Been trying to get PBR materials to load on an STL but have been having problems. I decided to just start over and download the example project here: http://babylonjs-playground.com/#1GELZQ#7 However, when I run it (without any modification in multiple browsers) I get the error "TypeError: BABYLON.PBRMaterial is not a constructor" This is an official example so I don't know what I'd be doing wrong.