Physics-Animation Forum?

I was recently asked whether there exists any internet forum dedicated to physics-based animation. The two that came to mind are Gamedev’s Math & Physics forum and Bullet’s physics simulation forums (both linked in the right column of the page), though my impression is that these naturally tend to be focused towards games, and with somewhat greater emphasis on rigid bodies and collision detection. So I wanted to pose some questions to you…

  1. Are there other forum sites that focus on physical simulation for computer graphics? If so please post a link in the comments.
  2. Would a dedicated physics-based animation forum be of genuine use to you? (Alternatively, do existing forums already serve this purpose, or do you not see a need for such a forum?)

Feel free to share any other thoughts you have on the subject.

Iso-geometric Analysis Based on Catmull-Clark Subdivision Solids

We present a volumetric iso-geometric finite element analysis based on Catmull-Clark solids. This concept allows one to use the same representation for the modeling, the physical simulation, and the visualization, which optimizes the design process and narrows the gap between CAD and CAE. In our method the boundary of the solid model is a Catmull-Clark surface with optional corners and creases to support the modeling phase. The crucial point in the simulation phase is the need to perform efficient  integration for the elements. We propose a method similar to the standard subdivision surface evaluation technique, such that numerical quadrature can be used.
Experiments show that our approach converges faster than methods based on tri-linear and tri-quadratic elements. However, the topological structure of Catmull-Clark elements is as simple as the structure of linear elements. Furthermore, the Catmull-Clark elements we use are C2-continuous on the boundary and in the interior except for irregular vertices and edges.

Iso-geometric Analysis Based on Catmull-Clark Subdivision Solids

Fast and Scalable CPU/GPU Collision Detection for Rigid and Deformable Surfaces

We present a new hybrid CPU/GPU collision detection technique for rigid and deformable objects based on spatial subdivision. Our approach efficiently exploits the massive computational capabilities of modern CPUs and GPUs commonly found in off-the-shelf computer systems. The algorithm is specifically tailored to be highly scalable on both the CPU and the GPU sides. We can compute discrete and continuous external and self-collisions of non-penetrating rigid and deformable objects consisting of many tens of thousands of triangles in few milliseconds on a modern PC. Our approach is orders of magnitude faster than earlier CPU-based approaches and up to twice as fast as the most recent GPU-based techniques.

Fast and Scalable CPU/GPU Collision Detection for Rigid and Deformable Surfaces

Hybrid Simulation of Miscible Mixing with Viscous Fingering

By modeling mass transfer phenomena, we simulate solids and liquids dissolving or changing to other substances.We also deal with the very small-scale phenomena that occur when a fluid spreads out at the interface of another fluid. We model the pressure at the interfaces between fluids with Darcy’s Law and represent the viscous fingering phenomenon in which a fluid interface spreads out with a fractal-like shape. We use hybrid grid-based simulation and smoothed particle hydrodynamics (SPH) to simulate intermolecular diffusion and attraction using particles at a computable scale. We have produced animations showing fluids mixing and objects dissolving.

Hybrid Simulation of Miscible Mixing with Viscous Fingering

Fast Particle-Based Visual Simulation of Melting Ice

The visual simulation of natural phenomena has been widely studied. Although several methods have been proposed to simulate melting, the flows of meltwater drops on the surfaces of objects are not taken into account. In this paper, we propose a particle-based method for the simulation of the melting and freezing of ice objects and the interactions between ice and fluids. To simulate the flow of meltwater on ice and the formation of water droplets, a simple interfacial tension is proposed, which can be easily incorporated into common particle-based simulation methods such as Smoothed Particle Hydrodynamics. The computations of heat transfer, the phase transition between ice and water, the interactions between ice and fluids, and the separation of ice due to melting are further accelerated by implementing our method using CUDA. We demonstrate our simulation and rendering method for depicting melting ice at interactive frame-rates.

Fast Particle-Based Visual Simulation of Melting Ice

Interactive SPH Simulation and Rendering on the GPU

In this paper we introduce a novel parallel and interactive SPH simulation and rendering method on the GPU using CUDA which allows for high quality visualization. The crucial particle neighborhood search is based onZ-indexing and parallel sorting which eliminates GPU memory overhead due to grid or hierarchical data structures. Furthermore, it overcomes limitations imposed by shading languages allowing it to be very flexible and approaching the practical limits of modern graphics hardware. For visualizing the SPH simulation we introduce a new rendering pipeline. In the first step, all surface particles are efficiently extracted from the SPH particle cloud exploiting the simulation data. Subsequently, a partial and therefore fast distance field volume is rasterized from the surface particles. In the last step, the distance field volume is directly rendered using state-of-the-art GPU raycasting. This rendering pipeline allows for high quality visualization at very high frame rates.

Interactive SPH Simulation and Rendering on the GPU

Vector Fluid: A Vector Graphics Depiction of Free Surface Flow

We present a simple technique for creating fluid silhouettes described with vector graphics, which we call “Vector Fluid.” In our system, a solid region in the fluid is represented as a closed contour and advected by fluid flow to form a curly and clear shape similar to marbling or sumi-nagashi. The fundamental principle behind our method is that contours of solid regions should not collide. This means that if the initial shape of the region is a concave polygon, that shape should maintain its topology so that it can be rendered as a regular concave polygon, no matter how irregularly the contour is distorted by advection. In contrast to other techniques, our approach explicitly neglects topology changes to track surfaces in a trade off of computational cost and complexity. We also introduce an adaptive contour sampling technique to reduce this extra cost. We explore specific examples in 2D for art oriented usage and show applications and robustness of our method to exhibit organic fluid components. We also demonstrate how to port our entire algorithm onto a GPU to boost interactive performance for complex scenes.

Vector Fluid: A Vector Graphics Depiction of Free Surface Flow

Piles of Objects

We present a method for directly modeling piles of objects in multibody simulations. Piles of objects represent some of the more interesting, but also most time-consuming portion of simulation. We propose a method for reducing computation in many of these situations by explicitly modeling the piles that the objects may form into. By modeling pile behavior rather than the behavior of all individual objects, we can achieve realistic results in less time, and without directly modeling the frictional component that leads to desired pile shapes. Our method is simple to implement and can be easily integrated with existing rigid body simulations. We observe notable speedups in several rigid body examples, and generate a wider variety of piled structures than possible with strict impulse-based simulation.

Piles of Objects