feat: add perlin noise

src/tools/perlin_noise.cpp

@@ -0,0 +1,71 @@
+#include <Cubed/tools/perlin_noise.hpp>
+
+#include <Cubed/config.hpp>
+#include <Cubed/tools/cubed_assert.hpp>
+
+#include <algorithm>
+#include <numeric>
+#include <random>
+
+void PerlinNoise::init() {
+    p.resize(256);
+    std::iota(p.begin(), p.end(), 0);
+
+    std::mt19937 engine(SEED);
+    std::shuffle(p.begin(), p.end(), engine);
+
+    p.insert(p.end(), p.begin(), p.end());
+    is_init = true;
+}
+
+float PerlinNoise::noise(float x, float y, float z) {
+    CUBED_ASSERT_MSG(is_init, "The PerlinNoise don't init!");
+    int ix = static_cast<int>(std::floor(x)) & 255;
+    int iy = static_cast<int>(std::floor(y)) & 255;
+    int iz = static_cast<int>(std::floor(z)) & 255;
+
+    x -= std::floor(x);
+    y -= std::floor(y);
+    z -= std::floor(z);
+
+    double u = fade(x);
+    double v = fade(y);
+    double w = fade(z);
+
+    int a = p[ix] + iy;
+    int aa = p[a] + iz;
+    int ab = p[a + 1] + iz;
+    int b = p[ix + 1] + iy;
+    int ba = p[b] + iz;
+    int bb = p[b + 1] + iz;
+
+    float res = lerp (w,
+        lerp (v,
+            lerp(u, grad(p[aa], x, y, z), grad(p[ba], x - 1, y, z)),
+            lerp(u, grad(p[ab], x, y - 1, z), grad(p[bb], x - 1, y - 1, z))
+        ),
+        lerp(v,
+            lerp(u, grad(p[aa + 1], x, y, z - 1), grad(p[ba + 1], x - 1, y, z - 1)),
+            lerp(u, grad(p[ab + 1], x, y - 1, z - 1), grad(p[bb + 1 ], x - 1, y - 1, z - 1))
+        )
+        
+    );
+    return (res + 1.0f) / 2.0f;
+}
+
+float PerlinNoise::fade(float t) {
+    return t * t * t * (t * (t * 6 - 15) + 10);
+}
+
+float PerlinNoise::lerp(float t, float a, float b) {
+    return a + t * (b - a);
+}
+
+float PerlinNoise::grad(int hash, float x, float y, float z) {
+    int h = hash & 15;
+
+    float u = h < 8 ? x : y;
+    float v = h < 4 ? y : h == 12 || h == 14 ? x : z;
+
+    return ((h & 1) == 0 ? u : -u) + ((h & 2) == 0 ? v : -v);
+}