创建一个无限延伸的3D网格系统，随着距离增加网格逐渐淡出，支持自定义网格间距、颜色和最大可见距离。

class AdvancedGridHelper extends THREE.Mesh {
    constructor(
        minorSize = 10,
        majorSize = 100,
        color = new THREE.Color(0x8899aa),
        maxDistance = 10000,
        axes = 'xzy'
    ) {
        const geometry = new THREE.PlaneGeometry(2, 2, 1, 1);
        const planeAxes = axes.substring(0, 2);

        const material = new THREE.ShaderMaterial({
            side: THREE.DoubleSide,
            uniforms: {
                uMinorSize: { value: minorSize },
                uMajorSize: { value: majorSize },
                uColor: { value: color },
                uMaxDistance: { value: maxDistance }
            },
            transparent: true,
            // ... 着色器代码
        });

        super(geometry, material);
        this.frustumCulled = false;
    }
}

varying vec3 vWorldPos;
uniform float uMaxDistance;

void main() {
    // 计算世界空间位置
    vec3 pos = position.xzy * uMaxDistance;
    pos.xzy += cameraPosition.xzy;
    vWorldPos = pos;

    // 计算最终顶点位置
    gl_Position = projectionMatrix * modelViewMatrix * vec4(pos, 1.0);
}

varying vec3 vWorldPos;
uniform float uMinorSize;
uniform float uMajorSize;
uniform vec3 uColor;
uniform float uMaxDistance;

// 计算网格线函数
float getGridLine(float size) {
    vec2 gridCoords = vWorldPos.xzy / size;
    vec2 grid = abs(fract(gridCoords - 0.5) - 0.5) / fwidth(gridCoords);
    return 1.0 - min(min(grid.x, grid.y), 1.0);
}

void main() {
    // 计算距离衰减因子
    float distanceFactor = 1.0 - min(
        distance(cameraPosition.xzy, vWorldPos.xzy) / uMaxDistance,
        1.0
    );

    // 计算网格线
    float minorGrid = getGridLine(uMinorSize);
    float majorGrid = getGridLine(uMajorSize);

    // 混合网格线并应用衰减
    float gridAlpha = mix(majorGrid, minorGrid, minorGrid) * pow(distanceFactor, 3.0);

    // 主要网格线更粗
    gridAlpha = mix(gridAlpha * 0.5, gridAlpha, majorGrid);

    gl_FragColor = vec4(uColor, gridAlpha);

    if (gl_FragColor.a <= 0.0) discard;
}

const sky = new Sky();
sky.scale.setScalar(450000);

const skyUniforms = sky.material.uniforms;
skyUniforms.sunPosition.value = new THREE.Vector3().setFromSphericalCoords(
    1,
    THREE.MathUtils.degToRad(70),
    THREE.MathUtils.degToRad(190)
);
skyUniforms.rayleigh.value = 3.2;
skyUniforms.mieCoefficient.value = 0.005;
skyUniforms.mieDirectionalG.value = 0.8;