TY - CONF
AB - We present an approach for artist-directed animation of liquids using multiple levels of control over the simulation, ranging from the overall tracking of desired shapes to highly detailed secondary effects such as dripping streams, separating sheets of fluid, surface waves and ripples. The first portion of our technique is a volume preserving morph that allows the animator to produce a plausible fluid-like motion from a sparse set of control meshes. By rasterizing the resulting control meshes onto the simulation grid, the mesh velocities act as boundary conditions during the projection step of the fluid simulation. We can then blend this motion together with uncontrolled fluid velocities to achieve a more relaxed control over the fluid that captures natural inertial effects. Our method can produce highly detailed liquid surfaces with control over sub-grid details by using a mesh-based surface tracker on top of a coarse grid-based fluid simulation. We can create ripples and waves on the fluid surface attracting the surface mesh to the control mesh with spring-like forces and also by running a wave simulation over the surface mesh. Our video results demonstrate how our control scheme can be used to create animated characters and shapes that are made of water.
AU - Raveendran, Karthik
AU - Thuerey, Nils
AU - Wojtan, Christopher J
AU - Turk, Greg
ID - 3119
T2 - Proceedings of the ACM SIGGRAPH/Eurographics Symposium on Computer Animation
TI - Controlling liquids using meshes
ER -
TY - JOUR
AB - We introduce a strategy based on Kustin-Miller unprojection that allows us to construct many hundreds of Gorenstein codimension 4 ideals with 9 × 16 resolutions (that is, nine equations and sixteen first syzygies). Our two basic games are called Tom and Jerry; the main application is the biregular construction of most of the anticanonically polarised Mori Fano 3-folds of Altinok's thesis. There are 115 cases whose numerical data (in effect, the Hilbert series) allow a Type I projection. In every case, at least one Tom and one Jerry construction works, providing at least two deformation families of quasismooth Fano 3-folds having the same numerics but different topology. © 2012 Copyright Foundation Compositio Mathematica.
AU - Brown, Gavin
AU - Kerber, Michael
AU - Reid, Miles
ID - 3120
IS - 4
JF - Compositio Mathematica
TI - Fano 3 folds in codimension 4 Tom and Jerry Part I
VL - 148
ER -
TY - JOUR
AB - Voltage-activated Ca(2+) channels (VACCs) mediate Ca(2+) influx to trigger action potential-evoked neurotransmitter release, but the mechanism by which Ca(2+) regulates spontaneous transmission is unclear. We found that VACCs are the major physiological triggers for spontaneous release at mouse neocortical inhibitory synapses. Moreover, despite the absence of a synchronizing action potential, we found that spontaneous fusion of a GABA-containing vesicle required the activation of multiple tightly coupled VACCs of variable type.
AU - Williams, Courtney
AU - Chen, Wenyan
AU - Lee, Chia
AU - Yaeger, Daniel
AU - Vyleta, Nicholas
AU - Smith, Stephen
ID - 3121
IS - 9
JF - Nature Neuroscience
TI - Coactivation of multiple tightly coupled calcium channels triggers spontaneous release of GABA
VL - 15
ER -
TY - JOUR
AB - Since Darwin's pioneering research on plant reproductive biology (e.g. Darwin 1877), understanding the mechanisms maintaining the diverse sexual strategies of plants has remained an important challenge for evolutionary biologists. In some species, populations are sexually polymorphic and contain two or more mating morphs (sex phenotypes). Differences in morphology or phenology among the morphs influence patterns of non-random mating. In these populations, negative frequency-dependent selection arising from disassortative (intermorph) mating is usually required for the evolutionary maintenance of sexual polymorphism, but few studies have demonstrated the required patterns of non-random mating. In the current issue of Molecular Ecology, Shang (2012) make an important contribution to our understanding of how disassortative mating influences sex phenotype ratios in Acer pictum subsp. mono (painted maple), a heterodichogamous, deciduous tree of eastern China. They monitored sex expression in 97 adults and used paternity analysis of open-pollinated seed to examine disassortative mating among three sex phenotypes. Using a deterministic 'pollen transfer' model, Shang et al. present convincing evidence that differences in the degree of disassortative mating in progeny arrays of the sex phenotypes can explain their uneven frequencies in the adult population. This study provides a useful example of how the deployment of genetic markers, demographic monitoring and modelling can be integrated to investigate the maintenance of sexual diversity in plants.
AU - Field, David
AU - Barrett, Spencer
ID - 3122
IS - 15
JF - Molecular Ecology
TI - Disassortative mating and the maintenance of sexual polymorphism in painted maple
VL - 21
ER -
TY - CONF
AB - We introduce the idea of using an explicit triangle mesh to track the air/fluid interface in a smoothed particle hydrodynamics (SPH) simulator. Once an initial surface mesh is created, this mesh is carried forward in time using nearby particle velocities to advect the mesh vertices. The mesh connectivity remains mostly unchanged across time-steps; it is only modified locally for topology change events or for the improvement of triangle quality. In order to ensure that the surface mesh does not diverge from the underlying particle simulation, we periodically project the mesh surface onto an implicit surface defined by the physics simulation. The mesh surface gives us several advantages over previous SPH surface tracking techniques. We demonstrate a new method for surface tension calculations that clearly outperforms the state of the art in SPH surface tension for computer graphics. We also demonstrate a method for tracking detailed surface information (like colors) that is less susceptible to numerical diffusion than competing techniques. Finally, our temporally-coherent surface mesh allows us to simulate high-resolution surface wave dynamics without being limited by the particle resolution of the SPH simulation.
AU - Yu, Jihun
AU - Wojtan, Christopher J
AU - Turk, Greg
AU - Yap, Chee
ID - 3123
IS - 2
T2 - Computer Graphics Forum
TI - Explicit mesh surfaces for particle based fluids
VL - 31
ER -
TY - CONF
AB - We consider the problem of inference in a graphical model with binary variables. While in theory it is arguably preferable to compute marginal probabilities, in practice researchers often use MAP inference due to the availability of efficient discrete optimization algorithms. We bridge the gap between the two approaches by introducing the Discrete Marginals technique in which approximate marginals are obtained by minimizing an objective function with unary and pairwise terms over a discretized domain. This allows the use of techniques originally developed for MAP-MRF inference and learning. We explore two ways to set up the objective function - by discretizing the Bethe free energy and by learning it from training data. Experimental results show that for certain types of graphs a learned function can outperform the Bethe approximation. We also establish a link between the Bethe free energy and submodular functions.
AU - Korc, Filip
AU - Kolmogorov, Vladimir
AU - Lampert, Christoph
ID - 3124
TI - Approximating marginals using discrete energy minimization
ER -
TY - CONF
AB - We propose a new learning method to infer a mid-level feature representation that combines the advantage of semantic attribute representations with the higher expressive power of non-semantic features. The idea lies in augmenting an existing attribute-based representation with additional dimensions for which an autoencoder model is coupled with a large-margin principle. This construction allows a smooth transition between the zero-shot regime with no training example, the unsupervised regime with training examples but without class labels, and the supervised regime with training examples and with class labels. The resulting optimization problem can be solved efficiently, because several of the necessity steps have closed-form solutions. Through extensive experiments we show that the augmented representation achieves better results in terms of object categorization accuracy than the semantic representation alone.
AU - Sharmanska, Viktoriia
AU - Quadrianto, Novi
AU - Lampert, Christoph
ID - 3125
IS - PART 5
TI - Augmented attribute representations
VL - 7576
ER -
TY - CONF
AB - In this work we propose a new information-theoretic clustering algorithm that infers cluster memberships by direct optimization of a non-parametric mutual information estimate between data distribution and cluster assignment. Although the optimization objective has a solid theoretical foundation it is hard to optimize. We propose an approximate optimization formulation that leads to an efficient algorithm with low runtime complexity. The algorithm has a single free parameter, the number of clusters to find. We demonstrate superior performance on several synthetic and real datasets.
AU - Müller, Andreas
AU - Nowozin, Sebastian
AU - Lampert, Christoph
ID - 3126
TI - Information theoretic clustering using minimal spanning trees
VL - 7476
ER -
TY - CONF
AB - When searching for characteristic subpatterns in potentially noisy graph data, it appears self-evident that having multiple observations would be better than having just one. However, it turns out that the inconsistencies introduced when different graph instances have different edge sets pose a serious challenge. In this work we address this challenge for the problem of finding maximum weighted cliques.
We introduce the concept of most persistent soft-clique. This is subset of vertices, that 1) is almost fully or at least densely connected, 2) occurs in all or almost all graph instances, and 3) has the maximum weight. We present a measure of clique-ness, that essentially counts the number of edge missing to make a subset of vertices into a clique. With this measure, we show that the problem of finding the most persistent soft-clique problem can be cast either as: a) a max-min two person game optimization problem, or b) a min-min soft margin optimization problem. Both formulations lead to the same solution when using a partial Lagrangian method to solve the optimization problems. By experiments on synthetic data and on real social network data, we show that the proposed method is able to reliably find soft cliques in graph data, even if that is distorted by random noise or unreliable observations.
AU - Quadrianto, Novi
AU - Lampert, Christoph
AU - Chen, Chao
ID - 3127
T2 - Proceedings of the 29th International Conference on Machine Learning
TI - The most persistent soft-clique in a set of sampled graphs
ER -
TY - JOUR
AB - We consider two-player zero-sum stochastic games on graphs with ω-regular winning conditions specified as parity objectives. These games have applications in the design and control of reactive systems. We survey the complexity results for the problem of deciding the winner in such games, and in classes of interest obtained as special cases, based on the information and the power of randomization available to the players, on the class of objectives and on the winning mode. On the basis of information, these games can be classified as follows: (a) partial-observation (both players have partial view of the game); (b) one-sided partial-observation (one player has partial-observation and the other player has complete-observation); and (c) complete-observation (both players have complete view of the game). The one-sided partial-observation games have two important subclasses: the one-player games, known as partial-observation Markov decision processes (POMDPs), and the blind one-player games, known as probabilistic automata. On the basis of randomization, (a) the players may not be allowed to use randomization (pure strategies), or (b) they may choose a probability distribution over actions but the actual random choice is external and not visible to the player (actions invisible), or (c) they may use full randomization. Finally, various classes of games are obtained by restricting the parity objective to a reachability, safety, Büchi, or coBüchi condition. We also consider several winning modes, such as sure-winning (i.e., all outcomes of a strategy have to satisfy the winning condition), almost-sure winning (i.e., winning with probability 1), limit-sure winning (i.e., winning with probability arbitrarily close to 1), and value-threshold winning (i.e., winning with probability at least ν, where ν is a given rational).
AU - Chatterjee, Krishnendu
AU - Doyen, Laurent
AU - Henzinger, Thomas A
ID - 3128
IS - 2
JF - Formal Methods in System Design
TI - A survey of partial-observation stochastic parity games
VL - 43
ER -