feat(core): add Perlin noise generator for terrain shaping

core/include/vf/Noise.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <array>
+#include <cstdint>
+
+namespace vf {
+
+// Improved Perlin noise (Ken Perlin, 2002) over a seeded permutation table.
+// Output of noise2D/noise3D is in the range [-1, 1].
+class PerlinNoise {
+public:
+    explicit PerlinNoise(uint32_t seed = 1337u) { reseed(seed); }
+
+    void reseed(uint32_t seed);
+
+    float noise2D(float x, float y) const;
+    float noise3D(float x, float y, float z) const;
+
+    // Fractal Brownian motion: sum of `octaves` scaled noise layers.
+    // Result normalised to roughly [-1, 1].
+    float fbm2D(float x, float y, int octaves, float lacunarity, float gain) const;
+
+private:
+    std::array<int, 512> perm;
+};
+
+} // namespace vf