求助大佬有关 cesium 切割模型问题

cesium 中想实现一个功能, 沿着两点画一条线, 然后生成一个切割面, 可以切割模型, 但是现在问题是, 生成的切割面不是很正确, 下面是我的代码, 有大佬帮忙看看嘛

// 鼠标绘制的两个点
const start = linePoint[0]
const end = linePoint[1]

const direction = Cesium.Cartesian3.subtract(
end,
start,
new Cesium.Cartesian3()
)

const up = Cesium.Cartesian3.UNIT_Z
const normal = Cesium.Cartesian3.cross(direction, up, new Cesium.Cartesian3())
Cesium.Cartesian3.normalize(normal, normal)

clippingPlanes = new Cesium.ClippingPlaneCollection({
planes: [new Cesium.ClippingPlane(new Cesium.Cartesian3(1, normal.y, 0), 0)],
})
feature.clippingPlanes = clippingPlanes