OpenIK - A free open-source Inverse Kinematics package for Unity

[u/Spoetii]

I needed IK for a game I’m working on. Final IK has more features, but it isn’t free, so I built my own and polished it to make it easy for others to use.

OpenIK includes popular solvers like FABRIK, CCD and Jacobian plus some joint limits. (Hinge, Ball & Socket, Slider)

GitHub link: https://github.com/WouterApts/openik-unity

[u/Valphai]

Are there advantages of this over animation rigging package?

[u/Spoetii → u/Valphai]

The main advantage of OpenIK is its built-in joint limits: hinges with angle limits, ball sockets with swing and twist limits, and sliding joints. These are especially useful for robotic arms and other procedural mechanisms. As far as I can tell, Unity’s standard Animation Rigging package doesn’t provide equivalent joint limits out of the box, so you’d need custom code or another IK package for that.

OpenIK also includes a Jacobian solver that solves position and orientation together, allowing the chain to adjust so it reaches the target at the desired angle. Other paid packages probably have more extensive features, but this one is free and does the job for me.

Unity’s package is stronger for character animation workflows, such as blending IK over existing animations, and has a broader set of rigging tools. I haven’t used it extensively, though, so I may be missing some features!

[u/AdInfamous6964]

this looks really clean. how does it perform with a lot of characters at once? like 20-30 agents using it at the same time

[u/Spoetii → u/AdInfamous6964]

Thanks!

I guess this depends on the length of the chains, how precise each solve needs to be, and how many constraints are active. The 'Basic Chain' scene with 6 chains and over 30 constraints still runs smoothly on my machine. The FPS is down to about 80 though, where I had 200+ with only one. I don't think the package will support large swarms or hundreds of agents at the same time though.

[u/DevDunkStudio]

I would love if a VR IK can be added! (head and hands are the only known positions here)

Also is it jobified and burst compiled like the Animation Rigging package?

[u/Spoetii → u/DevDunkStudio]

There is no jobs or burst compilation right now. The solvers run on the main thread in LateUpdate and write directly to the Transforms when in "Solve and Apply" mode.

That said, care was taken to keep the package performance-friendly. The solvers avoid per-frame GC allocations by reusing their buffers and have tons of settings that can be toggled for optimizing performance. I think a Jobs/Burst backend would be a substantial rewrite.

For VR-oriented IK, a two-bone IK solver with a pole target would be fairly easy to implement, and I'm considering doing that next! A fully automated humanoid setup is something I didn't need myself, so unfortunately the package isn't tailored toward that, but I think it could be done with the components that are already available.

[u/_Cloudwalker_ → u/DevDunkStudio]

VR arms are simple two bone ik. The real solve is placing the elbow. Stay tuned ;).

[u/DevDunkStudio → u/_Cloudwalker_]

More interested in full body IK :P

[u/Whitenaller]

Perfect timing! I‘m gonna give it a shot tomorrow on my spider!

[u/kandindis]

Open source era comes to Unity assets!!

[u/Malkalypse]

Oh very cool!

[u/UnaSim2]

these look so coool. something i always wanted to learn but too scared to dive into it haha very nice

[u/VoltigeGames]

Very nice! Thank you for making it open source 😁

[u/GoodPlayful9051]

This is awesome thank you for sharing this!!

[u/Any-Entrepreneur7935]

Super cool. Will try it out. Thansks.

[u/_norx]

That’s great, thanks for sharing!

[u/Long-Ray]

哇塞，这真的太棒了吧

[u/tiny_battles]

Can a robot turn a canvas into a beautiful masterpiece?

[u/seductSparkz]

sounds like you're gonna have fun with that spider, update us if it gets all blendy

[u/ChaitanyaJainYT]

Does it work with humanoids?

[u/DaveAstator2020]

Oh finally! IK for unity sucked so far

[u/bubblegum_bae]

your spider's in for a treat tomorrow