UNDERLIE: Mixed Reality Underworld

UNDERLIE: Mixed Reality Underworld (cover art)
A "Portal" doorway
Monster (Promo Image)
Skeleton Enemy (Promo Image)
A window to another world

The Dream

For decades, people have dreamed of a Virtual Reality where you're actually IN the game world.

Not thumbstick locomotion or gorilla-style--but a virtual world that you can freely walk around inside.

This "dream" is now possible for consumer VR... IF a game generates a virtual world in the shape of a player's home space.

I believe that "UNDERLIE: Mixed Reality Underworld," released in 2025, is the very first game to generate a full, textured game world based on the detailed Scene Mesh--which is a polygonal mesh captured during the Meta Quest's "Space Setup" process. And the game can connect multiple rooms!

How the Dream is Achieved

Allowing the player to feel comfortable navigating a large virtual environment requires subtle use of Mixed Reality techniques to give the player spatial awareness without overwhelming their perception of the virtual world.

UNDERLIE uses the Meta Depth API for dynamic occlusions, to help blend in just the right amount of "real world" passthrough to not overpower the virtual world. But it doesn't just use the standard Soft Occlusions--it uses a more "ghostly" modified version to blend things more subtly. This matches the "spooky, alternate dimension" theme of the game!

Another innovative technique that UNDERLIE uses is blending passthrough visibility based on the illumination of the virtual world. Lights in the game reveal the virtual world, whereas dark areas can reveal the real world in a spooky "night-vision" passthrough effect.

Powerful Mixed Reality, Casual Gameplay

UNDERLIE is simple to play, but hard to master. For this competition, I made the game simpler and easier!

You only need one button on one hand to play. Just pull the trigger and blast the enemies. Reloads now happen automatically and now the gun never runs out of ammo! Some menus are also trimmed so the game is quicker to jump into.

Technology Overhaul

For this competition, I knew I wanted to take the tech to the next level.

Prior to this competition, UNDERLIE only allowed one "portal doorway" out of the home into a purely virtual area. I did an overhaul of the "portal hole" system with a new technique to allow more than one open hole. Using Unreal Engine, a major challenge in building that system is allowing dynamic occlusions to work in front of the "holes" in the room. The new system involves a low-res Scene Capture to capture the depth of invisible "hole" meshes combined with modified occlusion shaders. Now in the game, there can be a new "window" with an environment outside where enemies can spawn.

This update also brings new, richer environmental detail in the form of "outgrowths" spawned around the player's home environment. See the gunk dangling from the ceiling!

A New Era of VR has Arrived

From a technical standpoint--with it's focus on graphical fidelity and never-before-seen mixed reality techniques--I believe that UNDERLIE is one of the most immersive mixed reality games on the market.

With its use of the detailed Scene Mesh and the use of passthrough effects to help spatially orient players, I believe that UNDERLIE fulfills the long-awaited dream where players can freely walk around large virtual spaces from the comfort of their home.