Browsing by Author "Wojtan, Chris"

Now showing 1 - 4 of 4
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    Coupling 3D Liquid Simulation with 2D Wave Propagation for Large Scale Water Surface Animation Using the Equivalent Sources Method
    (The Eurographics Association and John Wiley & Sons Ltd., 2022) Schreck, Camille; Wojtan, Chris; Chaine, Raphaëlle; Kim, Min H.
    This paper proposes a method for simulating liquids in large bodies of water by coupling together a water surface wave simulator with a 3D Navier-Stokes simulator. The surface wave simulation uses the equivalent sources method (ESM) to efficiently animate large bodies of water with precisely controllable wave propagation behavior. The 3D liquid simulator animates complex non-linear fluid behaviors like splashes and breaking waves using off-the-shelf simulators using FLIP or the level set method with semi-Lagrangian advection. We combine the two approaches by using the 3D solver to animate localized non-linear behaviors, and the 2D wave solver to animate larger regions with linear surface physics. We use the surface motion from the 3D solver as boundary conditions for 2D surface wave simulator, and we use the velocity and surface heights from the 2D surface wave simulator as boundary conditions for the 3D fluid simulation. We also introduce a novel technique for removing visual artifacts caused by numerical errors in 3D fluid solvers: we use experimental data to estimate the artificial dispersion caused by the 3D solver and we then carefully tune the wave speeds of the 2D solver to match it, effectively eliminating any differences in wave behavior across the boundary. To the best of our knowledge, this is the first time such a empirically driven error compensation approach has been used to remove coupling errors from a physics simulator. Our coupled simulation approach leverages the strengths of each simulation technique, animating large environments with seamless transitions between 2D and 3D physics.
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    Making Procedural Water Waves Boundary-aware
    (The Eurographics Association and John Wiley & Sons Ltd., 2020) Jeschke, Stefan; Hafner, Christian; Chentanez, Nuttapong; Macklin, Miles; Müller-Fischer, Matthias; Wojtan, Chris; Bender, Jan and Popa, Tiberiu
    The ''procedural'' approach to animating ocean waves is the dominant algorithm for animating larger bodies of water in interactive applications as well as in off-line productions - it provides high visual quality with a low computational demand. In this paper, we widen the applicability of procedural water wave animation with an extension that guarantees the satisfaction of boundary conditions imposed by terrain while still approximating physical wave behavior. In combination with a particle system that models wave breaking, foam, and spray, this allows us to naturally model waves interacting with beaches and rocks. Our system is able to animate waves at large scales at interactive frame rates on a commodity PC.
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    Pacific Graphics 2022 - CGF 41-7: Frontmatter
    (The Eurographics Association and John Wiley & Sons Ltd., 2022) Umetani, Nobuyuki; Wojtan, Chris; Vouga, Etienne; Umetani, Nobuyuki; Wojtan, Chris; Vouga, Etienne
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    A Practical Method for Animating Anisotropic Elastoplastic Materials
    (The Eurographics Association and John Wiley & Sons Ltd., 2020) Schreck, Camille; Wojtan, Chris; Panozzo, Daniele and Assarsson, Ulf
    This paper introduces a simple method for simulating highly anisotropic elastoplastic material behaviors like the dissolution of fibrous phenomena (splintering wood, shredding bales of hay) and materials composed of large numbers of irregularly-shaped bodies (piles of twigs, pencils, or cards). We introduce a simple transformation of the anisotropic problem into an equivalent isotropic one, and we solve this new ''fictitious'' isotropic problem using an existing simulator based on the material point method. Our approach results in minimal changes to existing simulators, and it allows us to re-use popular isotropic plasticity models like the Drucker-Prager yield criterion instead of inventing new anisotropic plasticity models for every phenomenon we wish to simulate.