Man, it’s just one error after another 
Runtime/CoreUObject/Public/UObject\Class.h(2354): Assertion failed: Class
ConstructObject called with a NULL class object
C:\UE-Master\Engine\Source\Runtime\Core\Private\Misc\OutputDevice.cpp(176): Fatal error:
Assertion failed: Class [File:Runtime/CoreUObject/Public/UObject\Class.h] [Line: 2354]
ConstructObject called with a NULL class object
Stack:
[Callstack] 0x00000000
69
This is what popped up in the scrollbox at the bottom of the html page.
Hmmm, I’m just installing XAMPP now, I haven’t seen any .data.js or .data files before, any idea how I get it to create them?
See comments below about running a local server stack. I was getting the exact same error. Also make sure that the .data.js file was created and .data.
the .data and .data.js should be created via the unreal frontend. This probably explains why your getting the error. Make sure your Emscripten environment is set up correctly. (Another issue I had was .py files were not associated with python, so a particular command during packaging was failing silently as it was trying to run the .py file by itself)
Hmmm, I thought I’d set up Emscripten properly. Do I need to build it from the source rather than installing the NSIS version?
I’ve set up the environment variables, .emscripten paths, and set .py’s to always open with the python.exe in the emscripten directory… am I missing something else?
I’m using the NSIS version, so no you dont have to build emscripten from source. Can you upload a copy of the log from frontend? See if I can identify any issues.
Yeah dont worry I know the feeling.
Okay looks like your having the exact same problem I was having. Even though .py files are set to open automatically with python it does not seem to be passing the args over correctly.
I fixed this by opening HTML5Platform.Automation.cs (Under Programs/Automation in VS). and going to Line 36 and changing the string to:
/c python {0} {1} --preload . --pre-run --js-output={1}.js
Then doing a rebuild in Frontend, hopefully the SwingNinja.data and SwingNinja.data.js appear correctly.
Sure, here it is.
Thanks for helping out Ehamloptiran! It’s kinda dumb since it’s not even a fully developed feature, but I’d really like to get it working 
It worked! Nice work, thanks man!
Appalling framerate, but that’s probably mostly my machine. Thanks for all the help!
Glad to hear its working
Using the master branch and the content from the lastest preview I get quite some compile errors when compiling the engine in Development for HTML5.
Here is the list of errors:
It seams that the required zip files do not match the one the engine expects for the phys asset error, but CopySceneAlpha in HTML is called without arguments while its declared with one (a scene view in this case).
Cheers,
Moss
This is expected. When developing from master (which mirrors our main development branch) the required binary zip files will quickly become out of date. You may find that you need to build tools such as CrashReporterClient, ShaderCompileWorker, UnrealHeaderTool, and UnrealBuildTool before you can properly compile the build.
The main branch also provides no guarantee of stability. You may find that you pull latest and that it won’t compile – this may well be the case for us internally for that given head position. You can try fixing the compile errors yourself or wait a while and pull again and hopefully the issue has been fixed internally and replicated its way to GitHub master.
Thank for the response Ben, I was just curios if I picked the wrong zip files 
So far this was a huge help. However when I try to build I get this Error:
Program.Main: ERROR: Failed to load script DLL: E:\UnrealEngine4\UnrealEngine-4.2.0-preview\UnrealEngine-4.2.0-preview\Engine\Binaries\DotNET\AutomationScripts\Win.Automation.dll: Could not load file or assembly ‘Win.Automation, Version=4.0.0.0, Culture=neutral, PublicKeyToken=null’ or one of its dependencies. Operation is not supported. (Exception from HRESULT: 0x80131515)
The dll is where it belongs, I tried to build the AutomationTool, the AutomationToolLauncher and the HTML5.Auotmation again. Is this something with the current master branch or was there something I missed?
Thanks!
Hi guys, I get as far as having a html file, but when opened in a 64bit (chromium or nightly) browser I get a blank page, that says “downloading” but nothing happens. Also, there is ONLY a html file an nothing else in the folder.
https://dl.dropboxusercontent.com/u/8833758/Blueprint/html5.jpg
I had the python problem as described by Ehamloptiran (.py files not associated with python, although the .emscripten file pointed to the correct folder). I tried to type in the exact string but VS gives me some weird errors when compiling (I am not a programmer). Maybe someone can give me the exact string?
https://dl.dropboxusercontent.com/u/8833758/Blueprint/vs.jpg
You have an extra " on your line
Thanks, which one is it, the middle one? (I am not a programmer)
I guess after that I have to build everything again, right?
I rebuild the html5.automation, the unreal frontend and ue4 with no changes… any ideas?
As per Ben Donatelli’s comment above:
Are you running the HTML file directly from disk (file:// in the URL) or are you hosting it via a local server stack (localhost/path/to/html/file)?
If you haven’t tried hosting via a local server stack, try using XAMPP. I found that running directly from disk caused some issues that cleared up when running through a proper web-server process.
I have tried it with XAMPP with not luck. Worth mentioning, that in the html5 folder there is just a single html file with only 7KB… that can’t be right.