36,177 research outputs found
Path-tracing Monte Carlo Library for 3D Radiative Transfer in Highly Resolved Cloudy Atmospheres
Interactions between clouds and radiation are at the root of many
difficulties in numerically predicting future weather and climate and in
retrieving the state of the atmosphere from remote sensing observations. The
large range of issues related to these interactions, and in particular to
three-dimensional interactions, motivated the development of accurate radiative
tools able to compute all types of radiative metrics, from monochromatic, local
and directional observables, to integrated energetic quantities. In the
continuity of this community effort, we propose here an open-source library for
general use in Monte Carlo algorithms. This library is devoted to the
acceleration of path-tracing in complex data, typically high-resolution
large-domain grounds and clouds. The main algorithmic advances embedded in the
library are those related to the construction and traversal of hierarchical
grids accelerating the tracing of paths through heterogeneous fields in
null-collision (maximum cross-section) algorithms. We show that with these
hierarchical grids, the computing time is only weakly sensitivive to the
refinement of the volumetric data. The library is tested with a rendering
algorithm that produces synthetic images of cloud radiances. Two other examples
are given as illustrations, that are respectively used to analyse the
transmission of solar radiation under a cloud together with its sensitivity to
an optical parameter, and to assess a parametrization of 3D radiative effects
of clouds.Comment: Submitted to JAMES, revised and submitted again (this is v2
A fast GPU Monte Carlo Radiative Heat Transfer Implementation for Coupling with Direct Numerical Simulation
We implemented a fast Reciprocal Monte Carlo algorithm, to accurately solve
radiative heat transfer in turbulent flows of non-grey participating media that
can be coupled to fully resolved turbulent flows, namely to Direct Numerical
Simulation (DNS). The spectrally varying absorption coefficient is treated in a
narrow-band fashion with a correlated-k distribution. The implementation is
verified with analytical solutions and validated with results from literature
and line-by-line Monte Carlo computations. The method is implemented on GPU
with a thorough attention to memory transfer and computational efficiency. The
bottlenecks that dominate the computational expenses are addressed and several
techniques are proposed to optimize the GPU execution. By implementing the
proposed algorithmic accelerations, a speed-up of up to 3 orders of magnitude
can be achieved, while maintaining the same accuracy
VolumeEVM: A new surface/volume integrated model
Volume visualization is a very active research area in the field of scien-tific
visualization. The Extreme Vertices Model (EVM) has proven to be
a complete intermediate model to visualize and manipulate volume data
using a surface rendering approach. However, the ability to integrate the
advantages of surface rendering approach with the superiority in visual exploration
of the volume rendering would actually produce a very complete
visualization and edition system for volume data. Therefore, we decided
to define an enhanced EVM-based model which incorporates the volumetric
information required to achieved a nearly direct volume visualization
technique. Thus, VolumeEVM was designed maintaining the same EVM-based
data structure plus a sorted list of density values corresponding to
the EVM-based VoIs interior voxels. A function which relates interior
voxels of the EVM with the set of densities was mandatory to be defined.
This report presents the definition of this new surface/volume integrated
model based on the well known EVM encoding and propose implementations
of the main software-based direct volume rendering techniques
through the proposed model.Postprint (published version
- …