Sören Pirk, Till Niese, Torsten Hädrich, Bedrich Benes, Oliver Deussen
We present a novel method for combining developmental tree models with turbulent wind fields. The tree geometry is created from internal growth functions of the developmental model and its response to external stress is induced by a physically-plausible wind field that is simulated by Smoothed Particle Hydrodynamics (SPH). Our tree models are dynamically evolving complex systems that (1) react in real-time to high-frequent changes of the wind simulation; and (2) adapt to long-term wind stress. We extend this process by wind-related effects such as branch breaking as well as bud abrasion and drying. In our interactive system the user can adjust the parameters of the growth model, modify wind properties and resulting forces, and define the tree’s long-term response to wind. By using graphics hardware, our implementation runs at interactive rates for moderately large scenes composed of up to 20 tree models.
Windy Trees: Computing Stress Response for Developmental Tree Models
Rajsekhar Setaluri, Mridul Aanjaneya, Sean Bauer, and Eftychios Sifakis
We introduce a new method for fluid simulation on high-resolution adaptive grids which rivals the throughput and parallelism potential of methods based on uniform grids. Our enabling contribution is SPGrid, a new data structure for compact storage and efficient stream processing of sparsely populated uniform Cartesian grids.SPGrid leverages the extensive hardware acceleration mechanisms inherent in the x86 Virtual Memory Management system to deliver sequential and stencil access bandwidth comparable to dense uniform grids. Second, we eschew tree-based adaptive data structures in favor of storing simulation variables in a pyramid of sparsely populated uniform grids, thus avoiding the cost of indirect memory access associated with pointer-based representations. We show how the costliest algorithmic kernels of fluid simulation can be implemented as a composition of two kernel types: (a) stencil operations on a single sparse uniform grid, and (b) structured data transfers between adjacent levels of resolution, even when modeling non-graded octrees. Finally, we demonstrate an adaptive multigridpreconditioned Conjugate Gradient solver that achieves resolutionindependent convergence rates while admitting a lightweight implementation with a modest memory footprint. Our method is complemented by a new interpolation scheme that reduces dissipative effects and simplifies dynamic grid adaptation. We demonstrate the efficacy of our method in end-to-end simulations of smoke flow.
SPGrid: A Sparse Paged Grid structure applied to adaptive smoke simulation
We present a two-way coupling technique for simulating the complex interaction between hair and fluids. In our approach, the motion of hair and fluids is simulated by evaluating the hydrodynamic forces among them based on boundary handling techniques used in SPH (Smoothed Particle Hydrodynamics) fluids. When hair makes contact with fluids, water absorption inside the hair volume can be simulated with a diffusion process by treating the hair volume as porous media with anisotropic permeability. The saturation of each hair strand is then used to derive the adhesive force between wet hair strands. This enables us to simulate the formation of hair clumps dynamically without the need to employ post clumping processes. The proposed method can be easily applied to any SPH fluid solvers as well as various hair models.
Coupling Hair with Smoothed Particle Hydrodynamics Fluids
Granular materials exhibit a large number of diverse physical phenomena which makes their numerical simulation challenging. When set in motion they flow almost like a fluid, while they can present high shear strength when at rest. Those macroscopic effects result from the material’s microstructure: a particle skeleton with interlocking particles which stick to and slide across each other, producing soil cohesion and friction. For the purpose of Earthmoving equipment operator training, we developed Parallel Particles (P2), a fast and stable position based granular material simulator which models inter-particle friction and adhesion and captures the physical nature of soil to an extend sufficient for training. Our parallel solver makes the approach scalable and applicable to modern multi-core architectures yielding the simulation speed required in this application. Using a regularization procedure, we successfully model visco-elastic particle interactions on the position level which provides real, physical parameters allowing for intuitive tuning. We employ the proposed technique in an Excavator training simulator and demonstrate that it yields physically plausible results at interactive to real-time simulation rates.
Parallel Particles (P^2): A Parallel Position Based Approach for Fast and Stable Simulation of Granular Materials
Mark Browning, Connelly Barnes, Samantha Ritter, Adam Finkelstein
We present a method that combines hand-drawn artwork with fluid simulations to produce animated fluids in the visual style of the artwork. Given a fluid simulation and a set of keyframes rendered by the artist in any medium, our system produces a set of in-betweens that visually matches the style of the keyframes and roughly follows the motion from the underlying simulation. Our method leverages recent advances in patch-based regenerative morphing and image melding to produce temporally coherent sequences with visual fidelity to the target medium. Because direct application of these methods results in motion that is generally not fluid-like, we adapt them to produce motion closely matching that of the underlying simulation. The resulting animation is visually and temporally coherent, stylistically consistent with the given keyframes, and approximately matches the motion from the simulation. We demonstrate the method with animations in a variety of visual styles.
Stylized Keyframe Animation of Fluid Simulations
The SIGGRAPH Asia 2014 collection includes:
Transactions on Graphics, to be presented at SIG Asia:
Xinxin Zhang, Robert Bridson
Solving the N-body problem, i.e. the Poisson problem with point sources, is a common task in graphics and simulation. The naive direct summation of the kernel function over all particles scales quadratically, rendering it too slow for large problems, while the optimal Fast Multipole Method has drastic implementation complexity and can sometimes carry too high an overhead to be practical. We present a new Particle-Particle Particle-Mesh (PPPM) algorithm which is fast, accurate, and easy to implement even in parallel on a GPU. We capture long-range interactions with a fast multigrid solver on a background grid with a novel boundary condition, while short-range interactions are calculated directly with a new error compensation to avoid error from the background grid. We demonstrate the power of PPPM with a new vortex particle smoke solver, which features a vortex segment-approach to the stretching term, potential flow to enforce no-stick solid boundaries on arbitrary moving solid boundaries, and a new mechanism for vortex shedding from boundary layers. Comparison against a simpler Vortex-in-Cell approach shows PPPM can produce significantly more detailed results with less computation. In addition, we use our PPPM solver for a Poisson surface reconstruction problem to show its potential as a general-purpose Poisson solver.
Particle-particle Particle-mesh (PPPM) Fast Summation for Fluids and Beyond
Adam W. Bargteil, Elaine Cohen
In this paper, we investigate the use of quadratic finite elements for graphical animation of deformable bodies. We consider both integrating quadratic elements with conventional linear elements to achieve a computationally efficient adaptive-degree simulation framework as well as wholly quadratic elements for the simulation of non-linear rest shapes. In both cases, we adopt the Bézier basis functions and employ a co-rotational linear strain formulation. As with linear elements, the co-rotational formulation allows us to precompute per-element stiffness matrices, resulting in substantial computational savings. We present several examples that demonstrate the advantages of quadratic elements in general and our adaptive-degree system in particular. Furthermore, we demonstrate, for the first time in computer graphics, animations of volumetric deformable bodies with non-linear rest shapes.
Animation of Deformable Bodies with Quadratic Bezier Finite Elements
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!
Hongyi Xu, Jernej Barbic
We present an algorithm for fast continuous collision detection between points and signed distance fields. Such robust queries are often needed in computer animation, haptics and virtual reality applications, but have so far only been investigated for polygon (triangular) geometry representations. We demonstrate how to use an octree subdivision of the distance field for fast traversal of distance field cells. We also give a method to combine octree subdivision with points organized into a tree hierarchy, for efficient culling of continuous collision detection tests. We apply our method to multibody rigid simulations, and demonstrate that our method accelerates continuous collision detection between points and distance fields by an order of magnitude.
Continuous Collision Detection Between Points and Signed Distance Fields