珀林噪声在Y轴上获得错误的值(C++)

#include <iostream>
#include <cmath>

double fade(double t) {
    return t * t * t * (t * (t * 6 - 15) + 10);
}

double lerp(double t, double a, double b) {
    return a + t * (b - a);
}

double grad(int hash, double x, double y, double z) {
    int h = hash & 15;
    double u = h < 8 ? x : y;
    double v = h < 4 ? y : h == 12 || h == 14 ? x : z;
    return ((h & 1) ? -u : u) + ((h & 2) ? -v : v);
}

double noise(double x, double y, double z) {
    int X = (int)floor(x) & 255;
    int Y = (int)floor(y) & 255;
    int Z = (int)floor(z) & 255;

    x -= floor(x);
    y -= floor(y);
    z -= floor(z);

    double u = fade(x);
    double v = fade(y);
    double w = fade(z);

    int A = p[X] + Y;
    int AA = p[A] + Z;
    int AB = p[A + 1] + Z;
    int B = p[X + 1] + Y;
    int BA = p[B] + Z;
    int BB = p[B + 1] + Z;

    return 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))));
}

int main() {
    // 初始化随机种子
    srand(time(NULL));

    // 生成珀林噪声
    double x = 0.5;
    double y = 0.5;
    double z = 0.5;
    double result = noise(x, y, z);

    std::cout << "Perlin Noise value at (" << x << ", " << y << ", " << z << "): " << result << std::endl;

    return 0;
}