Changes according to Deltakosh's review.

dist/preview release/babylon.max.js

@@ -16298,26 +16298,6 @@ var BABYLON;
             enumerable: true,
             configurable: true
         });
-        Object.defineProperty(Scene.prototype, "beforeStep", {
-            set: function (callback) {
-                if (this.onBeforeStepObservable) {
-                    this.onBeforeStepObservable.remove(this._onBeforeStepObserver);
-                }
-                this._onBeforeStepObserver = this.onBeforeStepObservable.add(callback);
-            },
-            enumerable: true,
-            configurable: true
-        });
-        Object.defineProperty(Scene.prototype, "afterStep", {
-            set: function (callback) {
-                if (this.onAfterStepObservable) {
-                    this.onAfterStepObservable.remove(this._onAfterStepObserver);
-                }
-                this._onAfterStepObserver = this.onAfterStepObservable.add(callback);
-            },
-            enumerable: true,
-            configurable: true
-        });
         Object.defineProperty(Scene.prototype, "unTranslatedPointer", {
             get: function () {
                 return new BABYLON.Vector2(this._unTranslatedPointerX, this._unTranslatedPointerY);
@@ -17193,18 +17173,6 @@ var BABYLON;
         Scene.prototype.unregisterAfterRender = function (func) {
             this.onAfterRenderObservable.removeCallback(func);
         };
-        Scene.prototype.registerBeforeStep = function (func) {
-            this.onBeforeStepObservable.add(func);
-        };
-        Scene.prototype.unregisterBeforeStep = function (func) {
-            this.onBeforeStepObservable.removeCallback(func);
-        };
-        Scene.prototype.registerAfterStep = function (func) {
-            this.onAfterStepObservable.add(func);
-        };
-        Scene.prototype.unregisterAfterStep = function (func) {
-            this.onAfterStepObservable.removeCallback(func);
-        };
         Scene.prototype._addPendingData = function (data) {
             this._pendingData.push(data);
         };
@@ -18295,7 +18263,10 @@ var BABYLON;
             }
             if (this._engine.isDeterministicLockStep()) {
                 var deltaTime = Math.max(Scene.MinDeltaTime, Math.min(this._engine.getDeltaTime(), Scene.MaxDeltaTime)) / 1000;
-                var defaultTimeStep = this._physicsEngine.getTimeStep();
+                var defaultTimeStep = (60.0 / 1000.0);
+                if (this._physicsEngine) {
+                    defaultTimeStep = this._physicsEngine.getTimeStep();
+                }
                 var maxSubSteps = this._engine.getLockstepMaxSteps();
                 this._timeAccumulator += deltaTime;
                 // compute the amount of fixed steps we should have taken since the last step

src/babylon.scene.ts

@@ -388,28 +388,12 @@
         */
         public onBeforeStepObservable = new Observable<Scene>();
 
-        private _onBeforeStepObserver: Observer<Scene>;
-        public set beforeStep(callback: (data:Scene, state: EventState) => void) {
-            if (this.onBeforeStepObservable) {
-                this.onBeforeStepObservable.remove(this._onBeforeStepObserver);
-            }
-            this._onBeforeStepObserver = this.onBeforeStepObservable.add(callback);
-        }
-
         /**
         * An event triggered after calculating deterministic simulation step
         * @type {BABYLON.Observable}
         */
         public onAfterStepObservable = new Observable<Scene>();
 
-        private _onAfterStepObserver: Observer<Scene>;
-        public set afterStep(callback: (data:Scene, state: EventState) => void) {
-            if (this.onAfterStepObservable) {
-                this.onAfterStepObservable.remove(this._onAfterStepObserver);
-            }
-            this._onAfterStepObserver = this.onAfterStepObservable.add(callback);
-        }
-
         /**
          * This Observable will be triggered for each stage of each renderingGroup of each rendered camera.
          * The RenderinGroupInfo class contains all the information about the context in which the observable is called
@@ -1657,22 +1641,6 @@
             this.onAfterRenderObservable.removeCallback(func);
         }
 
-        public registerBeforeStep(func: () => void): void {
-            this.onBeforeStepObservable.add(func);
-        }
-
-        public unregisterBeforeStep(func: () => void): void {
-            this.onBeforeStepObservable.removeCallback(func);
-        }
-
-        public registerAfterStep(func: () => void): void {
-            this.onAfterStepObservable.add(func);
-        }
-
-        public unregisterAfterStep(func: () => void): void {
-            this.onAfterStepObservable.removeCallback(func);
-        }
-
         public _addPendingData(data): void {
             this._pendingData.push(data);
         }
@@ -2984,7 +2952,12 @@
 
             if(this._engine.isDeterministicLockStep()){
               var deltaTime = Math.max(Scene.MinDeltaTime, Math.min(this._engine.getDeltaTime(), Scene.MaxDeltaTime)) / 1000;
-              var defaultTimeStep = this._physicsEngine.getTimeStep();
+
+              var defaultTimeStep = (60.0 / 1000.0);
+              if (this._physicsEngine) {
+                defaultTimeStep = this._physicsEngine.getTimeStep();
+              }
+
               var maxSubSteps = this._engine.getLockstepMaxSteps();
 
               this._timeAccumulator += deltaTime;