vriphys18

Permanent URI for this collection

https://diglib.eg.org/handle/10.2312/2632166

Browse

Browsing vriphys18 by Subject "Physical simulation"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Laplacian Damping for Projective Dynamics
    (The Eurographics Association, 2018) Li, Jing; Liu, Tiantian; Kavan, Ladislav; Andrews, Sheldon and Erleben, Kenny and Jaillet, Fabrice and Zachmann, Gabriel
    Damping is an important ingredient in physics-based simulation of deformable objects. Recent work introduced new fast simulation methods such as Position Based Dynamics and Projective Dynamics. Explicit velocity damping methods currently used in conjunction with Position Based Dynamics or Projective Dynamics are simple and fast, but have some limitations. They may damp global motion or non-physically transport velocities throughout the simulated object. More advanced damping models do not have these limitations, but are slow to evaluate, defeating the benefits of fast solvers such as Projective Dynamics. We present a new type of damping model specifically designed for Projective Dynamics, which provides the quality of advanced damping models while adding only minimal computing overhead. The key idea is to define damping forces using Projective Dynamics' Laplacian matrix. In a number of simulation examples we show that this damping model works very well in practice. When used with a modified Projective Dynamics solver that uses a non-dissipative implicit midpoint integrator, our damping method provides fully user-controllable damping, allowing the user to quickly produce visually pleasing and vivid animations.
  • Thumbnail Image
    Item
    MLS Pressure Extrapolation for the Boundary Handling in Divergence-Free SPH
    (The Eurographics Association, 2018) Band, Stefan; Gissler, Christoph; Peer, Andreas; Teschner, Matthias; Andrews, Sheldon and Erleben, Kenny and Jaillet, Fabrice and Zachmann, Gabriel
    We propose a novel method to predict pressure values at boundary particles in incompressible divergence-free SPH simulations (DFSPH). Our approach employs Moving Least Squares (MLS) to predict the pressure at boundary particles. Therefore, MLS computes hyperplanes that approximate the pressure field at the interface between fluid and boundary particles. We compare this approach with two previous techniques. One previous technique mirrors the pressure from fluid to boundary particles. The other one extrapolates the pressure from fluid to boundary particles, but uses a gradient that is computed with Smoothed Particle Hydrodynamics (SPH). We motivate that gradient-based extrapolation is more accurate than mirroring. We further motivate that our proposed MLS gradient is less error prone than the SPH gradient at the boundary. In our experiments, we indicate artifacts in previous approaches. We show that these artifacts are significantly reduced with our approach resulting in simulation steps that can be twice as large compared to previous methods. We further present challenging and complex scenarios to illustrate the capabilities of the proposed boundary handling.
  • Thumbnail Image
    Item
    Quantitative Validation of Physically Based Deformable Models in Computer Graphics
    (The Eurographics Association, 2018) Banks, Matthew K.; Hazel, Andrew L.; Riley, Graham D.; Andrews, Sheldon and Erleben, Kenny and Jaillet, Fabrice and Zachmann, Gabriel
    This paper presents a novel software framework for quantitative validation of physically-based deformable models in computer graphics. In the majority of previous studies, validation is qualitative (through visual plausibility), which is necessarily user subjective. The proposed framework facilitates construction of a single scalar output that quantifies the agreement between the complete time histories of test and reference models. Different models and comparison metrics can be easily included within the general framework. The framework is shown to yield a high accuracy score for a simplified model that can be analytically derived from the reference model, indicating that the framework is reliable. A lower score results when evaluating a more approximate, yet still visually plausible, model, demonstrating the objective sensitivity of the framework. The software framework can thus provide an objective measure of accuracy and a standardised way to quantitatively compare the accuracy of one method against another, whilst also supplying a quantitative rationale for trading accuracy and performance.
  • Thumbnail Image
    Item
    Real-Time Virtual Pipes Simulation and Modeling for Small-Scale Shallow Water
    (The Eurographics Association, 2018) Dagenais, Francois; Guzman, Julián; Vervondel, Valentin; Hay, Alexander; Delorme, Sébastien; Mould, David; Paquette, Eric; Andrews, Sheldon and Erleben, Kenny and Jaillet, Fabrice and Zachmann, Gabriel
    We propose an approach for real-time shallow water simulation, building upon the virtual pipes model with multi-layered heightmaps. Our approach introduces the use of extended pipes which resolve flow through fully-flooded passages, which is not possible using current multi-layered techniques. We extend the virtual pipe method with a physically-based viscosity model that is both fast and stable. Our viscosity model is integrated implicitly without the expense of solving a large linear system. The liquid is rendered as a triangular mesh surface built from a heightmap. We propose a novel surface optimization approach that prevents interpenetrations of the liquid surface with the underlying terrain geometry. To improve the realism of small-scale scenarios, we present a meniscus shading approach that adjusts the liquid surface normals based on a distance field. Our approach runs in real time on various scenarios of roughly 10 x 10 cm at a resolution of 0.5 mm, with up to five layers.