68,094 research outputs found
Massively Parallel Ray Tracing Algorithm Using GPU
Ray tracing is a technique for generating an image by tracing the path of
light through pixels in an image plane and simulating the effects of
high-quality global illumination at a heavy computational cost. Because of the
high computation complexity, it can't reach the requirement of real-time
rendering. The emergence of many-core architectures, makes it possible to
reduce significantly the running time of ray tracing algorithm by employing the
powerful ability of floating point computation. In this paper, a new GPU
implementation and optimization of the ray tracing to accelerate the rendering
process is presented
The Iray Light Transport Simulation and Rendering System
While ray tracing has become increasingly common and path tracing is well
understood by now, a major challenge lies in crafting an easy-to-use and
efficient system implementing these technologies. Following a purely
physically-based paradigm while still allowing for artistic workflows, the Iray
light transport simulation and rendering system allows for rendering complex
scenes by the push of a button and thus makes accurate light transport
simulation widely available. In this document we discuss the challenges and
implementation choices that follow from our primary design decisions,
demonstrating that such a rendering system can be made a practical, scalable,
and efficient real-world application that has been adopted by various companies
across many fields and is in use by many industry professionals today
Modelling light scattering by absorbing smooth and slightly rough facetted particles
A method for approximating light scattering properties of strongly absorbing facetted particles which are large compared to the wavelength is presented. It consists in adding the approximated external diffraction and reflection far fields and is demonstrated for a smooth hexagonal prism. This computationally fast method is extended towards prisms with slightly rough surfaces by introducing a surface scaling factor in order to account for edge effects on subfacets forming the rough surface. These effects become more pronounced with decreasing subfacet dimension to wavelength ratio. Azimuthally resolved light scattering patterns, phase functions and degree of linear polarisation obtained by this method and by the Discrete Dipole Approximation are compared for hexagonal prisms with smooth and slightly rough surfaces, respectively.Peer reviewedSubmitted Versio
A public code for general relativistic, polarised radiative transfer around spinning black holes
Ray tracing radiative transfer is a powerful method for comparing theoretical
models of black hole accretion flows and jets with observations. We present a
public code, grtrans, for carrying out such calculations in the Kerr metric,
including the full treatment of polarised radiative transfer and parallel
transport along geodesics. The code is written in Fortran 90 and efficiently
parallelises with OpenMP, and the full code and several components have Python
interfaces. We describe several tests which are used for verifiying the code,
and we compare the results for polarised thin accretion disc and semi-analytic
jet problems with those from the literature as examples of its use. Along the
way, we provide accurate fitting functions for polarised synchrotron emission
and transfer coefficients from thermal and power law distribution functions,
and compare results from numerical integration and quadrature solutions of the
polarised radiative transfer equations. We also show that all transfer
coefficients can play an important role in predicted images and polarisation
maps of the Galactic center black hole, Sgr A*, at submillimetre wavelengths.Comment: 22 pages, 12 figures, submitted to MNRAS. code available at:
github.com/jadexter/grtran
Fast and accurate frequency-dependent radiation transport for hydrodynamics simulations in massive star formation
Context: Radiative feedback plays a crucial role in the formation of massive
stars. The implementation of a fast and accurate description of the proceeding
thermodynamics in pre-stellar cores and evolving accretion disks is therefore a
main effort in current hydrodynamics simulations.
Aims: We introduce our newly implemented three-dimensional frequency
dependent radiation transport algorithm for hydrodynamics simulations of
spatial configurations with a dominant central source.
Methods: The module combines the advantage of the speed of an approximate
Flux Limited Diffusion (FLD) solver with the high accuracy of a frequency
dependent first order ray-tracing routine.
Results: We prove the viability of the scheme in a standard radiation
benchmark test compared to a full frequency dependent Monte-Carlo based
radiative transfer code. The setup includes a central star, a circumstellar
flared disk, as well as an envelope. The test is performed for different
optical depths. Considering the frequency dependence of the stellar
irradiation, the temperature distributions can be described precisely in the
optically thin, thick, and irradiated transition regions. Resulting radiative
forces onto dust grains are reproduced with high accuracy. The achievable
parallel speedup of the method imposes no restriction on further radiative
(magneto-) hydrodynamics simulations.
Conclusions: The proposed approximate radiation transport method enables
frequency dependent radiation hydrodynamics studies of the evolution of
pre-stellar cores and circumstellar accretion disks around an evolving massive
star in a highly efficient and accurate manner.Comment: 16 pages, 11 figure
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