Stingray is a 3D game engine by Autodesk that you can get it as part of a subscription, or free when you get Autodesk Maya LT.
The engine is capable of producing stunning visuals for games and interactive visualizations, and can receive data directly from Maya LT. Actually, I covered a previous version of this engine in another article which you can read here.
If you are using Maya LT, you already have Stingray, so in case you are not using it, you should take a look at it. When you launch Stingray, you are greeted with a "Welcome" window similar to that in Unity or the UE4 Launcher. This window lets you open a new project, create a project, or download a project from the internet. UE4 users will find this familiar since that engine allows you to start a project from scratch or use one of the prebuilt templates to create a game (character, vehicle, VR, etc.).
If you saw my previous article about the engine, then you've noticed Stingray is capable of producing amazing visuals, and I'd say Stingray rivals UE4 in the graphics department very easily. On top of that, the editor is very responsive and lean. Granted I haven't used UE4 in a long time (about 2 years), and I understand it runs smoother and more stable now, but using Stingray feels like Unity-levels of stability and smoothness.
However, my biggest interest was testing how Maya LT and Stingray work together. If you have used more than one Autodesk application before, then you are familiar with the way Maya is able to send data to Mudbox, MotionBuilder, etc. Functionality is pretty much the same here. You can send a model or a full scene from Maya directly into Stingray. The only crucial difference is that you need to have Stingray open before doing it (unlike other cases where the target application will launch as soon as you use the "Send to..." command inside Maya).
In my Maya LT article, I mentioned how Maya LT is able to send assets to Unity (as well as use a universal "Game Exporter" command). In those cases, Maya pretty much exports the .FBX file to the target application. However, in this case, Stingray opens a pop-up with some import settings. Another difference is that Maya LT and Stingray keep a "live connection" like the one between other Autodesk applications. This means that, rather than re-exporting an asset after making some changes, you can simply click the "update" button at the bottom of the Maya interface and the asset inside Stingray will update automatically.
In Maya LT you can also create a Stingray PBS material, so you can create a custom material for Stingray directly into Maya (including color and textures). This material is fully editable with ShaderFX, so you can customize it to fit your needs. I think this is a nice touch over the other ShaderFX materials, since those materials are good for visualizing your assets inside Maya (especially since Maya LT uses a game-like viewport), but they cannot be exported to game engines.
However, it's not as widely used as other engines like Unity or UE4, which sets the stage like this: On one side, it looks like a very capable engine, because it has a pretty good rendering engine capable of producing some really good visuals, it uses a programming language that (as I understand) is easy to use, has a live connection from Maya LT, and offers a set of templates (similar to UE4) that can help you get started or get acquainted with the software.
On the other side, there aren't many (third party) learning resources for it, it doesn't have big communities behind it, and is not as widely used as Unity or UE4.
This leaves Stingray in a weird position, and I'd wish Autodesk took the time to give their engine a bigger push (especially since it's being bundled with Maya LT). However, I'd still recommend you give Stingray a try.
Relevant links: https://www.autodesk.com/products/stingray/overview