics more accurately.
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    Tight Normal Cone Merging for Efficient Collision Detection of Thin Deformable Objects
    (The Eurographics Association, 2021) Han, Dong-Hoon; Lee, Chang-Jin; Lee, Sangbin; Ko, Hyeong-Seok; Theisel, Holger and Wimmer, Michael
    When simulating thin deformable objects such as clothes, collision detection alone takes a lot of computation. One way of reducing the computation is culling false-positives as much as possible. In the context of bounding volume hierarchy, Provot proposed a culling method that is based on hierarchical merging of normal enclosing cones. In this work, we investigate Provot's merging algorithm and show that there is some room for improvement. We propose a new merging algorithm, in the context of discrete collision detection, which always produces an equal or tighter mergence than Provot's merging. We extend the above algorithm so that it can be used in the context of continuous collision detection. Experiments show that the proposed method makes about 25% reduction in the number of triangle pairs for which vertex-triangle or edge-edge collision test has to be performed, and 18% reduction in time for collision detection.