How Unity created Time Ghost, its beautiful Unity 6 tech demo
Unity has previewed Time Ghost, a tech demo showcasing the capabilities of Unity 6, the latest version of the game engine, including advances in lighting, hair, and large-scale environments.
The four-minute demo, which runs in real time on a GeForce RTX 4090 GPU, also uses a custom machine learning model for cloth deformation deployed via Unity’s Sentis AI framework.
The demo assets themselves will be released alongside Unity 6 when it ships next month, but below, you can discover how the demo was created.
Time Ghost was premiered during the keynote from Unity’s Unite 2024 conference. The section on the making of the demo starts at 00:48:30.
A real-time demo showcasing the new graphical capabilities of Unity 6
Time Ghost shows a soldier exploring a huge, seemingly empty landscape after mysteriously escaping what plays out like a steampunk version of trench warfare during World War I.
It showcases the capabilities of Unity 6, the upcoming long-term support version of the game engine, using features introduced in the Unity 6 Preview release earlier this year.
Unity 6’s Adaptive Probe Volumes system automated the placement of light probes, concentrating them in more complex areas of the scene like the foreground trench.
Lighting: Adaptive Probe Volumes and Scenario Blending
The early combat scenes show multiple animated characters moving through a detailed environment with multiple FX elements and volumetric fog, using 6-way lighting for the smoke.
For light baking, Unity’s Adaptive Probe Volumes system was used to optimize the placement of light probes, automatically placing probes more densely in complex areas of the scene like the trench than the surrounding plain.
The demo team created multiple Lighting Scenarios representing different times of day, blending between them to create transitions in time.
To improve render performance, the demo makes use of the GPU Resident Drawer, Unity 6’s “behind-the-curtain” system for processing scenes with a lot of instanced objects.
Although nearly 8.5 million pieces of vegetation are active in the scene at peak, ECS Imposters reduce the number of entities passed to the graphics system, improving performance.
Environment design: ECS helps process instanced vegetation
And Time Ghost does feature a lot of instanced objects: according to Unity, the full scene features more than 12 million instances of vegetation, including trees and grass.
The demo team used Houdini to scatter the 3D plants, exporting their basic properties to Unity as a point cloud.
The baking capabilities of Unity’s Entity Component System (ECS) were used to generate separate entities for each plant, and to create ‘Imposters’ representing clusters of plants that could be swapped in when displaying vegetation at a distance from the camera.
According to Unity, at maximum, nearly 8.5 million pieces of vegetation are active, but fewer than 0.5 million individual entities are passed to the graphics system, improving performance.
FX: Improvements to real-time hair and the VFX Graph
Time Ghost also makes use of advances in Unity’s real-time hair system, showcased on previous Unity tech demos like Enemies and Lion.
They aren’t discussed during the Unite 2024 keynote, but according to Unity, the new capabilities include “seamless rendering LOD, automatic LOD generation [and] volumetric wind”.
To enhance the realism of the early scenes in which characters are showered with earth thrown up from explosions, the demo also makes use of improved support for collisions in the VFX Graph, allowing chunks of debris to break apart on contact.
Sentis: custom AI model approximates cloth deformation from offline sims
According to Unity, the demo was developed in an unmodified version of Unity 6, but it also makes use of Sentis, Unity’s system for deploying custom AI models at runtime.
In the case of Time Ghost, it was used for cloth, with the demo team creating an AI model capable of running in real time that approximates the behavior of offline simulations.
Using “DCC tools” – they weren’t specified, but Marvelous Designer and Houdini were namechecked earlier in the presentation – the demo team created 2,000 frames of training data showing how clothing deformed as a character moved.
The character’s joint positions and the corresponding cloth deformations were then used to train the AI model, a process that “took about an hour on a desktop PC”.
The resulting model occupies 47MB of disk space, compared to 2.5GB of original training data, and generates deformations in 0.8ms per frame.
Release date and system requirements
The Time Ghost demo scenes will be released alongside Unity 6 itself, which is due to launch globally on 17 October 2024.
The current development release, the Unity 6 Preview, is compatible with Windows 10+, Ubuntu 20.04/22.04 Linux, and macOS 11.0+.
The demo itself runs in real time on a PC equipped with an Intel Core i9-14900K CPU and a NVIDIA GeForce RTX 4090 GPU.
You can find pricing details in this story on Unity cancelling its planned Runtime Fee.
Read more about Time Ghost on Unity’s website
Updated: Watch a recording of the session on the making of Time Ghost from Unite 2024