Plugins in UE4.19.2 won't build/can't install

Hi there,

Just trying to get Lightact working with UE4 and when I follow the instructions to rebuild the .dlls I get an error that it could not compile and to try building from the source.

In Visual Studio I get these errors:
‘Expected SpoutBPFunctionLibrary.h to be first header included.
Expected SoutModule.h to be first header included.’

I am using 4.19.2 and have downloaded the most recent github commits today. Can someone please help me with what is going wrong here? Up against a tight deadline today and was not expecting the installation to be this technical.

Additionally could you provide some instructions on how to add the necessary c++ classes to a blueprints project so that I can get the plugins working in that instead of a c++ project? Our project is in Blueprints.

Many thanks,


Thank you for posting to our Answerhub.

A few notes:

  • Installing additional UE plugins can sometimes be quite technical, unfortunately.
  • it seems that you’ve already ‘Added code’ to your blueprint project since you are mentioning Visual Studio. Am I correct? The procedure to add code to a blueprint project is simply to add an empty C++ class.
  • since you mentioned you’ve got a deadline today, allow me to point out that the Free version of Lightact (data stream to UE and all texture inputs and outputs) is watermarked. If you want to remove these watermarks, you’ll have to purchase at least Lightact One license. This comes with a USB dongle, which we will have to ship it to you and which, depending on your location, takes a few days unfortunately. I thought this is something you should have in mind, if you have a deadline today.
  • which Visual Studio are you using?

Hi meetya,

Thanks for getting back to me so quickly!

I’ve been following the youtube tutorial you guys put up so the project i’m trying to compile is just a test one for now. Our actual project is solely in blueprints, but thanks for letting me know all i have to do is create an empty c++ class in that project and move the plugins to the plugins folder. Is that correct?

Our progammer says he managed to get it to compile by making these changes to the Spout plugin files:

  • in Source/SpoutPlugin/Private/SpoutBPFunctionLibrary.cpp, I had to move the “include …/Public/SpoutBPFunctionLibrary.h” line to the top

  • in Source/SpoutPlugin/Private/SpoutModule.cpp I had to add #include "SpoutModule.h" to the top

I’m using Visual Studio 2017, with all the C++ stuff for games and Unreal engine enabled.

That’s all ok about the watermark, our deadline is just to confirm this is a workable solution for us today, and then we will buy the dongle and you can ship it as fast as possible to New York.

Many thanks,


That’s correct. UE has a pretty clear distinction between pure Blueprint projects and mixed projects (BP + Code). In order to convert a BP project to a ‘mixed’ one, the simplest way is just to add an empty C++ class.

That’s weird, but thanks for pointing it out! :+1: We’ll investigate, but if you need any additional help let me know.

What are you trying to do, in broadstrokes, with Lightact and Unreal, if you don’t mind me asking?



Ok cool. I’ve succesfully built the test project as of making those changes to the code, so next i’ll add an empty c++ class to our project and see if everything builds ok there.

Don’t mind you asking at all! The project is an art installation for an american gallery that involves projection mapping some live content from Unreal engine onto a glass sphere. We’re using a short throw projector with a convex mirror to throw onto the majority of the glass spheres surface and hoping to use the warping tools in Lightact to compensate for the spherical distortion and create a nicely perspectival image when seen from straight on. I was hoping we could accomplish this entirely in Unreal with lens distortion shaders, but that hasn’t been so succesful so Lightact looked like a nice and clean solution for us.

Many thanks,

1 Like

Sounds very exciting! Post some images here or, even better, to our Facebook group when you are done. :slight_smile:


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