Update app.py

app.py

@@ -618,7 +618,7 @@ async(p, d, n)=>{
     if(objectUrl) {
         window.URL.revokeObjectURL(objectUrl);
     }
-    var serializedScene = BABYLON.SceneSerializer.Serialize(scene);
+    var serializedScene = BABYLON.SceneSerializer.SerializeMesh(scene);
     var strMesh = JSON.stringify(serializedScene);
     if (filename.toLowerCase().lastIndexOf(".babylon") !== filename.length - 8 || filename.length < 9){
         filename += ".babylon";
@@ -637,6 +637,20 @@ async(p, d, n)=>{
       if (BABYLON && BABYLON.Engine.LastCreatedScene) {
         BABYLON.Engine.LastCreatedScene.onAfterRenderObservable.add(function() { //onDataLoadedObservable
 
+          var then = new Date().getTime();
+          var now, delta;
+          const interval = 1000 / 25;
+          const tolerance = 0.1;
+          BABYLON.Engine.LastCreatedScene.getEngine().stopRenderLoop();
+          BABYLON.Engine.LastCreatedScene.getEngine().runRenderLoop(function () {
+            now = new Date().getTime();
+            delta = now - then;
+            then = now - (delta % interval);
+            if (delta >= interval - tolerance) {
+                BABYLON.Engine.LastCreatedScene.render();
+            }
+          });
+          
           var bg = JSON.parse(document.getElementById("bgcolor").getElementsByTagName("textarea")[0].value);
           BABYLON.Engine.LastCreatedScene.getEngine().setHardwareScalingLevel(1.0);
           for (var i=0; i<bg.length; i++) {