The upcoming Unreal 5 engine has a new physics feature call Chaos. The system includes the following major features:

  • Rigid Body Dynamics
  • Rigid Body Animation Nodes and Cloth Physics
  • Destruction
  • Ragdoll Physics
  • Vehicles
  • Physics Fields
  • Fluid Simulation
  • Hair Simulation

The Chaos Physics system replaces the legacy physics system, and comes with significant improvements in performance. In addition, Chaos Physics comes with major new features, such as Asynchronous Physics simulation and networking, a robust destruction system, and Physics Fields.

This overview goes over the differences between the major features of Chaos and PhysX. With Unreal 4 most developers ended up using PhysX to support animation.

Cloth physics will make it easier to realistically animate characters in games. Chaos Cloth provides more accurate simulations by removing any hard limits for collision primitives per cloth mesh, up from a maximum of 32 primitives in the legacy system. This enables the user to determine the best setup for quality vs. performance.

Physical reactions to wind forces are also significantly improved to provide a more natural simulation. The wind simulation is more accurate than the legacy model, as it takes into consideration the affected surface area of the cloth mesh. Using this model allows the cloth mesh to continue interacting with its surroundings along with the effects of the wind.

Chaos Cloth provides increased control over the simulation results by exposing cloth parameters in an easy-to-use interface. The cloth Backstop Radius implementation is now more intuitive, allowing users to more easily author the mesh backstop to prevent clipping between the cloth mesh and mesh collision. This results in increased artistic control.

The Animation Drive system is more powerful and easier to set up than the legacy system. This system deforms a cloth mesh to match its parent animated skeletal mesh. In this system, values are normalized between 0 and 1, allowing for more intuitive controls. A damping algorithm has been added to provide a way to reduce the springiness between the animated cloth and the skeletal mesh.

Chaos Cloth parameters are now exposed to Blueprints for unprecedented control over the cloth simulation at runtime. Users can now modify simulation parameters based on gameplay conditions for specific use cases. For example, a character’s clothing can react differently when under water.

The work going into Unreal 5 is clearly very impressive. The early access is available now but it should be production ready in a few more months.