fix map.pointAtResToAltitude when point < 0 which caused jumping when moving map with terrain below sea level

Author: fuzhenn

packages/maptalks/src/map/Map.Camera.ts

@@ -914,7 +914,7 @@ Map.include(/** @lends Map.prototype */{
             // remains previous center altitude if queried altitude is null
             queriedAltitude = this.centerAltitude;
         }
-        const centerAltitude = queriedAltitude || 0;
+        const centerAltitude = queriedAltitude > 0 && queriedAltitude || 0;
         const pitch = this.getPitch() * RADIAN;
         const bearing = this.getBearing() * RADIAN;
         const altDist = (centerAltitude - this.centerAltitude) * this._meterToGLPoint;

packages/maptalks/src/map/Map.CoordTransform.ts

@@ -372,23 +372,20 @@ Map.include(/** @lends Map.prototype */{
                 this._altitudeOriginDirty = false;
             }
             const p = this.distanceToPointAtRes(altitude, altitude, res, originCenter || DEFAULT_CENTER, POINT);
-            if (altitude < 0 && p.x > 0) {
-                p.x = -p.x;
-            }
             const heightFactor = this.options['heightFactor'];
             if (heightFactor && heightFactor !== 1) {
                 p.x *= heightFactor;
                 p.y *= heightFactor;
             }
-            return p.x;
+            return p.x * Math.sign(altitude);
         };
     }(),
 
     pointAtResToAltitude: function () {
         const DEFAULT_CENTER = new Coordinate(0, 40);
         return function (point = 0, res, originCenter) {
             const altitude = this.pointAtResToDistance(point, 0, res, originCenter || DEFAULT_CENTER);
-            return altitude;
+            return altitude * Math.sign(point);
         };
     }(),