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arXiv · 1902.08083

TREVR: A general $N log^2 N$ radiative transfer algorithm

J. J. Grond·R. M. Woods·J. W. Wadsley·H. M. P. Couchman
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Abstract

We present TREVR (Tree-based REVerse Ray Tracing), a general algorithm for computing the radiation field, including absorption, in astrophysical simulations. TREVR is designed to handle large numbers of sources and absorbers; it is based on a tree data structure and is thus suited to codes that use trees for their gravity or hydrodynamics solvers (e.g. Adaptive Mesh Refinement). It achieves computational speed while maintaining a specified accuracy via controlled lowering of the resolution of both sources and rays from each source. TREVR computes the radiation field in order ${N\log N_{source}}$ time without absorption and order ${N \log N_{source} \log{N}}$ time with absorption. These scalings arise from merging sources of radiation according to an opening angle criterion and walking the tree structure to trace a ray to a depth that gives the chosen accuracy for absorption. The absorption-depth refinement criterion is unique to TREVR. We provide a suite of tests demonstrating the algorithm's ability to accurately compute fluxes, ionization fronts and shadows.

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J. J. Grond, R. M. Woods, J. W. Wadsley, H. M. P. Couchman. 2019-02-21. TREVR: A general $N log^2 N$ radiative transfer algorithm. https://doi.org/10.1093/mnras%2Fstz525

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