Yeah, if that is the video I’m thinking about, then it doesn’t render outlines around things that are hidden behind walls.
To achieve the effect in question, perhaps the best way to do this is using a custom depth stencil, and a postprocess. This is also done in that video – you just need to configure it differently. You’ll want to render objects that need an outline into that pass. Then you’ll want to have a post-process that renders an outline where a neighboring pixel has custom stencil, but the depth test in the regular frambuffer fails.
Here’s a resource on custom depth stencil that collects a few other good links: Custom Depth and Custom Depth Stencil in UE4 - Superyateam Gamedev
Pay special attention to this example:
