This video shows the performance improvements you can see when loading integrated mesh scene layers in Scene Viewer or JavaScript API. This scene is showing an integrated mesh scene layer of Yosemite National Park hosted on ArcGIS Online. The improved scene layer loading performance is part of the Scene Viewer December 2017 & Esri JavaScript 4.6 update.
Learn more, here: https://doc.arcgis.com/en/arcgis-online/get-started/get-started-with-scenes.htm