Instant physics is a lightweight animation tool, that adds pleasing, artist‑driven secondary motion to your existing animation; all without the bugginess, instability, or performance cost of traditional physics solvers.

With just one or two controls — a simple location or rotation offset — you can bring your animation to life. The system inherits and amplifies your base motion, keeping everything crisp, predictable, and intent‑driven. 

Edit as many bones as you want at once to instantly create swinging chains, wagging tails, fluttering accessories, and much more.

Instant Physics doesn’t just react to motion — it can also anticipate it, enabling you to create new procedural animations that traditional physics solvers can't achieve.

The addon is built for extremely fast iteration. Its simplicity is its strength: by skipping gravity, wind, and collision simulation, you can achieve results very quickly, without worrying about a playback performance hit.

tutorial and introduction here:

Mecha model used with permission from Pierrick Picaut and P2DESIGN S.A.S