Apex rig IK setup with 5 joints and limiting rotation

Forums Rigging Apex rig IK setup with 5 joints and limiting rotation

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Aderik: Member; 2 posts; Joined: Sept. 2019; Offline

Feb. 1, 2024 10:17 a.m.

I am learning the new Apex system and loving it but am struggling with creating an IK system for this mesh.

While I know how to do the basic IK system, I have not yet found/understood how to create an IK system with more joints and one that limits the rotation axis in the top two.

Does anyone know a way or has a suggestion on how this can be done with Apex?

Attachments:
apex_rig_arm.png (181.0 KB)


kodra: Member; 213 posts; Joined: June 2023; Offline

Feb. 1, 2024 7:25 p.m.

There is FBIK node. However rotation limit isn't supported yet. So nope. APEX is in beta, please lower your expectation.

Edited by kodra - Feb. 1, 2024 19:30:35


Fraenk: Member; 10 posts; Joined: March 2015; Offline

Feb. 2, 2024 7:25 a.m.

Why would you need more than 3 joints for the main-arm (which is the default ik-setup anyway) + using a fk-rotation for the manipulator? You could limit the rotations using clamp-nodes.


kodra: Member; 213 posts; Joined: June 2023; Offline

Feb. 2, 2024 7:58 a.m.

I mean you can do that, but >3 bone IK is the "standard" way to rig this kind of mechanical arm.

Or you can use KineFX, which has better FBIK support with rotation limits etc.

Or you can write your own FBIK in APEX. People are going to tell you APEX is a super flexible system where anything is possible. (plebs who are not able or willing to do this are simply not good enough for Houdini

)

Edited by kodra - Feb. 2, 2024 08:02:00


edward: Member; 7734 posts; Joined: July 2005; Offline

Feb. 2, 2024 8:53 a.m.

No worries, it's on the TODO list.


UtilitasArts: Member; 10 posts; Joined: April 2021; Online

Feb. 3, 2024 4:12 a.m.

I build a digitigrade IK leg yesterday (posted it on the discord server).
perhaps you can take a look at it to get some inspiration.

I'm pretty confident the same could be done to for more joints.

I am not sure yet how to do the limiting rotation part. I will take a look into limiting rotations today.

Edited by UtilitasArts - Feb. 3, 2024 04:13:19

Attachments:
ApexChickenLeg1.hiplc (224.1 KB)


UtilitasArts: Member; 10 posts; Joined: April 2021; Online

Feb. 3, 2024 9:46 a.m.

Here I have a file that locks a matrix from rotating further than specified rotation angles.

Attachments:
LockRotationsAimConstraint.hiplc (191.5 KB)


Aderik: Member; 2 posts; Joined: Sept. 2019; Offline

Feb. 5, 2024 5:05 a.m.

Thank you for all the responses, I will look into all of this!

kodra
Or you can write your own FBIK in APEX. People are going to tell you APEX is a super flexible system where anything is possible. (plebs who are not able or willing to do this are simply not good enough for Houdini )

I know my current limits, but I will try XD

Fraenk
Why would you need more than 3 joints for the main-arm (which is the default ik-setup anyway) + using a fk-rotation for the manipulator? You could limit the rotations using clamp-nodes.

Yes that was my plan B. It would just be easier for the animator if it can be moved by 1 ik controller.

Edited by Aderik - Feb. 5, 2024 05:07:47

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