From 68ae62527fba1af4dc6994cdb9cc12684da2683a Mon Sep 17 00:00:00 2001
From: Max Richter <max@max-richter.dev>
Date: Thu, 7 May 2026 23:43:44 +0200
Subject: [PATCH] feat(noise): preserve segment lengths during displacement
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The noise node previously displaced each path point's XYZ independently,
which stretched/compressed segments and produced kinked edges. After
displacement, re-project each point onto the sphere of radius
seg_lens[i-1] centered at the previous point — same pattern used by the
gravity node. Total path length is now preserved; noise bends the path
rather than stretching it.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
---
 Cargo.lock                            |  1 +
 nodes/max/plantarium/noise/Cargo.toml |  1 +
 nodes/max/plantarium/noise/src/lib.rs | 73 ++++++++++++++++++++++-----
 3 files changed, 62 insertions(+), 13 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index cf43310..65725b6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -117,6 +117,7 @@ dependencies = [
 name = "noise"
 version = "0.1.0"
 dependencies = [
+ "glam",
  "nodarium_macros",
  "nodarium_utils",
  "noise 0.9.0",
diff --git a/nodes/max/plantarium/noise/Cargo.toml b/nodes/max/plantarium/noise/Cargo.toml
index 4d18f71..81f3a59 100644
--- a/nodes/max/plantarium/noise/Cargo.toml
+++ b/nodes/max/plantarium/noise/Cargo.toml
@@ -8,6 +8,7 @@ edition = "2018"
 crate-type = ["cdylib", "rlib"]
 
 [dependencies]
+glam = "0.30.10"
 nodarium_macros = { version = "0.1.0", path = "../../../../packages/macros" }
 nodarium_utils = { version = "0.1.0", path = "../../../../packages/utils" }
 noise = "0.9.0"
diff --git a/nodes/max/plantarium/noise/src/lib.rs b/nodes/max/plantarium/noise/src/lib.rs
index b54f684..9f7dee8 100644
--- a/nodes/max/plantarium/noise/src/lib.rs
+++ b/nodes/max/plantarium/noise/src/lib.rs
@@ -1,3 +1,4 @@
+use glam::Vec3;
 use nodarium_macros::nodarium_definition_file;
 use nodarium_macros::nodarium_execute;
 use nodarium_utils::{
@@ -65,24 +66,70 @@ pub fn execute(input: &[i32]) -> Vec<i32> {
 
             let length = path.get_length() as f64;
 
-            for i in 0..path.length {
+            // Record original segment lengths so we can re-project after displacement
+            let seg_lens: Vec<f32> = (0..path.length - 1)
+                .map(|k| {
+                    let p0 = Vec3::new(
+                        path.points[k * 4],
+                        path.points[k * 4 + 1],
+                        path.points[k * 4 + 2],
+                    );
+                    let p1 = Vec3::new(
+                        path.points[(k + 1) * 4],
+                        path.points[(k + 1) * 4 + 1],
+                        path.points[(k + 1) * 4 + 2],
+                    );
+                    (p1 - p0).length()
+                })
+                .collect();
+
+            // Displace the first point (fix_bottom=1 → scale=0 here, anchoring the base)
+            let scale0 = lerp(1.0, 0.0, fix_bottom);
+            path.points[0] += noise_x.get([j as f64, 0.0]) as f32
+                * directional_strength[0]
+                * strength
+                * scale0;
+            path.points[1] += noise_y.get([j as f64, 0.0]) as f32
+                * directional_strength[1]
+                * strength
+                * scale0;
+            path.points[2] += noise_z.get([j as f64, 0.0]) as f32
+                * directional_strength[2]
+                * strength
+                * scale0;
+            let mut prev = Vec3::new(path.points[0], path.points[1], path.points[2]);
+
+            for i in 1..path.length {
                 let a = i as f64 / (path.length - 1) as f64;
 
                 let px = j as f64 + a * length * scale;
                 let py = a * scale as f64;
 
-                path.points[i * 4] += noise_x.get([px, py]) as f32
-                    * directional_strength[0]
-                    * strength
-                    * lerp(1.0, a as f32, fix_bottom);
-                path.points[i * 4 + 1] += noise_y.get([px, py]) as f32
-                    * directional_strength[1]
-                    * strength
-                    * lerp(1.0, a as f32, fix_bottom);
-                path.points[i * 4 + 2] += noise_z.get([px, py]) as f32
-                    * directional_strength[2]
-                    * strength
-                    * lerp(1.0, a as f32, fix_bottom);
+                let sf = lerp(1.0, a as f32, fix_bottom);
+                path.points[i * 4] +=
+                    noise_x.get([px, py]) as f32 * directional_strength[0] * strength * sf;
+                path.points[i * 4 + 1] +=
+                    noise_y.get([px, py]) as f32 * directional_strength[1] * strength * sf;
+                path.points[i * 4 + 2] +=
+                    noise_z.get([px, py]) as f32 * directional_strength[2] * strength * sf;
+
+                // Re-project onto sphere of radius seg_lens[i-1] centered at prev
+                let cur = Vec3::new(
+                    path.points[i * 4],
+                    path.points[i * 4 + 1],
+                    path.points[i * 4 + 2],
+                );
+                let dir = cur - prev;
+                let dir_len = dir.length();
+                if dir_len > 0.0001 {
+                    let corrected = prev + dir * (seg_lens[i - 1] / dir_len);
+                    path.points[i * 4] = corrected.x;
+                    path.points[i * 4 + 1] = corrected.y;
+                    path.points[i * 4 + 2] = corrected.z;
+                    prev = corrected;
+                } else {
+                    prev = cur;
+                }
             }
             path_data
         })