cell-map: many-layer 2D cellular maps

This crate provides the CellMap type, a 2D map with many layers comprised of cells that can store arbitrary data. It is based on ANYbotics/grid_map, a C++ ROS package which provides the same type of data structre.

CellMap uses ndarray::Array2 to store its data in an efficient and scalable format. It also uses nalgebra types for expressing vectors and points.

Getting Started

Layers

Each layer of the cell map is represented by its own ndarray::Array2 array. The map indexes each layer by an enum implementing the Layer trait. A derive macro is provided to simplify this, for example:

use cell_map::Layer;

#[derive(Layer, Clone, Debug)]
enum MyLayer {
    Height,
    Gradient,
    Roughness
}

The Layer trait is required to be Clone, and is recommended to be Debug.

Creating a CellMap

To create a new map:

use cell_map::{CellMap, CellMapParams, Layer};
use nalgebra::Vector2;

// Creates a new 5x5 map where each cell is 1.0 units wide, which is centred on (0, 0), with
// all elements initialised to 1.0.
let my_map = CellMap::<MyLayer, f64>::new_from_elem(
    CellMapParams {
        cell_size: Vector2::new(1.0, 1.0),
        cell_bounds: Bounds::new((0, 5), (0, 5)).unwrap(),
        centre: Vector2::new(0.0, 0.0),
    },
    1.0,
);

Iterating Over Cells

CellMap provides methods to produce iterators over its data:

• CellMap::iter() gives an iterator over all cells in every layer of the map
• CellMap::window_iter() gives an iterator over rectangular windows into the map.
• CellMap::line_iter() gives an iterator of cells between two world points

All iterators also provide a mutable variant, and more iterators are planned in the future!

You can modify iterators so they produce their indexes, as well as controlling which layers the data comes from. See iterators for more information.

// Check all the cells in our map are 1, this will be true
assert!(my_map.iter().all(|&v| v == 1.0));

// Use a window iterator to change all cells not on the border of the map to 2
my_map.window_iter_mut(Vector2::new(1, 1)).unwrap().for_each(|mut v| {
    v[(1, 1)] = 2.0;
});

// Overwrite all values on the Roughness layer to be zero
my_map.iter_mut().layer(MyLayer::Roughness).for_each(|v| *v = 0.0);

// Check that our map is how we expect it
for ((layer, cell), &value) in my_map.iter().indexed() {
    if matches!(layer, MyLayer::Roughness) {
        assert_eq!(value, 0.0);
    }
    else if cell.x == 0 || cell.x == 4 || cell.y == 0 || cell.y == 4 {
        assert_eq!(value, 1.0);
    }
    else {
        assert_eq!(value, 2.0);
    }
}