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    Time-Reversed Art Directable Smoke Simulation
    (The Eurographics Association, 2018) Oborn, Jeremy; Flynn, Sean; Egbert, Parris; Holladay, Seth; Diamanti, Olga and Vaxman, Amir
    Physics-based fluid simulation often produces unpredictable behavior that is difficult for artists to control. We present a new method for art directing smoke animation using time-reversed simulation. Given a final fluid configuration, our method steps backward in time generating a sequence that, when played forward, is visually similar to traditional forward simulations. This allows artists to create simulations with fast turnaround times that match an exact art-directed shape at any timestep of the simulation. We address a number of challenges associated with time-reversal including the problem of decreasing entropy.
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    Iterative Carving for Self-supporting 3D Printed Cavities
    (The Eurographics Association, 2018) Hornus, Samuel; Lefebvre, Sylvain; Diamanti, Olga and Vaxman, Amir
    Additive manufacturing technologies fabricate objects layer by layer, adding material on top of already solidified layers. A key challenge is to ensure that there is always material below, for otherwise added material simply falls under the effect of gravity. This is a critical issue with most technologies, and with fused filament in particular. In this work we investigate how to compute as large as possible empty cavities which boundaries are self-supporting. Our technique is based on an iterated carving algorithm, that is fast to compute and produces nested sets of inner walls. The walls have exactly the minimal printable thickness of the manufacturing process everywhere. Remarkably, our technique is out-of-core, sweeping through the model from the top down. Using our approach, we can print large objects using as little as a single filament thickness for the boundary, providing one order of magnitude reduction in print time and material use while guaranteeing printability.