Improvement for camera 3d moving (#2340)

lib/graph3d/Graph3d.js

@@ -1910,6 +1910,8 @@ Graph3d.prototype._onMouseDown = function(event) {
   // get mouse position (different code for IE and all other browsers)
   this.startMouseX = getMouseX(event);
   this.startMouseY = getMouseY(event);
+  
+  this._startCameraOffset = this.camera.getOffset();
 
   this.startStart = new Date(this.start);
   this.startEnd = new Date(this.end);
@@ -1936,21 +1938,28 @@ Graph3d.prototype._onMouseDown = function(event) {
  */
 Graph3d.prototype._onMouseMove = function (event) {
   event = event || window.event;
-
+  
     // move with ctrl or rotate by other
   if (event && event.ctrlKey === true) {
       // calculate change in mouse position
       var camera = this.camera,
           offset = camera.getOffset();
+	  
       var diffX = parseFloat(getMouseX(event)) - this.startMouseX;
       var diffY = parseFloat(getMouseY(event)) - this.startMouseY;
 
-      var scale = this.frame.clientWidth * 0.6;
-
-      var offXNew = offset.x - ((diffX / scale) * this.camera.armLength) * 0.1;
-      var offYNew = offset.y + ((diffY / scale) * this.camera.armLength) * 0.1;
+      var scaleX = this.frame.clientWidth * 0.5;
+	  var scaleY = this.frame.clientHeight * 0.5;
 
+      var offXNew = (this._startCameraOffset.x || 0) - ((diffX / scaleX) * this.camera.armLength) * 0.8;
+      var offYNew = (this._startCameraOffset.y || 0) + ((diffY / scaleY) * this.camera.armLength) * 0.8;
+	  
       this.camera.setOffset(offXNew, offYNew);
+
+	  // меняем startX, startY и startOffset
+	  this._startCameraOffset = this.camera.getOffset();
+	  this.startMouseX = getMouseX(event);
+	  this.startMouseY = getMouseY(event);
     } else {
 
       // calculate change in mouse position