From 9564ee92b631f4a038ffc06f2c89accf8a53e802 Mon Sep 17 00:00:00 2001
From: "max.nuding" <max.nuding@uni-konstanz.de>
Date: Wed, 6 Jul 2022 13:28:06 +0200
Subject: [PATCH] Add trilinear smoothing

---
 src/perlin.rs | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/src/perlin.rs b/src/perlin.rs
index d2605f0..3dfb3c9 100644
--- a/src/perlin.rs
+++ b/src/perlin.rs
@@ -26,11 +26,32 @@ impl Perlin {
     }
 
     pub fn noise(&self, point: &Point3) -> f64 {
+        /*
         let i = ((4.0 * point.x()) as i32) & 255;
         let j = ((4.0 * point.y()) as i32) & 255;
         let k= ((4.0 * point.z()) as i32) & 255;
         let idx = self.perm_x[i as usize] ^ self.perm_y[j as usize] ^ self.perm_z[k as usize];
         self.ranfloat[idx]
+        */
+        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: [[[f64; 2]; 2]; 2] = [[[0.0; 2]; 2]; 2];
+
+        for di in 0..2 {
+            for dj in 0..2 {
+                for dk in 0..2 {
+                    let idx = self.perm_x[((i+di) & 255) as usize] ^
+                        self.perm_y[((j+dj) & 255) as usize] ^
+                        self.perm_z[((k+dk) & 255) as usize];
+                    c[di as usize][dj as usize][dk as usize] = self.ranfloat[idx];
+                }
+            }
+        }
+        Perlin::trilinerar_interpolation(c, u, v, w)
     }
 
     fn perlin_generate_perm() -> Vec<usize> {
@@ -43,4 +64,22 @@ impl Perlin {
         });
         p
     }
+
+    fn trilinerar_interpolation(c: [[[f64; 2]; 2]; 2], u: f64, v: f64, w: f64) -> f64 {
+        let mut accum = 0.0;
+        for i in 0..2 {
+            for j in 0..2 {
+                for k in 0..2 {
+                    let ifl = i as f64;
+                    let jfl = j as f64;
+                    let kfl = k as f64;
+                    accum += (ifl*u + (1.0-ifl)*(1.0-u)) *
+                        (jfl*v + (1.0-jfl)*(1.0-v)) *
+                        (kfl*w + (1.0-kfl)*(1.0-w)) *
+                        c[i][j][k];
+                }
+            }
+        }
+        accum
+    }
 }