2,784 research outputs found
Visual Importance-Biased Image Synthesis Animation
Present ray tracing algorithms are computationally intensive, requiring hours of computing time for complex scenes. Our previous work has dealt with the development of an overall approach to the application of visual attention to progressive and adaptive ray-tracing techniques. The approach facilitates large computational savings by modulating the supersampling rates in an image by the visual importance of the region being rendered. This paper extends the approach by incorporating temporal changes into the models and techniques developed, as it is expected that further efficiency savings can be reaped for animated scenes. Applications for this approach include entertainment, visualisation and simulation
Source coding for transmission of reconstructed dynamic geometry: a rate-distortion-complexity analysis of different approaches
Live 3D reconstruction of a human as a 3D mesh with commodity electronics is becoming a reality. Immersive applications (i.e. cloud gaming, tele-presence) benefit from effective transmission of such content over a bandwidth limited link. In this paper we outline different approaches for compressing live reconstructed mesh geometry based on distributing mesh reconstruction functions between sender and receiver. We evaluate rate-performance-complexity of different configurations. First, we investigate 3D mesh compression methods (i.e. dynamic/static) from MPEG-4. Second, we evaluate the option of using octree based point cloud compression and receiver side surface reconstruction
Shape Animation with Combined Captured and Simulated Dynamics
We present a novel volumetric animation generation framework to create new
types of animations from raw 3D surface or point cloud sequence of captured
real performances. The framework considers as input time incoherent 3D
observations of a moving shape, and is thus particularly suitable for the
output of performance capture platforms. In our system, a suitable virtual
representation of the actor is built from real captures that allows seamless
combination and simulation with virtual external forces and objects, in which
the original captured actor can be reshaped, disassembled or reassembled from
user-specified virtual physics. Instead of using the dominant surface-based
geometric representation of the capture, which is less suitable for volumetric
effects, our pipeline exploits Centroidal Voronoi tessellation decompositions
as unified volumetric representation of the real captured actor, which we show
can be used seamlessly as a building block for all processing stages, from
capture and tracking to virtual physic simulation. The representation makes no
human specific assumption and can be used to capture and re-simulate the actor
with props or other moving scenery elements. We demonstrate the potential of
this pipeline for virtual reanimation of a real captured event with various
unprecedented volumetric visual effects, such as volumetric distortion,
erosion, morphing, gravity pull, or collisions
Simulating Electron Transport and Synchrotron Emission in Radio Galaxies: Shock Acceleration and Synchrotron Aging in Three-Dimensional Flows
We present the first three-dimensional MHD radio galaxy simulations that
explicitly model transport of relativistic electrons, including diffusive
acceleration at shocks as well as radiative and adiabatic cooling in smooth
flows. We discuss three simulations of light Mach 8 jets, designed to explore
the effects of shock acceleration and radiative aging on the nonthermal
particle populations that give rise to synchrotron and inverse-Compton
radiations. We also conduct detailed synthetic radio observations of our
simulated objects. We have gained several key insights from this approach: 1.
The jet head in these multidimensional simulations is extremely complex. The
classical jet termination shock is often absent, but motions of the jet
terminus spin a ``shock-web complex'' within the backflowing jet material of
the head. 2. Understanding the spectral distribution of energetic electrons in
these simulations relies partly upon understanding the shock-web complex, for
it can give rise to distributions that confound interpretation in terms of the
standard model for radiative aging of radio galaxies. 3. The magnetic field
outside of the jet itself becomes very intermittent and filamentary in these
simulations, yet adiabatic expansion causes most of the cocoon volume to be
occupied by field strengths considerably diminished below the nominal jet
value. Thus population aging rates vary considerably from point to point.Comment: 44 pages, 6 figures; to be published in the Astrophysical Journal
(August 2001); higher-quality figures can be found at
http://www.msi.umn.edu/Projects/twj/radjet/radjet.htm
Mechanical properties of mesoporous ceria nanoarchitectures
Architectural constructs are engineered to impart desirable mechanical properties facilitating bridges spanning a thousand meters and buildings nearly 1 km in height. However, do the same 'engineering-rules' translate to the nanoscale, where the architectural features are less than 0.0001 mm in size? Here, we calculate the mechanical properties of a porous ceramic functional material, ceria, as a function of its nanoarchitecture using molecular dynamics simulation and predict its yield strength to be almost two orders of magnitude higher than the parent bulk material. In particular, we generate models of nanoporous ceria with either a hexagonal or cubic array of one-dimensional pores and simulate their responses to mechanical load. We find that the mechanical properties are critically dependent upon the orientation between the crystal structure (symmetry, direction) and the pore structure (symmetry, direction). This journal i
Three-Dimensional Simulations of Bi-Directed Magnetohydrodynamic Jets Interacting with Cluster Environments
We report on a series of three-dimensional magnetohydrodynamic simulations of
active galactic nucleus (AGN) jet propagation in realistic models of magnetized
galaxy clusters. We are primarily interested in the details of energy transfer
between jets and the intracluster medium (ICM) to help clarify what role such
flows could have in the reheating of cluster cores. Our simulated jets feature
a range of intermittency behaviors, including intermittent jets that
periodically switch on and off and one model jet that shuts down completely,
naturally creating a relic plume. The ICM into which these jets propagate
incorporates tangled magnetic field geometries and density substructure
designed to mimic some likely features of real galaxy clusters. We find that
our jets are characteristically at least 60% efficient at transferring thermal
energy to the ICM. Irreversible heat energy is not uniformly distributed,
however, instead residing preferentially in regions very near the jet/cocoon
boundaries. While intermittency affects the details of how, when, and where
this energy is deposited, all of our models generically fail to heat the
cluster cores uniformly. Both the detailed density structure and nominally weak
magnetic fields in the ICM play interesting roles in perturbing the flows,
particularly when the jets are non-steady. Still, this perturbation is never
sufficient to isotropize the jet energy deposition, suggesting that some other
ingredient is required for AGN jets to successfully reheat cluster cores.Comment: 19 pages, 18 figures, Accepted for publication in the Astrophysical
Journa
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