Real-time content-aware texturing for deformable surfaces

Animation of models often introduces distortions to their parameterisation, as these are typically optimised for a single frame. The net effect is that under deformation, the mapped features, i.e. UV texture maps, bump maps or displacement maps, may appear to stretch or scale in an undesirable way. Ideally, what we would like is for the appearance of such features to remain feasible given any underlying deformation. In this paper we introduce a real-time technique that reduces such distortions based on a distortion control (rigidity) map. In two versions of our proposed technique, the parameter space is warped in either an axis or a non-axis aligned manner based on the minimisation of a non-linear distortion metric. This in turn is solved using a highly optimised hybrid CPU-GPU strategy. The result is real-time dynamic content-aware texturing that reduces distortions in a controlled way. The technique can be applied to reduce distortions in a variety of scenarios, including reusing a low geometric complexity animated sequence with a multitude of detail maps, dynamic procedurally defined features mapped on deformable geometry and animation authoring previews on texture-mapped models. © 2013 ACM

K_{l 3} and \pi_{e 3} transition form factors

$K_{\ell 3}$ and $\pi_{e 3}$ transition form factors are calculated as an application of Dyson-Schwinger equations. The role of nonanalytic contributions to the quark--W-boson vertex is elucidated. A one-parameter model for this vertex provides a uniformly good description of these transitions, including the value of the scalar form factor of the kaon at the Callan-Treiman point. The $K_{\ell 3}$ form factors, $f_\pm^K$, are approximately linear on $t\in [m_e^2,m_\mu^2]$ and have approximately the same slope. $f_-^K(0)$ is a measure of the Euclidean constituent-quark mass ratio: $M^E_s/M^E_u$. In the isospin symmetric limit: $-f_+^\pi(0)= F_\pi(t)$, the electromagnetic pion form factor, and $f_-^\pi(t)\equiv 0$.Comment: 11 pages (incl. 3 figures), elsart.sty, epsf.st

Dissolution geology of organic materials on Saturn’s moon Titan: alien analogs of terrestrial karst

Karst or dissolution geology can occur whenever a circulating fluid can dissolve a geological material. On Earth, the “classical” karst definition is for limestone (CaCO3) in water (H2O), but other material/solvent combinations can create terrestrial dissolution terrain as well. These include so-called “evaporite karst materials” such as halite (NaCl)/H2O or gypsum (CaSO4)/H2O, dolomite (CaMg(CO3)2)/H2O, and even silica (SiO2)/H2O [Ford and Williams, 2007].  On Mars, there has been the suggestion of kieserite (MgSO4)/H2O system that may have formed in an earlier, wetter environment [Baroni and Sgavetta, 2013]. Saturn’s moon Titan extends the definition of karst to include non-aqueous liquids dissolving a landscape made of organic materials. The Cassini mission has provided evidence that Titan’s 1.5 bar nitrogen atmosphrere and cryogenic 94 K surface temperature supports a hydrocarbon-based cycle on Titan similar to the terrestrial water cycle. These circulating liquids may be capable of dissolving some of the surface organic molecules derived from Titan’s complex atmospheric photochemistry. Although under a different gravity, temperature, materials and fluid regime, many of the features on Titan’s surface bear striking resemblances to terrestrial karst terrains. Our investigations have focused on the labyrinth terrains of Titan. These are elevated plateaux of organic materials that appear similar to polygonal karst, tower karst, and fluviokarst on Earth [Malaska et al., 2010; 2017]. Remote sensing data is consistent with these plateaux being constructed of low-dielectric organic materials [Janssen et al. 2009; 2016; Malaska et al, 2016b]. Theoretical calculations followed by cryogenic laboratory experiments have shown that organic materials found on Titan’s surface will dissolve when subjected to Titan’s rainfall of methane-rich fluids [Raulin, 1987; Lorenz and Lunine, 1996; Malaska et al., 2010; 2011; Malaska and Hodyss, 2014; Cornet et al., 2015] and preliminary modelling has been able to reproduce some of the morphologies observed on Titan [Cornet et al., 2017]. Titan’s labyrinth terrains may originate as mixed organic windblown sediments that are later lithified in a process similar to calcite-cemented sandstone on Earth. Organic molecules and sediments produced by Titan’s rich organic photochemistry include organic molecules such as acetylene (C2H2), ethylene (C2H4), hydrogen cyanide (HCN),  benzene (C2H6), acrylonitrile (C2H3CN), acetonitrile (CH3CN), cyanoacetylene (HC2CN), other alkynes and nitriles, and a complex refractory organic materials similar to laboratory tholins. Once uplifted, the saturation equilibrium and kinetics of dissolution for each material and fluid combination affecting the plateau may play key roles in determining how the karstic system will evolve [Malaska et al., 2011; Cornet et al., 2015]. Some of the Titan organic minerals will dissolve, while some will be left behind as an insoluble lag deposit. Advanced laboratory investigations of organic materials on Titan is underway to further understand how these geological structures evolve and compare them with the formation processes of terrestrial analogs. We suggest that karst is a general planetary process wherever circulating fluids are capable of dissolving materials and developing subsurface drainage

The Beagle landing site in Isidis Planitia

The Mars probe Beagle 2 will land in Isidis Planitia. This region satisfies the engineering constraints and has evidence for particularly volatile-rich subsoil. Isidis provides a suitable place for the lander to search for H2O and organic matter

αE-catenin-dependent mechanotransduction is essential for proper convergent extension in zebrafish

Cadherin complexes mediate cell-cell adhesion and are crucial for embryonic development. Besides their structural function, cadherin complexes also transduce tension across the junction-actomyosin axis into proportional biochemical responses. Central to this mechanotransduction is the stretching of the cadherin-F-actin-linker α-catenin, which opens its central domain for binding to effectors such as vinculin. Mechanical unfolding of α-catenin leads to force-dependent reinforcement of cadherin-based junctions as studied in cell culture. The importance of cadherin mechanotransduction for embryonic development has not been studied yet. Here we used TALEN-mediated gene disruption to perturb endogenous αE-catenin in zebrafish development. Zygotic α-catenin mutants fail to maintain their epithelial barrier, resulting in tissue rupturing. We then specifically disrupted mechanotransduction, while maintaining cadherin adhesion, by expressing an αE-catenin construct in which the mechanosensitive domain was perturbed. Expression of either wild-type or mechano-defective α-catenin fully rescues barrier function in α-catenin mutants; however, expression of mechano-defective α-catenin also induces convergence and extension defects. Specifically, the polarization of cadherin-dependent, lamellipodia-driven cell migration of the lateral mesoderm was lost. These results indicate that cadherin mechanotransduction is crucial for proper zebrafish morphogenesis, and uncover one of the essential processes affected by its perturbatio

Eruption of ammonia-water cryomagmas on Titan 1: crystallisation and cooling during ascent

We are developing a semi-analytical model for the ascent of methane-expansion driven ammonia-water cryomagmas on Titan. The range of different crystal fractions resulting from decompression may help to explain the range of apparent rheological properties inferred for surface features

Charge symmetry breaking via rho-omega mixing from model quark-gluon dynamics

The quark-loop contribution to the $\rho^0-\omega$ mixing self-energy function is calculated using a phenomenologically successful QCD-based model field theory in which the $\rho^0$ and $\omega$ mesons are composite $\bar{q}q$ bound states. In this calculation the dressed quark propagator, obtained from a model Dyson-Schwinger equation, is confining. In contrast to previous studies, the meson-$\bar{q}q$ vertex functions are characterised by a strength and range determined by the dynamics of the model; and the calculated off-mass-shell behaviour of the mixing amplitude includes the contribution from the calculated diagonal meson self-energies. The mixing amplitude is shown to be very sensitive to the small isovector component of dynamical chiral symmetry breaking. The spacelike quark-loop mixing-amplitude generates an insignificant charge symmetry breaking nuclear force.Comment: 11 Pages, 3 figures uuencoded and appended to this file, REVTEX 3.0. ANL-PHY-7718-TH-94, KSUCNR-004-94. [!! PostScript file format corrected. Retrieve by anonymous ftp from theory.phy.anl.gov (130.202.20.190), directory pub: mget wpfig*.ps Three files.

Chiral Behaviour of the Rho Meson in Lattice QCD

In order to guide the extrapolation of the mass of the rho meson calculated in lattice QCD with dynamical fermions, we study the contributions to its self-energy which vary most rapidly as the quark mass approaches zero; from the processes $\rho \to \omega \pi$ and $\rho \to \pi \pi$. It turns out that in analysing the most recent data from CP-PACS it is crucial to estimate the self-energy from $\rho \to \pi \pi$ using the same grid of discrete momenta as included implicitly in the lattice simulation. The correction associated with the continuum, infinite volume limit can then be found by calculating the corresponding integrals exactly. Our error analysis suggests that a factor of 10 improvement in statistics at the lowest quark mass for which data currently exists would allow one to determine the physical rho mass to within 5%. Finally, our analysis throws new light on a long-standing problem with the J-parameter.Comment: 13 pages, 7 figures. Full analytic forms of the self-energies are included and a correction in the omega-pi self-energ