From a51fed5026f760e0ab84e271c9c90aefe0e12c1d Mon Sep 17 00:00:00 2001
From: Niklas Korz <niklas@niklaskorz.de>
Date: Mon, 31 Mar 2025 18:27:54 +0200
Subject: [PATCH] Simplex noise for elevation

---
 Cargo.lock  | 21 +++++++++++++++++++++
 Cargo.toml  |  1 +
 src/main.rs | 33 +++++++++++++++++++++++++++------
 3 files changed, 49 insertions(+), 6 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 0482e7e..2efb3ee 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2876,6 +2876,17 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "noise"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6da45c8333f2e152fc665d78a380be060eb84fad8ca4c9f7ac8ca29216cff0cc"
+dependencies = [
+ "num-traits",
+ "rand 0.8.5",
+ "rand_xorshift",
+]
+
 [[package]]
 name = "nom"
 version = "7.1.3"
@@ -2898,6 +2909,7 @@ version = "0.1.0"
 dependencies = [
  "bevy",
  "bevy_vello",
+ "noise",
  "rand 0.9.0",
  "voronator",
 ]
@@ -3549,6 +3561,15 @@ dependencies = [
  "rand 0.8.5",
 ]
 
+[[package]]
+name = "rand_xorshift"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d25bf25ec5ae4a3f1b92f929810509a2f53d7dca2f50b794ff57e3face536c8f"
+dependencies = [
+ "rand_core 0.6.4",
+]
+
 [[package]]
 name = "range-alloc"
 version = "0.1.4"
diff --git a/Cargo.toml b/Cargo.toml
index d6f24d5..4d10ee4 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,5 +14,6 @@ opt-level = 3
 [dependencies]
 bevy = "0.15.3"
 bevy_vello = "0.7.1"
+noise = "0.9.0"
 rand = "0.9.0"
 voronator = "0.2.1"
diff --git a/src/main.rs b/src/main.rs
index a318d6f..8cfc354 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -4,9 +4,10 @@ use bevy_vello::{
     prelude::*,
     vello::kurbo::{PathEl, Point},
 };
+use noise::{NoiseFn, Simplex};
 use rand::Rng;
-use voronator::VoronoiDiagram;
 use std::ops::DerefMut;
+use voronator::VoronoiDiagram;
 
 const JITTER: f64 = 0.5;
 
@@ -39,13 +40,23 @@ fn draw_map(mut query_scene: Single<(&mut Transform, &mut VelloScene)>) {
             ));
         }
     }
-    let diagram = VoronoiDiagram::<voronator::delaunator::Point>::from_tuple(&(-20.0, -10.0), &(20.0, 10.0), &points).unwrap();
+    let diagram = VoronoiDiagram::<voronator::delaunator::Point>::from_tuple(
+        &(-20.0, -10.0),
+        &(20.0, 10.0),
+        &points,
+    )
+    .unwrap();
 
+    let noise = Simplex::new(rng.random());
     for cell in diagram.cells() {
         let mut first = true;
         let mut path = Vec::new();
+        let mut center = Point::new(0.0, 0.0);
+        let points = cell.points().len() as f64;
         for point in cell.points() {
             let point = Point::new(point.x, point.y);
+            center.x += point.x / points;
+            center.y += point.y / points;
             if first {
                 first = false;
                 path.push(PathEl::MoveTo(point));
@@ -53,13 +64,23 @@ fn draw_map(mut query_scene: Single<(&mut Transform, &mut VelloScene)>) {
                 path.push(PathEl::LineTo(point));
             }
         }
-        let r = rng.random_range(0..=255);
-        let g = rng.random_range(0..=255);
-        let b = rng.random_range(0..=255);
+
+        let nx = (center.x + 20.0) / 40.0 - 0.5;
+        let ny = (center.y + 10.0) / 20.0 - 0.5;
+
+        let elevation = (1.0 + noise.get([nx / 0.5, ny / 0.5])) / 2.0;
+        let d = 2.0 * nx.abs().max(ny.abs());
+        let elevation = (1.0 + elevation - d) / 2.0;
+
+        let color = if elevation < 0.5 {
+            peniko::Color::from_rgb8(89, 89, 166)
+        } else {
+            peniko::Color::from_rgb8(128, 153, 102)
+        };
         scene.fill(
             peniko::Fill::NonZero,
             kurbo::Affine::default(),
-            peniko::Color::from_rgb8(r, g, b),
+            color,
             None,
             &kurbo::BezPath::from_vec(path),
         );