Function curvatures_core 

pub fn curvatures_core(
    dem: ArrayView2<'_, f32>,
    cellsize: f32,
    profile_out: &mut Array2<f32>,
    planform_out: &mut Array2<f32>,
)

Compute profile and planform curvature of a DEM.

Profile curvature is curvature in the direction of steepest slope (affects flow acceleration); planform curvature is curvature perpendicular to it (affects flow convergence). Both use the Zevenbergen & Thorne sign convention of derivatives.py.

Arguments

• dem - ArrayView2<f32>, shape (H, W): elevations. Must be NaN-free (see module docs). Any memory layout. H and W should each be at least 2; see Edge cases.
• cellsize - f32: grid spacing, in the same units as the elevations, applied to both axes.
• profile_out - &mut Array2<f32>, shape (H, W), C-contiguous: overwritten with profile curvature.
• planform_out - &mut Array2<f32>, shape (H, W), C-contiguous: overwritten with planform curvature.

Flat cells and any non-finite results are written as 0.0.

Runs serially below PARALLEL_THRESHOLD elements and in parallel at or above it. The gradient passes themselves always run serially.

Edge cases

Where numpy’s np.gradient would raise ValueError because an axis has length 1, this treats that axis’s derivatives as zero instead.

Panics

• If profile_out or planform_out is not C-contiguous. Arrays made with Array2::zeros(shape) always are.
• If profile_out or planform_out has more elements than dem.
• If exactly one of H and W is 0.

Output shapes are not otherwise checked: outputs with fewer elements than dem are partly filled, and a different shape with the same element count is filled in the wrong layout. Always allocate both outputs with dem.raw_dim().

Example

use ndarray::Array2;
use terra_texture_rs::curvatures_core;

// a uniformly tilted plane has no curvature anywhere
let dem = Array2::from_shape_fn((5, 5), |(i, j)| (i + 2 * j) as f32);
let mut profile = Array2::<f32>::zeros(dem.raw_dim());
let mut planform = Array2::<f32>::zeros(dem.raw_dim());
curvatures_core(dem.view(), 1.0, &mut profile, &mut planform);

assert!(profile.iter().all(|&v| v.abs() < 1e-6));
assert!(planform.iter().all(|&v| v.abs() < 1e-6));