Merge pull request #6968 from ahocevar/spin-animation

Shortest arc rotation animation improvements and upgrade notes

changelog/upgrade-notes.md

@@ -2,6 +2,26 @@
 
 ### Next release
 
+#### `ol.animate` now takes the shortest arc for rotation animation
+
+Usually rotation animations should animate along the shortest arc. There are rare occasions where a spinning animation effect is desired. So if you previously had something like
+```js
+map.getView().animate({
+  rotation: 2 * Math.PI,
+  duration: 2000
+});
+```
+we recommend to split the animation into two parts and use different easing functions. The code below results in the same effect as the snippet above did with previous versions:
+```js
+map.getView().animate({
+  rotation: Math.PI,
+  easing: ol.easing.easeIn
+}, {
+  rotation: 2 * Math.PI,
+  easing: ol.easing.easeOut
+});
+```
+
 ### v4.2.0
 
 #### Return values of two `ol.style.RegularShape` getters have changed

examples/animation.js

@@ -1,5 +1,6 @@
 goog.require('ol.Map');
 goog.require('ol.View');
+goog.require('ol.easing');
 goog.require('ol.layer.Tile');
 goog.require('ol.proj');
 goog.require('ol.source.OSM');
@@ -73,9 +74,16 @@ onClick('rotate-right', function() {
 });
 
 onClick('rotate-around-rome', function() {
+  // Rotation animation takes the shortest arc, so animate in two parts
+  var rotation = view.getRotation();
   view.animate({
-    rotation: view.getRotation() + 2 * Math.PI,
-    anchor: rome
+    rotation: rotation + Math.PI,
+    anchor: rome,
+    easing: ol.easing.easeIn
+  }, {
+    rotation: rotation + 2 * Math.PI,
+    anchor: rome,
+    easing: ol.easing.easeOut
   });
 });
 
@@ -103,10 +111,19 @@ onClick('bounce-to-istanbul', function() {
 });
 
 onClick('spin-to-rome', function() {
+  // Rotation animation takes the shortest arc, so animate in two parts
+  var center = view.getCenter();
   view.animate({
+    center: [
+      center[0] + (rome[0] - center[0]) / 2,
+      center[1] + (rome[1] - center[1]) / 2
+    ],
+    rotation: Math.PI,
+    easing: ol.easing.easeIn
+  }, {
     center: rome,
     rotation: 2 * Math.PI,
-    duration: 2000
+    easing: ol.easing.easeOut
   });
 });
 

src/ol/view.js

@@ -296,9 +296,7 @@ ol.View.prototype.animate = function(var_args) {
 
     if (options.rotation !== undefined) {
       animation.sourceRotation = rotation;
-      var delta =
-          ol.math.modulo(options.rotation - rotation + Math.PI, 2 * Math.PI) -
-          Math.PI;
+      var delta = ol.math.modulo(options.rotation - rotation + Math.PI, 2 * Math.PI) - Math.PI;
       animation.targetRotation = rotation + delta;
       rotation = animation.targetRotation;
     }
@@ -399,7 +397,7 @@ ol.View.prototype.updateAnimations_ = function() {
       }
       if (animation.sourceRotation !== undefined && animation.targetRotation !== undefined) {
         var rotation = progress === 1 ?
-          animation.targetRotation :
+          ol.math.modulo(animation.targetRotation + Math.PI, 2 * Math.PI) - Math.PI :
           animation.sourceRotation + progress * (animation.targetRotation - animation.sourceRotation);
         if (animation.anchor) {
           this.set(ol.ViewProperty.CENTER,

test/spec/ol/view.test.js

@@ -494,7 +494,7 @@ describe('ol.View', function() {
       });
     });
 
-    it('takes the shortest angle to the target rotation', function(done) {
+    it('takes the shortest arc to the target rotation', function(done) {
       var view = new ol.View({
         center: [0, 0],
         zoom: 0,
@@ -509,6 +509,21 @@ describe('ol.View', function() {
       });
     });
 
+    it('normalizes rotation to angles between -180 and 180 degrees after the anmiation', function(done) {
+      var view = new ol.View({
+        center: [0, 0],
+        zoom: 0,
+        rotation: Math.PI / 180 * 1
+      });
+      view.animate({
+        rotation: Math.PI / 180 * -181,
+        duration: 0
+      }, function() {
+        expect(view.getRotation()).to.roughlyEqual(Math.PI / 180 * 179, 1e-12);
+        done();
+      });
+    });
+
     it('calls a callback when animation completes', function(done) {
       var view = new ol.View({
         center: [0, 0],