Obi Rope 6.0: What’s new

Obi Rope 6.0 gets a complete revamp of the collision detection system, a new substepping scheme, and improvements to several core constraints. Also, and as always, bug fixes :).

Surface collisions

Obi is a particle-based engine. This means particles are the basic building block for object dynamics and collision detection. However, particles aren’t a particularly good representation of many real-world objects, and this is painfully obvious when dealing with collision detection:

Enter surface collisions:

Surface collisions work by using simplices (lines, triangles) instead of particles. This lets you use far fewer, smaller particles, which results not only in more robust but also better performant simulation in many cases.

You can read more about surface collisions in the manual, and  see them in action in this video:

Predictive constraint projection

In Obi 5.X, it was necessary to substep Unity’s own physics engine in sync with Obi (by enabling “substep Unity physics”) when using substepping together with rigidbodies. This meant updating all physics in your scene multiple times (once per substep), which severely limited real-world use cases. Not anymore.

Obi 6.0 extrapolates rigidbody position/rotation to the end of the entire step, solves positional constraints there, and interpolates the required delta corrections / impulses back in time to the current substep. This ensures stability even when updating Obi and Unity at different time steps.

This may sound complex and technical, but it boils down to two very simple things:

  • The “substep Unity physics” checkbox in updaters is gone. No longer needed.
  • Orders of magnitude faster simulation in complex scenes with more than 1 substep.

Constraint plasticity

Bend and twist constraints now support plasticity, which to date was only supported by shape matching constraints (softbodies). Plasticity is a physical effect that causes materials to be permanently deformed as a result of external forces.

This is what happens when you bend a metal rod, for instance:

Or when you flex your elbow, and the sleeve “remembers” wrinkles:

The initial release of Obi 6 focuses primarily on cloth and ropes, but we have some improvements for rigidbodies and fluid that will be rolled out in the 6.X development cycle.

As it usually is the case with Obi updates, updating to 6.0 is completely free. If you’re new to Obi, the price tag is also the same as it was for 5.X (and 4.X, and 3.X).

Hope you find it useful 🙂

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