tz-onest-data/data-ui/public/SuperMap3D/examples/webgl/js/curve.js

 /**
   * 根据弧线的坐标节点数组
   */
  function getCurvePoints(points, options) {
    options = options || {};
    var curvePoints = [];
    for (var i = 0; i < points.length - 1; i++) {
      var p = getCurveByTwoPoints(points[i], points[i + 1], options.count);
      if (p && p.length > 0) {
        curvePoints = curvePoints.concat(p);
      }
    }
    return curvePoints;
  }

  /**
   * 根据两点获取曲线坐标点数组
   * @param Point 起点
   * @param Point 终点
   */
  function getCurveByTwoPoints(obj1, obj2, count) {
    if (!obj1 || !obj2) {
      return null;
    }

    var B1 = function(x) {
      return 1 - 2 * x + x * x;
    };
    var B2 = function(x) {
      return 2 * x - 2 * x * x;
    };
    var B3 = function(x) {
      return x * x;
    };

    var curveCoordinates = [];

    var count = count || 40; // 曲线是由一些小的线段组成的，这个表示这个曲线所有到的折线的个数
    var isFuture = false;
    var t, h, h2, lat3, lng3, j, t2;
    var LnArray = [];
    var i = 0;
    var inc = 0;

    if (typeof(obj2) == "undefined") {
      if (typeof(curveCoordinates) != "undefined") {
        curveCoordinates = [];
      }
      return;
    }

    var lat1 = parseFloat(obj1.lat);
    var lat2 = parseFloat(obj2.lat);
    var lng1 = parseFloat(obj1.lng);
    var lng2 = parseFloat(obj2.lng);
      
    // 计算曲线角度的方法
    if (lng2 > lng1) {
      if (parseFloat(lng2-lng1) > 180) {
        if (lng1 < 0) {
          lng1 = parseFloat(180 + 180 + lng1);
        }
      }
    }
    
    if (lng1 > lng2) {
      if (parseFloat(lng1-lng2) > 180) {
        if (lng2 < 0) {
          lng2 = parseFloat(180 + 180 + lng2);
        }
      }
    }
    j = 0;
    t2 = 0;
    if (lat2 == lat1) {
      t = 0;
      h = lng1 - lng2;
    } else if (lng2 == lng1) {
      t = Math.PI / 2;
      h = lat1 - lat2;
    } else {
      t = Math.atan((lat2 - lat1) / (lng2 - lng1));
      h = (lat2 - lat1) / Math.sin(t);
    }
    if (t2 == 0) {
      t2 = (t + (Math.PI / 5));
    }
    h2 = h / 2;
    lng3 = h2 * Math.cos(t2) + lng1;
    lat3 = h2 * Math.sin(t2) + lat1;

    for (i = 0; i < count + 1; i++) {
      curveCoordinates.push([
        (lng1 * B1(inc) + lng3 * B2(inc)) + lng2 * B3(inc),
        (lat1 * B1(inc) + lat3 * B2(inc) + lat2 * B3(inc))
      ]);
      inc = inc + (1 / count);
    }
    return curveCoordinates;
  }

function Point (lng, lat) {
    this.lng = lng;
    this.lat = lat;
}