cdshealpix-rust

CDS implementation of the HEALPix tesselation in Rust and modules to generate libraries in WebAssemnly, Python, ...

About

For informations on HEALPix in general, see:

• The official web site
• The Wikipedia page
• The two main related papers: Gorsky (2005) and Calabretta (2007)

See also the official page containing GPL v2 codes in Fortran, C++, Java, IDL, Python, ...

Other HEALPix implementations:

• Astropy-healpix python wrapper using a C code (C code by Dustin Lang)
• Javascript/Typescript implementation by Koike Michitaro
• ... (Help me to add links to other HEALPix resources and codes).

This library is mainly a port of a part of the CDS Java library available here.

Features

• Supports the HEALix Nested scheme
• Supports approximated cone and polygon queries
• Supports BMOC (MOC with a flag telling if a cell is fully or partially covered by a surface) as a result of cone and polygon queries

Missing Features

• Not supported
  • RING scheme
  • Spherical Harmonics computations
  • (Help me fill this)
• Not yet implemented
  • Exact cone and polygon solution
  • Logical operations on MOC/BMOC
  • MOC creation from arbritrary input

Examples

Compute the cell number of a given position on the unit-sphere at a given HEALPix depth.

use cdshealpix::{nside};
use cdshealpix::nested::{get_or_create, Layer};


let depth = 12_u8;
let lon = 12.5_f64.to_radians();
let lat = 89.99999_f64.to_radians();

let nested_d12 = get_or_create(depth);
let nside = nside(depth) as u_64;
let expected_cell_number = nside * nside - 1

assert_eq!(expected_cell_number, nested_d12.hash(lon, lat));

Get the spherical coorinates of the 4 vertices of a given cell at a given depth:

use cdshealpix::nested::{get_or_create, Layer};

let depth = 12_u8;
let cell_number= 10_u64;

let nested_d12 = get_or_create(depth);

let [
  (lon_south, lat_south), 
  (lon_east,  lat_east), 
  (lon_north, lat_north), 
  (lon_west,  lat_west)
] = nested_d12.vertices(cell_number);

Get a hierarchical view (a MOC) on the cells overlapped by a given cone:

use cdshealpix::nested::{get_or_create, Layer};

let depth = 6_u8;
let nested_d6 = get_or_create(depth);

let lon = 13.158329_f64.to_radians();
let lat = -72.80028_f64.to_radians();
let radius = 5.64323_f64.to_radians();
 
let moc = nested_d6.cone_overlap_approx(lon, lat, radius);
for cell in moc.into_iter() {
    println!("cell: {:?}", cell);
}

Standalone

(Not on crates.io, but on github) The code source of the very beginning of a standalone exec can be found in cli/src/bin.rs.

WebAssembly

(Not on crates.io, but on github) To build and use the WebAssembly (and Javascript) files, the libwasmbingen directory. We rely on wasm-bingen.

Python

(Not on crates.io, but on github) See the libpython directory containing so far a very basic python script showing how to use the library from python.

We are currently working on making a clean Python wrapper and generating Python Wheels for a simple install through pip. See the Matthieu Baumann's project here on github.

License

Like most projects in Rust, this project is licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this project by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Disclaimer

It a first code in Rust, feel free to give some advice/feedback.