At SIGGRAPH 2022, Unity unveiled a new real-time demo titled Lion, which runs at 4K resolution, 30 frames per second on PlayStation 5 hardware. It was created with the following artist tools: Wētā Digital, SpeedTree, Ziva, SyncSketch, and of course, Unity Editor.
Clearly, the most impressive aspect of the Lion demo is the felines' fur rendering, made with Wētā Digital's new Wig hair and fur tool. Unity Technical Artist Sara Hansen explained:
Wig is a different way of working – it’s actually the fastest grooming tool that I’ve ever used. A high-quality hero groom – which would take me several months in another grooming package – is much faster to create in Wig. It takes just a couple of weeks, and some grooms go from weeks to create in other tools to only one or few days in Wig, and at far better quality levels and with greater artist controllability… Even when you have to react to detailed art direction feedback notes, like adjusting a specific strand from a reference shot, it’s easy to author in Wig.
That's the tool, but Unity had to be updated to enable the rendering of millions of individual fur strands, all moving independently.
One set of improvements includes a new GPU-driven clustered hair simulation that enables millions of hair strands to react dynamically in real-time, part of the new Hair System released on Unity’s GitHub. This approach builds on the hair simulation used for the incredible Digital Human showcase, Enemies, and expands the method to handle several orders of magnitude more hair strands efficiently on GPU.
For hair and fur rendering, the graphics developers at Unity designed a set of improvements to a GPU tile-based software rasterization algorithm in HDRP, with significant optimization to render several million unique hair strands. This method achieved smooth visuals with analytic anti-aliasing with compute-sorted order independent transparency for hair strands and improved advanced physically-based hair lighting models for film-quality hair strand rendering.
Unity said that these hair/fur simulation and rendering improvements will be released to the public with the 2023.1 Tech Stream.