“任意多边形地形开挖” 是“地形开挖”的补充篇,在这节里,我们介绍关于如何使用任意多边形对地形进行开挖,同时,由于有不少小伙伴也咨询了关于“地形开挖”篇后序内容中的填充地形的效果,之前没放出来,是想让小伙伴有个思考的过程,现在放出来,也是提供一种解决方法。
效果图
直接上代码说明方法
1、使用鼠标交互事件,采集需要开挖的范围
注: 这里要特别注意一点,为了下面的计算 ClippingPlane 方便,采集点顺序最好是 逆时针,如果点集的组织是顺时针,需要首先逆序成逆时针,关于如果判断一个点集是否是顺时针或者是逆时针,可以用向量法求多边形面积的方式,如果为正,则为顺时针,否者为逆时针。或者使用JS插件计算,比如turf.js。
- var points = [
- new Cesium.Cartesian3(-1715292.6999753984, 4993153.157628936, 3566663.752912529),
- new Cesium.Cartesian3(-1715285.8150713604, 4993167.072601330,3566647.6921528564),
- new Cesium.Cartesian3(-1715286.5985765400, 4993181.309761941, 3566627.519787549),
- new Cesium.Cartesian3(-1715299.0249209427, 4993191.177501195, 3566607.861264360),
- new Cesium.Cartesian3(-1715349.5762367432, 4993176.675656664, 3566603.878289345),
- new Cesium.Cartesian3(-1715375.5538853381, 4993159.990032478, 3566614.671147202),
- new Cesium.Cartesian3(-1715370.1945772346, 4993141.041835706, 3566643.580587877),
- new Cesium.Cartesian3(-1715359.7019716015, 4993131.063945592, 3566662.468046927),
- new Cesium.Cartesian3(-1715321.9141253997, 4993137.762602262, 3566671.205164391)
- ];
2、根据点集计算 ClippingPlane (这个计算方式来源于官网示例)
- var pointsLength = points.length;
- var clippingPlanes = []; // 存储ClippingPlane集合
- for (var i = 0; i < pointsLength; ++i) {
- var nextIndex = (i + 1) % pointsLength;
- var midpoint = Cesium.Cartesian3.add(points[i], points[nextIndex], new Cesium.Cartesian3());
- midpoint = Cesium.Cartesian3.multiplyByScalar(midpoint, 0.5, midpoint);
- var up = Cesium.Cartesian3.normalize(midpoint, new Cesium.Cartesian3());
- var right = Cesium.Cartesian3.subtract(points[nextIndex], midpoint, new Cesium.Cartesian3());
- right = Cesium.Cartesian3.normalize(right, right);
- var normal = Cesium.Cartesian3.cross(right, up, new Cesium.Cartesian3());
- normal = Cesium.Cartesian3.normalize(normal, normal);
- var originCenteredPlane = new Cesium.Plane(normal, 0.0);
- var distance = Cesium.Plane.getPointDistance(originCenteredPlane, midpoint);
- clippingPlanes.push(new Cesium.ClippingPlane(normal, distance));
- }
3、赋值给globe的 clippingPlanes 属性
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原文地址:https://www.cnblogs.com/giserhome/p/11641867.html
时间: 2024-10-02 16:30:47