segross
commented
3 years ago Hi @Zenahr, and thank you.
I'll try but I'm not sure how much advise I can offer without knowing Ultralight framework.
I'm afraid that there are no specific links that I can give you. I was thinking that https://wiki.unrealengine.com/An_Introduction_to_UE4_Plugins, but it seems gone. Other than the usual: official documentation (wherever available), API references, browsing through the engine's code and Epic's videos, there are some nice blogs about UE. I usually find something when searching for a specific topic.
However, I'll write that and you can as if something is not clear:
1) Making the plugin. I've watched Epic's video about plugin development but I cannot find it anymore (there are other ones, though). This however seems nice at the first sight: https://www.benteveo.kiwi/blog/advanced-unreal-engine-tutorial-part-1 Other than that, I'd start by creating an empty plugin in the editor. There are a few different templates, including plugins with dynamically loaded libraries. That was quite useful as the first step and to see what is possible, but in general:
- You need to implement the module (pretty sure it doesn't need to be public like in my plugin, and I might also make it private).
- You use Build.cs to set different settings, symbols, and public and private include paths and dependencies. The idea is that public ones are available outside of your module.
- You can use uplugin to set module name, type, and loading phase. Plugin can have multiple modules.
- If you want your plugin working correctly with Unreal Engine, you will need to make sure that it plays nicely with hot-reloading. Check at module startup/shutdown functions and module reloading where necessary. It might be the case that it can be done better than in my plugin, especially if you use
UObjects.
2) Slate. You will need to work with Slate, so I'd check that. I only found some simple "Hello, Slate" tutorial but it was enough. Even though you implement a different UI solution, chances are that it needs to work with Slate here and there.
3) Widget Reflector is a great way to explore how things are done with Slate.
5) Input. I had to create a widget that can handle input. I didn't find a better solution, and I know that guys implementing Coherent UI used something that sounded similar. You may need to make sure that it handles correctly input captures. There is a bit of that in SImGuiWidget. Since I use my solution primarily for debugging I wanted to be able to cover the whole screen and block input from going to the game. This is not always desirable (probably not for you), so you might need to find the best behavior that works for you.
5) Rendering. Again, you can check SImGuiWidget for that part. The FSlateDrawElement API was easy enough but it has one issue (which I noticed and didn't yet fix). Basically, ideally, you would bind vertex and index buffers when processing draw lists but with FSlateDrawElement you copy both buffers with every call to FSlateDrawElement::MakeCustomVerts. This can result in artificially bloating render data when multiple lists use the same part of vertex buffer. Perhaps if you made your own shader or used RHI it would be avoidable, but I'm not that fluent with graphics. Or maybe there is something in the FSlateDrawElement that I didn't find. However, for a first iteration, you could just ignore it.
6) The ImGui uses one global context which had a few implications for me. Depending on how is done, you might have a different situation.
- In the editor I need one context per PIE world, so each game can have its own debug. There is a bit of managing that, which could be avoidable if each Ultralight widget had its own... whatever it needs ;) That could probably also made hot-reloading easier.
- Also, since I want it for debugging, I want to be able to make ImGui calls from any place in the game. This is why I have debug delegates and why I switch context before world update. But if you are doing a solution purely for UI, you can probably avoid that complexity and only draw controls from within your widget update. I am actually thinking about implementing a side feature like this, which would be for creating "standalone" UI widgets.
Zenahr
Hi @segross!
Great work that you've done with UnreallImGui! I'm currently contemplating on creating Unreal Engine bindings for the HTML5 rendering engine https://ultralig.ht/ Reason being that this would allow web developers to create user interfaces using web technologies. This would simplify and streamline a lot of UI work I believe and at least for me personally, this would make it much easier and less error prone to work with dynamic data (e. g. a list for servers that users could join)
I'm a novice C++ programmer though and the task seems daunting to me. I've looked at some of your commits on UnrealImGui but I personally wouldn't know where to start on my project.
So I was thinking if you could give me your insights into how much work and how complex it is to create something like that based on your experience with UnrealImGui.
And perhaps you could point me towards helpful documentation regarding such an undertaking. I myself have to yet find useful examples online besides your code repository which I already use for reference.