OrbitControls: fix zoom-changed detection (#27834)

* OrbitControls: fix zoom-changed detection

* OrbitControls: clean-up

examples/jsm/controls/OrbitControls.js

@@ -261,6 +261,7 @@ class OrbitControls extends EventDispatcher {
 				scope.target.clampLength( scope.minTargetRadius, scope.maxTargetRadius );
 				scope.target.add( scope.cursor );
 
+				let zoomChanged = false;
 				// adjust the camera position based on zoom only if we're not zooming to the cursor or if it's an ortho camera
 				// we adjust zoom later in these cases
 				if ( scope.zoomToCursor && performCursorZoom || scope.object.isOrthographicCamera ) {
@@ -269,7 +270,9 @@ class OrbitControls extends EventDispatcher {
 
 				} else {
 
+					const prevRadius = spherical.radius;
 					spherical.radius = clampDistance( spherical.radius * scale );
+					zoomChanged = prevRadius != spherical.radius;
 
 				}
 
@@ -298,7 +301,6 @@ class OrbitControls extends EventDispatcher {
 				}
 
 				// adjust camera position
-				let zoomChanged = false;
 				if ( scope.zoomToCursor && performCursorZoom ) {
 
 					let newRadius = null;
@@ -313,15 +315,19 @@ class OrbitControls extends EventDispatcher {
 						scope.object.position.addScaledVector( dollyDirection, radiusDelta );
 						scope.object.updateMatrixWorld();
 
+						zoomChanged = !! radiusDelta;
+
 					} else if ( scope.object.isOrthographicCamera ) {
 
 						// adjust the ortho camera position based on zoom changes
 						const mouseBefore = new Vector3( mouse.x, mouse.y, 0 );
 						mouseBefore.unproject( scope.object );
 
+						const prevZoom = scope.object.zoom;
 						scope.object.zoom = Math.max( scope.minZoom, Math.min( scope.maxZoom, scope.object.zoom / scale ) );
 						scope.object.updateProjectionMatrix();
-						zoomChanged = true;
+
+						zoomChanged = prevZoom !== scope.object.zoom;
 
 						const mouseAfter = new Vector3( mouse.x, mouse.y, 0 );
 						mouseAfter.unproject( scope.object );
@@ -374,12 +380,13 @@ class OrbitControls extends EventDispatcher {
 
 				} else if ( scope.object.isOrthographicCamera ) {
 
-					zoomChanged = scale !== 1;
+					const prevZoom = scope.object.zoom;
+					scope.object.zoom = Math.max( scope.minZoom, Math.min( scope.maxZoom, scope.object.zoom / scale ) );
 
-					if ( zoomChanged ) {
+					if ( prevZoom !== scope.object.zoom ) {
 
-						scope.object.zoom = Math.max( scope.minZoom, Math.min( scope.maxZoom, scope.object.zoom / scale ) );
 						scope.object.updateProjectionMatrix();
+						zoomChanged = true;
 
 					}