Category: Uncategorized

Nathan Mitchell, Court Cutting, Eftychios Sifakis

We present an interactive simulation framework for authoring surgical procedures of soft tissue manipulation using physics-based simulation to animate the flesh. This interactive authoring tool can be used by clinical educators to craft three-dimensional illustrations of the intricate maneuvers involved in craniofacial repairs, in contrast to two-dimensional sketches and still photographs which are the medium used to describe these procedures in the traditional surgical curriculum. Our virtual environment also allows surgeons-intraining to develop cognitive skills for craniofacial surgery by experimenting with different approaches to reconstructive challenges, adapting stock techniques to flesh regions with nonstandard shape, and reach preliminary predictions about the feasibility of a given repair plan. We use a Cartesian grid-based embedded discretization of nonlinear elasticity to maximize regularity, and expose opportunities for aggressive multithreading and SIMD accelerations. Using a grid-based approach facilitates performance and scalability, but constrains our ability to capture the topology of thin surgical incisions. We circumvent this restriction by hybridizing the grid-based discretization with an explicit hexahedral mesh representation in regions where the embedding mesh necessitates overlap or nonmanifold connectivity. Finally, we detail how the front-end of our system can run on lightweight clients, while the core simulation capability can be hosted on a dedicated server and delivered as a network service.

GRIDiron: An interactive authoring and cognitive training foundation for reconstructive plastic surgery procedures

Xinxin Zhang, Robert Bridson, Chen Greif

Most visual effects fluid solvers use a time-splitting approach where velocity is first advected in the flow, then projected to be incompressible with pressure. Even if a highly accurate advection scheme is used, the self-advection step typically transfers some kinetic energy from divergence-free modes into divergent modes, which are then projected out by pressure, losing energy noticeably for large time steps. Instead of taking smaller time steps or using significantly more complex time integration, we propose a new scheme called IVOCK (Integrated Vorticity of Convective Kinematics) which cheaply captures much of what is lost in self-advection by identifying it as a violation of the vorticity equation. We measure vorticity on the grid before and after advection, taking into account vortex stretching, and use a cheap multigrid V-cycle approximation to a vector potential whose curl will correct the vorticity error. IVOCK works independently of the advection scheme (we present examples with various semi-Lagrangian methods and FLIP), works independently of how boundary conditions are applied (it just corrects error in advection, leaving pressure etc.\ to take care of boundaries and other forces), and other solver parameters (we provide smoke, fire, and water examples). For 10~25% extra computation time per step much larger steps can be used, while producing detailed vorticial structures and convincing turbulence that are lost without correction.

Restoring the Missing Vortices in Advection-Projection Fluid Solvers

It’s my favourite time of the year. Stay tuned for more simulation paper links as they appear. As usual, see Ke-Sen Huang’s page for the full list.

• A Stream Function Solver for Liquid Simulations
• Power Particles: An incompressible fluid solver based on power diagrams
• Double Bubbles Sans Toil and Trouble: Discrete Circulation-Preserving Vortex Sheets for Soap Films and Foams
• Air Meshes for Robust Collision Handling
• Fast Grid-Free Surface Tracking
• Deformation Capture and Modeling of Soft Objects
• Restoring the Missing Vortices in Advection Projection Fluid Solvers
• Subspace Condensation: Full Space Adaptivity for Subspace Deformations
• Co-Dimensional Non-Newtonian Fluids
• The Affine Particle-In-Cell Method
• Simulating Rigid Body Fracture with Surface Meshes
• GRIDiron: An interactive authoring and cognitive training foundation for reconstructive plastic surgery procedures
• High-Resolution Brittle Fracture Simulation with Boundary Elements
• Stable Constrained Dynamics
• Data-Driven Finite elements for Geometry and Material Design
• LazyFluids: Appearance Transfer for Fluid Animations
• Nonlinear Material Design Using Principal Stretches
• OmniAD: Data-Driven Omni-Directional Aerodynamics
• An Implicit Viscosity Formulation for SPH Fluids
• Fluid-Volume Modeling from Sparse Multi-View Images by Appearance Transfer
• Biomechanical Simulation and Control of Hands and Tendinous Systems
• A Perceptual Control Space for Garment Simulation
• Dyna: A Model of Dynamic Human Shape in Motion

 

TOG papers:

• Water Wave Animation via Wavefront Parameter Interpolation
• Realistic Biomechanical Simulation and Control of Human Swimming
• Real-Time Nonlinear Shape Interpolation
• Robust Simulation of Sparsely Sampled Thin Features in SPH-Based Free Surface Flows

Physics-based animation papers at Eurographics 2015:

• A Dimension-reduced Pressure Solver for Liquid Simulations
• Implicit Formulation for SPH-based Viscous Fluids
• Scalable Partitioning for Parallel Position Based Dynamics
• A Cut-Cell Geometric Multigrid Poisson Solver for Fluid Simulation
• Real-Time Subspace Integration for Example-Based Elastic Material

The SIGGRAPH Asia 2014 collection includes:

• Yarn-level Simulation of Woven Cloth
• A PPPM Fast Summation Method for Fluids and Beyond
• Fast and Exact Continuous Collision Detection with Bernstein Sign Classification
• SPGrid: A Sparse Paged Grid Structure Applied to Adaptive Smoke Simulation
• Windy Trees: Computing Stress Response for Developmental Tree Models

 

Transactions on Graphics, to be presented at SIG Asia:

• Multiple-Fluid SPH Simulation Using a Mixture Model

I’ve been slow in getting this list together, so without further ado:

• Continuous Collision Detection Between Points and Signed Distance Fields
• Massively Parallel Batch Neural Gas for Bounding Volume Hierarchy Construction
• Massively-Parallel Proximity Queries for Point Clouds
• Efficient Transfer of Contact-Point Local Deformations in Data-Driven Simulations Using Hermitian Moments
• A unified topological-physical model for adaptive refinement
• A p-Multigrid Algorithm using Cubic Finite Elements for Efficient Deformation Simulation
• Mechanical modelling of three-dimensional plant tissue indented by a probe
• Controlling the Shape and Motion of Plumes in Explosion Simulations
• SutureHap: a Suture Simulator with Haptic Feedback
• Information Fusion for Real-time Motion Estimation in Image-guided Breast Biopsy Navigation
• Virtual Fitting Pipeline: Body Dimension Recognition, Cloth Modelling, and On-Body Simulation
• Coupling Hair with Smoothed Particle Hydrodynamics Fluids
• A Parallel Architecture for IISPH Fluids
• An Improved Jacobi Solver for Particle Simulation
• Parallel Particles: A Parallel Position Based Approach for Fast and Stable Simulation of Granular Materials
• Laplacian Cut-Maps for Real-Time Deformables
• Variable stiffness haptic interface controlled through Inverse simulation

If anyone has links to the associated papers for the (many) missing ones, please let me know!

Nobuyuki Umetani, Ryan Schmidt, Jos Stam

We present a novel method to simulate complex bending and twisting of elastic rods. Elastic rods are commonly simulated using force based methods, such as the finite element method. These methods are accurate, but do not directly fit into the more efficient position-based dynamics framework, since the definition of material frames are not entirely based on positions. We introduce ghost points, which are additional points defined on edges, to naturally endow continuous material frames on discretized rods. We achieve robustness by a novel discretization of the Cosserat theory. The method supports coupling with a frame, a triangle, and a rigid body at the rod’s end point. Our formulation is highly efficient, capable of simulating hundreds of strands in real-time.

Position-Based Elastic Rods

Physical simulation papers:

• Ocean Waves Animation using Boundary Integral Equations and Explicit Mesh Tracking
• View-Dependent Adaptive Cloth Simulation
• Adaptive Tetrahedral Meshes for Brittle Fracture Simulation
• Strain Based Dynamics
• Coupling 3D Eulerian, Height Field and Particle Methods for the Simulation of Large Scale Liquid Phenomena
• Position-based Elastic Rods
• Optimization Integrator for Large Time Steps
• Stable Orthotropic Materials
• A Peridynamic Perspective on Spring-Mass Fracture
• An Adaptive Virtual Node Algorithm with Robust Mesh Cutting
• Efficient Denting and Bending of Rigid Bodies
• Fast Grid-Based Nonlinear Elasticity for 2D Deformations
• Steklov-Poincare Skinning

 

TVCG Papers appearing at SCA:

• Implicit Incompressible SPH
• Implicit Multibody Penalty-based Distributed Contact
• Large-Scale Liquid Simulation on Adaptive Hexahedral Grids

Here they are thus far:

• Multimaterial Mesh-Based Surface Tracking
• Blending Liquids
• Adaptive Tearing and Cracking of Thin Sheets
• Codimensional Surface Tension Flow on Simplicial Complexes
• Defending Continuous Collision Detection Against Errors
• Physics-Inspired Adaptive Fracture Refinement
• Detailed Water with Coarse Grids: Combining Surface Meshes and  Adaptive Discontinuous Galerkin
• Smoke Rings from Smoke
• Projective Dynamics: Fusing Constraint Projections for Fast Simulation
• Inverse-Foley Animation: Synchronizing rigid-body motions to sound
• Animating Deformable Objects using Sparse Spacetime Constraints 
• Simulating Articulated Subspace Self-Contact
• Robust Hair Capture Using Simulated Examples
• Augmented MPM for Phase-Change and Varied Materials
• Space-Time Editing of Elastic Motion through Material Optimization and Reduction
• Unified Particle Physics for Real-Time Applications
• Active Volumetric Musculoskeletal Systems
• From Capture to Simulation – Connecting Forward and Inverse Problems in Fluids
• Subspace Clothing Simulation Using Adaptive Bases
• Sensitivity-Optimized Rigging for Example-Based Real-Time Clothing Synthesis
• Adaptive Nonlinearity for Collisions in Complex Rod Assemblies
• A Reduced Model for Interactive Hairs

 

TOG:

• Deformation Embedding for Point-Based Elastoplastic Simulation
• Animation of Deformable Bodies with Quadratic Bézier Finite Elements
• Exponential Integrators for Stiff Elastodynamic Problems
• Interactive Generalized Penetration Depth Computation for Rigid and Articulate Models Using Object Norm

Papers:

• Physically-based Human Neck Simulation
• Physically based character skinning
• Tridiagonal Matrix Factorization for Inextensible Hair Strand Simulation
• Parallel Collision Detection in Constant Time
• Connective Tissues Simulation on GPU
• Multi-level Cloth Simulation using GPU Surface Sampling
• Exploring the use of Adaptive Restrained Particles for Graphics Simulations