ridge-core

The terrain pipeline behind ridge_redux: a Rust port of the Python package ridge_map ("3D maps with 1D lines"), without matplotlib.

It turns a bounding box into ridgeline artwork:

1. Fetch SRTM elevation tiles from a mirror, cached on disk (srtm).
2. Sample a grid of lines over the box (grid). The sampling is bit-for-bit identical to ridge_map's, checked against its test fixture.
3. Rotate to a viewpoint angle, like scipy.ndimage.rotate (rotate).
4. Mask water and lakes, and exaggerate the relief (preprocess).
5. Lay out the ridge rows as a matplotlib-style figure (geometry) and write SVG (svg).

Command line

cargo install ridge-core installs render, which draws one map to SVG:

render --bbox "11.098251,47.264786,11.695633,47.453630" \
  --num-lines 150 --vertical-ratio 240 --lake-flatness 2 \
  --label "Karwendelgebirge" --label-x 0.55 --label-y 0.1 --label-size 40 \
  --out karwendel.svg

render --help lists every option. For an interactive editor (pick the area on a map, rotate and restyle live), use cargo install ridge_redux.

Library

use ridge_core::colormap::{hex, LineColor};
use ridge_core::geometry::{build_scene, ColorKind};
use ridge_core::srtm::RemoteSource;
use ridge_core::svg::{render_svg, LineColorSpec, PlotStyle};
use ridge_core::Bbox;

fn main() -> ridge_core::Result<()> {
    // Downloads tiles on first use and caches them in srtm::default_cache_dir().
    let source = RemoteSource::default_paths()?;
    let white_mountains = Bbox::new(-71.928864, 43.758201, -70.957947, 44.465151);
    let scene = build_scene(
        &source,
        &white_mountains,
        80, 300,              // lines, points per line
        0.0, false, 0, false, // viewpoint angle, crop, interpolation, lock resolution
        10.0, 3, 40.0,        // water percentile, lake flatness, vertical ratio
        20.0,                 // figure width in inches
    )?;
    let style = PlotStyle {
        line: LineColorSpec::from(&LineColor::parse("black").unwrap()),
        kind: ColorKind::Gradient,
        background: hex("#ece8ec"),
        linewidth_pt: 2.0,
        size_scale: 20.0,
        label: None,
        annotation: None,
    };
    std::fs::write("white_mountains.svg", render_svg(&scene, &style))?;
    Ok(())
}

srtm::DirSource reads .hgt tiles from a directory instead, for offline use. SRTM covers latitudes between 60°S and 60°N.

License

MIT. ridge-core is a port of ridge_map, also MIT, whose copyright notice is kept in LICENSE-upstream.

Elevation data: NASA Shuttle Radar Topography Mission.