From 78ddaff5855bf8446adef9e18eb0d7b7ddcee52a Mon Sep 17 00:00:00 2001
From: lamp
Date: Sun, 5 Mar 2023 21:45:56 +0000
Subject: init

---
 src/texture/perlin.rs | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 98 insertions(+)
 create mode 100644 src/texture/perlin.rs

(limited to 'src/texture/perlin.rs')

diff --git a/src/texture/perlin.rs b/src/texture/perlin.rs
new file mode 100644
index 0000000..43d8f64
--- /dev/null
+++ b/src/texture/perlin.rs
@@ -0,0 +1,98 @@
+use crate::vec3::{Vec3, Point3};
+
+const POINT_COUNT: usize = 256;
+
+pub struct Perlin {
+    ranvec: Vec<Vec3>,
+    perm_x: Vec<usize>,
+    perm_y: Vec<usize>,
+    perm_z: Vec<usize>,
+}
+
+impl Perlin {
+    pub fn new() -> Self {
+        let mut ranvec = Vec::with_capacity(POINT_COUNT);
+        for _ in 0..POINT_COUNT {
+            ranvec.push(Vec3::random_in_range(-1.0, 1.0).unit_vector());
+        }
+        Self {
+            ranvec,
+            perm_x: Self::generate_perm(),
+            perm_y: Self::generate_perm(),
+            perm_z: Self::generate_perm(),
+        }
+    }
+
+    pub fn turb(&self, point: &Point3, depth: u32) -> f64 {
+        let mut accum = 0.0;
+        let mut temp_point = point.clone();
+        let mut weight = 1.0;
+
+        for _ in 0..depth {
+            accum += weight * self.noise(&temp_point);
+            weight *= 0.5;
+            temp_point *= 2.0;
+        }
+        accum.abs()
+    }
+
+    pub fn noise(&self, point: &Point3) -> f64 {
+        let u = point.x - point.x.floor();
+        let v = point.y - point.y.floor();
+        let w = point.z - point.z.floor();
+        let i = point.x.floor() as i32;
+        let j = point.y.floor() as i32;
+        let k = point.z.floor() as i32;
+        let mut c: [[[Vec3; 2]; 2]; 2] = Default::default();
+        for di in 0..2 {
+            for dj in 0..2 {
+                for dk in 0..2 {
+                    c[di][dj][dk] = self
+                        .ranvec
+                        .get(
+                            (self.perm_x.get(((i + di as i32) & 255) as usize).unwrap()
+                                ^ self.perm_y.get(((j + dj as i32) & 255) as usize).unwrap()
+                                ^ self.perm_z.get(((k + dk as i32) & 255) as usize).unwrap())
+                                as usize,
+                        )
+                        .unwrap().clone();
+                }
+            }
+        }
+        Self::trilinear_interpolate(c, u, v, w)
+    }
+
+    fn trilinear_interpolate(c: [[[Vec3; 2]; 2]; 2], u: f64, v: f64, w: f64) -> f64 {
+        let uu = u * u * (3.0 - 2.0 * u);
+        let vv = v * v * (3.0 - 2.0 * v);
+        let ww = w * w * (3.0 - 2.0 * w);
+        let mut accum: f64 = 0.0;
+        for i in 0..2 {
+            for j in 0..2 {
+                for k in 0..2 {
+                    let i_f = i as f64;
+                    let j_f = j as f64;
+                    let k_f = k as f64;
+                    let weight_v = Vec3 { x: u - i_f, y: v - j_f, z: w - k_f };
+                    accum += (i_f * uu + (1.0 - i_f) * (1.0 - uu)) *
+                        (j_f * vv + (1.0 - j_f) * (1.0 - vv)) *
+                        (k_f * ww + (1.0 - k_f) * (1.0 - ww)) *
+                        c[i][j][k].dot(&weight_v);
+                }
+            }
+        }
+        accum
+    }
+
+    fn generate_perm() -> Vec<usize> {
+        let mut p = (0..POINT_COUNT).collect();
+        Self::permute(&mut p, POINT_COUNT);
+        p
+    }
+
+    fn permute(p: &mut Vec<usize>, n: usize) {
+        for i in (1..n).rev() {
+            p.swap(i, rand::random::<usize>() % i);
+        }
+    }
+}
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