assign random color per triangle

src/planet.rs

@@ -1,15 +1,20 @@
+//use core::slice::SlicePattern;
+
 use bevy::{
     prelude::{shape::Icosphere, *},
-    render::mesh::Indices,
+    render::{color::Color, mesh::Indices},
 };
 use bevy_rapier3d::prelude::*;
 use hexasphere::shapes::IcoSphere;
 use noise::{HybridMulti, NoiseFn, SuperSimplex};
+use rand::{Rng, SeedableRng};
 use wgpu::PrimitiveTopology;
 
 use crate::Label;
 
 pub const PLANET_RADIUS: f32 = 3_000.0;
+pub const PLANET_HUE: f32 = 31.0;
+pub const PLANET_SATURATION: f32 = 1.0;
 
 #[derive(Component)]
 pub struct CyberPlanet;
@@ -19,7 +24,7 @@ fn spawn_planet(
     mut meshes: ResMut<Assets<Mesh>>,
     mut materials: ResMut<Assets<StandardMaterial>>,
 ) {
-    let color = Color::rgb(0.74, 0.5334, 0.176);
+    //let color = Color::rgb(0.74, 0.5334, 0.176);
     let isphere = Icosphere {
         radius: PLANET_RADIUS,
         subdivisions: 88,
@@ -41,14 +46,7 @@ fn spawn_planet(
     commands
         .spawn(PbrBundle {
             mesh: meshes.add(mesh),
-            material: materials.add(StandardMaterial {
-                base_color: color,
-                metallic: 0.3,
-                perceptual_roughness: 0.3,
-                //alpha_mode: AlphaMode::Opaque,
-                ..Default::default()
-            }),
-
+            material: materials.add(Color::WHITE.into()),
             ..Default::default()
         })
         .insert(pbody)
@@ -82,11 +80,13 @@ fn gen_planet(sphere: Icosphere) -> (Mesh, Collider) {
 
     let noise = HybridMulti::<SuperSimplex>::default();
 
+    let (mut min, mut max) = (f32::MAX, f32::MIN);
+
     let noisy_points = generated
         .raw_points()
         .iter()
         .map(|&p| {
-            let disp = noise.get(p.as_dvec3().into()) as f32 * 0.01;
+            let disp = noise.get(p.as_dvec3().into()) as f32 * 0.05;
             let pt = p + (p.normalize() * disp);
             pt.into()
         })
@@ -97,6 +97,13 @@ fn gen_planet(sphere: Icosphere) -> (Mesh, Collider) {
         .map(|&p| (Vec3::from_slice(&p) * sphere.radius).into())
         .collect::<Vec<[f32; 3]>>();
 
+    for p in &points {
+        let v = Vec3::new(p[0], p[1], p[2]);
+        let v = v.length();
+        min = v.min(min);
+        max = v.max(max);
+    }
+
     let uvs = generated.raw_data().to_owned();
 
     let mut indices = Vec::with_capacity(generated.indices_per_main_triangle() * 20);
@@ -110,13 +117,53 @@ fn gen_planet(sphere: Icosphere) -> (Mesh, Collider) {
         idxs.push([idx[0], idx[1], idx[2]]);
     }
 
+    let indices = Indices::U32(indices);
     let shape = Collider::trimesh(points.iter().map(|p| Vect::from_slice(p)).collect(), idxs);
 
-    let indices = Indices::U32(indices);
+    dbg!(&points.len());
 
     let mut mesh = Mesh::new(PrimitiveTopology::TriangleList);
     mesh.set_indices(Some(indices));
     mesh.insert_attribute(Mesh::ATTRIBUTE_POSITION, points);
-    mesh.insert_attribute(Mesh::ATTRIBUTE_UV_0, uvs);
+    //mesh.insert_attribute(Mesh::ATTRIBUTE_UV_0, uvs);
+    mesh.duplicate_vertices();
+    mesh.compute_flat_normals();
+
+    let tri_list = mesh
+        .attribute(Mesh::ATTRIBUTE_POSITION)
+        .unwrap()
+        .as_float3()
+        .unwrap();
+
+    dbg!(&tri_list.len());
+
+    let mut rng = rand::rngs::StdRng::seed_from_u64(57);
+    let mut colors = Vec::new();
+    for triangle in tri_list.chunks_exact(3) {
+        let mut lens = 0.0;
+        for &v in triangle {
+            let v = Vec3::new(v[0], v[1], v[2]);
+            lens += v.length();
+        }
+        let v = lens / 3.0;
+        //let l = val_norm(v, min - 500.0, max); //.powi(2);
+        let l = 0.41;
+        let jitter = rng.gen_range(-0.0..=360.0f32);
+        let h = jitter;
+        let color = Color::hsl(h, PLANET_SATURATION, l).as_linear_rgba_f32();
+        for _ in 0..3 {
+            colors.push(color.clone());
+        }
+    }
+
+    dbg!(&colors.len());
+    mesh.insert_attribute(Mesh::ATTRIBUTE_COLOR, colors);
+
     (mesh, shape)
 }
+
+/// remaps v in low..high to 0..1
+fn val_norm(v: f32, low: f32, high: f32) -> f32 {
+    // q = (p-A)*(D-C)/(B-A) + C, C = 0, D = 1
+    (v - low) / (high - low)
+}