The team at Unity have partnered with Microsoft-owned Havok to update their game engine with two new physics systems: one new default option and an additional "high-end" option backed by Havok's proprietary physics engine.

Announced today at GDC 2019, the new default Unity physics system will be open-source and available to all, while Unity's freshly-added Havok physics system will be proprietary and available to devs willing to pay for the privilege, though how much you'll pay is yet unclear.

This physics revamp is part of an ongoing effort to transition Unity's game engine to a data-oriented technology stack, which (to vastly oversimplify) aims to make the engine more efficient by cutting down how often it has to pull data from memory.

The company is quick to promise that devs who are currently making a game with Unity will have options to convert their work over to one of the new physics systems, or to keep working on their game without needing to upgrade.

"There will be no impact on game developers in the middle of building their game with existing physics solutions as these new solutions are for DOTS-based projects," Unity VP Andrew Bowell told Gamasutra via email.

"If developers would like to transition their projects to the DOTS framework, we have converters and upgrade paths in place to migrate existing physics content. If you are building a new project on the DOTS framework, the new Unity Physics or Havok Physics integrations will be the supported options."

Devs interested in the new Unity physics system should know that it's stateless, to complement the engine's shift to DOTS. Again, the idea is to make it more efficient by cutting down how often it has to pull data from memory, and according to Bowell, devs should see performance improvements in the new physics system.

"The new Unity Physics is a stateless design. which means that rather than rely on caching, we can use the efficiencies from DOTS to give developers a much simpler physics framework to tweak and modify," wrote Bowell.

By comparison, "if you have a team that has experience with Havok Physics or your use-cases are pushing on complex and high-fidelity physics requirements, the caching system of Havok Physics can offer better stability and performance," according to Bowell.

"On the tooling side, we’ve focused on streamlining the authoring side of things so you can build your physics content once and then swap the physics backend between Unity Physics or Havok Physics," he continued. "This is achieved by having a single data representation model of the editor data that is then converted into ECS data and shared between the two physics simulation backends."

Devs curious to learn more should check out the Unity website.