SurtGIS Relief

Rayshader-style shaded-relief compositing on top of the terrain primitives that already live in surtgis-algorithms. This crate is a compositor, not a new set of algorithms — see SPEC_SURTGIS_RELIEF.md in the repository root for the full design.

What lives here

• ray_shade — ray-traced cast shadows via surtgis_algorithms::terrain::horizon_angle_map_fast, with optional soft-shadow averaging over multiple sun samples.
• sphere_shade — normal-based hillshade as an intensity layer in [0, 1], wrapping surtgis_algorithms::terrain::hillshade.

What is re-exported

Pixel-buffer and PNG output live in surtgis_colormap; we re-export the relevant types at the crate root for ergonomics.

use surtgis_relief::{ray_shade, sphere_shade, RayShadeParams, SunSample, RgbaImage};

let shadow_mask = ray_shade(&dem, &RayShadeParams::default())?;
let mut img = RgbaImage::from_intensity(&sphere_shade(&dem, Default::default())?);
let shadow_layer = RgbaImage::from_intensity(&shadow_mask);
img.multiply(&shadow_layer, 0.5)?;
img.save_png("relief.png")?;