Minor Animation Cleanup

* Removed leftover inclusion of AnimationClipCreator.

- See #8677
  https://github.com/mrdoob/three.js/issues/8677#issuecomment-213629279

* Clarified AnimationMixer loop mode handling.

- See #8719

examples/webgl_morphtargets_horse.html

@@ -17,7 +17,6 @@
 
 		<script src="../build/three.js"></script>
 		<script src="js/libs/stats.min.js"></script>
-		<script src="js/AnimationClipCreator.js"></script>
 
 		<script>
 

examples/webgl_shading_physical.html

@@ -36,7 +36,6 @@
 		<script src="../build/three.js"></script>
 
 		<script src="js/controls/TrackballControls.js"></script>
-		<script src="js/AnimationClipCreator.js"></script>
 
 		<script src="js/Detector.js"></script>
 		<script src="js/libs/stats.min.js"></script>

src/animation/AnimationMixer.js

@@ -731,22 +731,19 @@ THREE.AnimationMixer._Action.prototype = {
 		var duration = this._clip.duration,
 
 			loop = this.loop,
-			loopCount = this._loopCount,
+			loopCount = this._loopCount;
 
-			pingPong = false;
+		if ( loop === THREE.LoopOnce ) {
 
-		switch ( loop ) {
+			if ( loopCount === -1 ) {
+				// just started
 
-			case THREE.LoopOnce:
+				this.loopCount = 0;
+				this._setEndings( true, true, false );
 
-				if ( loopCount === -1 ) {
-
-					// just started
-
-					this.loopCount = 0;
-					this._setEndings( true, true, false );
+			}
 
-				}
+			handle_stop: {
 
 				if ( time >= duration ) {
 
@@ -756,9 +753,7 @@ THREE.AnimationMixer._Action.prototype = {
 
 					time = 0;
 
-				} else break;
-
-				// reached the end
+				} else break handle_stop;
 
 				if ( this.clampWhenFinished ) this.pause = true;
 				else this.enabled = false;
@@ -768,68 +763,63 @@ THREE.AnimationMixer._Action.prototype = {
 					direction: deltaTime < 0 ? -1 : 1
 				} );
 
-				break;
-
-			case THREE.LoopPingPong:
-
-				pingPong = true;
+			}
 
-			case THREE.LoopRepeat:
+		} else { // repetitive Repeat or PingPong
 
-				if ( loopCount === -1 ) {
+			var pingPong = ( loop === THREE.LoopPingPong );
 
-					// just started
+			if ( loopCount === -1 ) {
+				// just started
 
-					if ( deltaTime > 0 ) {
+				if ( deltaTime >= 0 ) {
 
-						loopCount = 0;
+					loopCount = 0;
 
-						this._setEndings(
-								true, this.repetitions === 0, pingPong );
+					this._setEndings(
+							true, this.repetitions === 0, pingPong );
 
-					} else {
+				} else {
 
-						// when looping in reverse direction, the initial
-						// transition through zero counts as a repetition,
-						// so leave loopCount at -1
+					// when looping in reverse direction, the initial
+					// transition through zero counts as a repetition,
+					// so leave loopCount at -1
 
-						this._setEndings(
-								this.repetitions === 0, true, pingPong );
-
-					}
+					this._setEndings(
+							this.repetitions === 0, true, pingPong );
 
 				}
 
-				if ( time >= duration || time < 0 ) {
-
-					// wrap around
-
-					var loopDelta = Math.floor( time / duration ); // signed
-					time -= duration * loopDelta;
+			}
 
-					loopCount += Math.abs( loopDelta );
+			if ( time >= duration || time < 0 ) {
+				// wrap around
 
-					var pending = this.repetitions - loopCount;
+				var loopDelta = Math.floor( time / duration ); // signed
+				time -= duration * loopDelta;
 
-					if ( pending < 0 ) {
+				loopCount += Math.abs( loopDelta );
 
-						// stop (switch state, clamp time, fire event)
+				var pending = this.repetitions - loopCount;
 
-						if ( this.clampWhenFinished ) this.paused = true;
-						else this.enabled = false;
+				if ( pending < 0 ) {
+					// have to stop (switch state, clamp time, fire event)
 
-						time = deltaTime > 0 ? duration : 0;
+					if ( this.clampWhenFinished ) this.paused = true;
+					else this.enabled = false;
 
-						this._mixer.dispatchEvent( {
-							type: 'finished', action: this,
-							direction: deltaTime > 0 ? 1 : -1
-						} );
+					time = deltaTime > 0 ? duration : 0;
 
-						break;
+					this._mixer.dispatchEvent( {
+						type: 'finished', action: this,
+						direction: deltaTime > 0 ? 1 : -1
+					} );
 
-					} else if ( pending === 0 ) {
+				} else {
+					// keep running
 
-						// transition to last round
+					if ( pending === 0 ) {
+						// entering the last round
 
 						var atStart = deltaTime < 0;
 						this._setEndings( atStart, ! atStart, pingPong );
@@ -848,22 +838,19 @@ THREE.AnimationMixer._Action.prototype = {
 
 				}
 
-				if ( loop === THREE.LoopPingPong && ( loopCount & 1 ) === 1 ) {
-
-					// invert time for the "pong round"
-
-					this.time = time;
+			}
 
-					return duration - time;
+			if ( pingPong && ( loopCount & 1 ) === 1 ) {
+				// invert time for the "pong round"
 
-				}
+				this.time = time;
+				return duration - time;
 
-				break;
+			}
 
 		}
 
 		this.time = time;
-
 		return time;
 
 	},