Yu Feng's Portfolio > SPH->MESH: the OctTree flattened. by Yu Feng

An (incomplete) OCTtree is constructed with the particles in a cosmology SPH(smoothed particle hydrodynamics) simulation.

This octtree will be used as a smoothing kernel to reconstruct a density field out of SPH particles. The density field field will then be used in cosmic radiative transfer study, similar to Feng et al(2012, in prep) [http://arxiv.org/abs/1208.6544]

The construction method is based on the first step by Bern, M.; Eppstein, D.; Teng, S.-H. (1999)[doi:10.1142/S0218195999000303], but with a few optimizations designed for the parallel radiative transfer algorithm.

The plot is produced with an algorithm modifed from Shneiderman's 2D space-filling method[http://hcil2.cs.umd.edu/trs/91-03/91-03.html]. The algorithm is applied on the leaf nodes only. The tree is rendered in parallel into 64 puzzle pieces before they are combined into one single image shown here. The color corresponds to number of SPH particles in leaf nodes.

The black cells correspond to the spatial volume that is not occupied by any octtree nodes are of most interest. A black cell corresponds to a numerical artifact, because there they contain no SPH particles and the density becomes vacuum. Whether the artifact is a severe problem is still under investigation.