SCA 2020: Showcases

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https://diglib.eg.org/handle/10.2312/2632938

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    Contact and Human Dynamics from Monocular Video
    (The Eurographics Association, 2020) Rempe, Davis; Guibas, Leonidas J.; Hertzmann, Aaron; Russell, Bryan; Villegas, Ruben; Yang, Jimei; Holden, Daniel
    Existing methods for human motion from video predict 2D and 3D poses that are approximately accurate, but contain visible errors that violate physical constraints, such as feet penetrating the ground and bodies leaning at extreme angles. We present a physics-based method for inferring 3D human motion from video sequences that takes initial 2D and 3D pose estimates as input. We first estimate ground contact timings with a neural network which is trained without hand-labeled data. A physicsbased trajectory optimization then solves for a physically-plausible motion, based on the inputs. We show this process produces motions that are more realistic than those from purely kinematic methods for character animation from dynamic videos. A detailed report that fully describes our method is available at geometry.stanford.edu/projects/human-dynamics-eccv-2020.
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    Negative Jacobian Free Simulations Using Principal Stretches
    (The Eurographics Association, 2020) Francu, Mihail; Holden, Daniel
    Finite element (FE) simulations are prone to encountering negative Jacobians during the solving process. If nothing is done, the simulation can be brought to a halt, result in inverted elements or have undetermined behavior. We propose a solution that uses principal stretches as slack variables in a constrained minimization formulation and enforce them to always be positive. We show that our approach can never hit inverted configurations, thus being suitable for applications where inversion cannot be tolerated. We implement the method in 2D and show that it outperforms standard FE methods in stressful scenarios.
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    WeightShift: Accelerating Animation at Framestore with Physics
    (The Eurographics Association, 2020) Chapman, Danny; Daoust, Tim; Ormos, Andras; Lewis, Joseph; Holden, Daniel
    Framestore and WeightShift created a full-body physics simulation to deliver art-directed shots in highly dynamic scenarios in several days instead of several weeks. Our technique combines ragdoll simulation and keyframe animation in a new control scheme that is integrated in a standard Maya rig to produce a hybrid simulation workflow. The new workflow was used in over 50 completed shots, and is in production on numerous current projects. In this session we share our experience with full-body simulation, and discuss the numerous advantages and challenges of the technique.
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    ZooBuilder: 2D and 3D Pose Estimation for Quadrupeds Using Synthetic Data
    (The Eurographics Association, 2020) Fangbemi, Abassin Sourou; Lu, Yi Fei; Xu, Maoyuan; Luo, Xiaowu; Rolland, Alexis; Raissi, Chedy; Holden, Daniel
    This work introduces a novel strategy for generating synthetic training data for 2D and 3D pose estimation of animals using keyframe animations. With the objective to automate the process of creating animations for wildlife, we train several 2D and 3D pose estimation models with synthetic data, and put in place an end-to-end pipeline called ZooBuilder. The pipeline takes as input a video of an animal in the wild, and generates the corresponding 2D and 3D coordinates for each joint of the animal's skeleton. With this approach, we produce motion capture data that can be used to create animations for wildlife.
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    Fast Eulerian Fluid Simulation In Games Using Poisson Filters
    (The Eurographics Association, 2020) Rabbani, Amir H.; Khiat, Soufiane; Holden, Daniel
    We present separable Poisson filters to accelerate the projection step in Eulerian fluid simulation. These filters are analytically computed offline and are easy to integrate into any fluid algorithm with a Poisson pressure computation step. We take advantage of the recursive structure of the Jacobi method to construct and then reduce a kernel that is used to solve the Poisson pressure entirely on GPU. Our method demonstrates promising speedups that scale well with both the grid resolution and the target Jacobi iteration.