1,357 research outputs found
Ray Tracing Structured AMR Data Using ExaBricks
Structured Adaptive Mesh Refinement (Structured AMR) enables simulations to
adapt the domain resolution to save computation and storage, and has become one
of the dominant data representations used by scientific simulations; however,
efficiently rendering such data remains a challenge. We present an efficient
approach for volume- and iso-surface ray tracing of Structured AMR data on
GPU-equipped workstations, using a combination of two different data
structures. Together, these data structures allow a ray tracing based renderer
to quickly determine which segments along the ray need to be integrated and at
what frequency, while also providing quick access to all data values required
for a smooth sample reconstruction kernel. Our method makes use of the RTX ray
tracing hardware for surface rendering, ray marching, space skipping, and
adaptive sampling; and allows for interactive changes to the transfer function
and implicit iso-surfacing thresholds. We demonstrate that our method achieves
high performance with little memory overhead, enabling interactive high quality
rendering of complex AMR data sets on individual GPU workstations
Beyond ExaBricks: GPU Volume Path Tracing of AMR Data
Adaptive Mesh Refinement (AMR) is becoming a prevalent data representation
for scientific visualization. Resulting from large fluid mechanics simulations,
the data is usually cell centric, imposing a number of challenges for high
quality reconstruction at sample positions. While recent work has concentrated
on real-time volume and isosurface rendering on GPUs, the rendering methods
used still focus on simple lighting models without scattering events and global
illumination. As in other areas of rendering, key to real-time performance are
acceleration data structures; in this work we analyze the major bottlenecks of
data structures that were originally optimized for camera/primary ray traversal
when used with the incoherent ray tracing workload of a volumetric path tracer,
and propose strategies to overcome the challenges coming with this
A fast tree-based method for estimating column densities in adaptive mesh refinement codes: Influence of UV radiation field on the structure of molecular clouds
International audienceContext. Ultraviolet radiation plays a crucial role in molecular clouds. Radiation and matter are tightly coupled and their interplay influences the physical and chemical properties of gas. In particular, modeling the radiation propagation requires calculating column densities, which can be numerically expensive in high-resolution multidimensional simulations. Aims. Developing fast methods for estimating column densities is mandatory if we are interested in the dynamical influence of the radiative transfer. In particular, we focus on the effect of the UV screening on the dynamics and on the statistical properties of molecular clouds.Methods. We have developed a tree-based method for a fast estimate of column densities, implemented in the adaptive mesh refinement code RAMSES. We performed numerical simulations using this method in order to analyze the influence of the screening on the clump formation.Results. We find that the accuracy for the extinction of the tree-based method is better than 10%, while the relative error for the column density can be much more. We describe the implementation of a method based on precalculating the geometrical terms that noticeably reduces the calculation time. To study the influence of the screening on the statistical properties of molecular clouds we present the probability distribution function of gas and the associated temperature per density bin and the mass spectra for different density thresholds.Conclusions. The tree-based method is fast and accurate enough to be used during numerical simulations since no communication is needed between CPUs when using a fully threaded tree. It is then suitable to parallel computing. We show that the screening for far UV radiation mainly affects the dense gas, thereby favoring low temperatures and affecting the fragmentation. We show that when we include the screening, more structures are formed with higher densities in comparison to the case that does not include this effect. We interpret this as the result of the shielding effect of dust, which protects the interiors of clumps from the incoming radiation, thus diminishing the temperature and changing locally the Jeans mass
Simulations of recoiling black holes: adaptive mesh refinement and radiative transfer
(Abridged) We here continue our effort to model the behaviour of matter when
orbiting or accreting onto a generic black hole by developing a new numerical
code employing advanced techniques geared solve the equations of in
general-relativistic hydrodynamics. The new code employs a number of
high-resolution shock-capturing Riemann-solvers and reconstruction algorithms,
exploiting the enhanced accuracy and the reduced computational cost of AMR
techniques. In addition, the code makes use of sophisticated ray-tracing
libraries that, coupled with general-relativistic radiation-transfer
calculations, allow us to compute accurately the electromagnetic emissions from
such accretion flows. We validate the new code by presenting an extensive
series of stationary accretion flows either in spherical or axial symmetry and
performed either in 2D or 3D. In addition, we consider the highly nonlinear
scenario of a recoiling black hole produced in the merger of a supermassive
black hole binary interacting with the surrounding circumbinary disc. In this
way we can present, for the first time, ray-traced images of the shocked fluid
and the light-curve resulting from consistent general-relativistic
radiation-transport calculations from this process. The work presented here
lays the ground for the development of a generic computational infrastructure
employing AMR techniques to deal accurately and self-consistently with
accretion flows onto compact objects. In addition to the accurate handling of
the matter, we provide a self-consistent electromagnetic emission from these
scenarios by solving the associated radiative-transfer problem. While magnetic
fields are presently excluded from our analysis, the tools presented here can
have a number of applications to study accretion flows onto black holes or
neutron stars.Comment: 20 pages, 20 figures, accepted for publication in A&
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