4 Joint IK Handle With Rotation Constraint Not Allowing Full Range Of Motion

[audemy]

Hi All,

I've created a four-joint IK Handle on the xy-plane to solve the leg movement of a mech's leg; however, when I add a rotation constraint to the top joint (to prevent the top leg segment from clipping through the mech body) the second free joint doesn't compensate to make up for the rest of the range of motion.  The top segment hits the rotation limit and then the IK Handle will no longer pull the IK rig.  The Handle floats into space with the cursor while the rig stops moving.

Is there a way to set this up so that the second free joint will compensate for the rest of the range of movement?  Note that the second joint does rotate normally when used to move the IK Handle, for instance I can pull the Handle out to the maximum length of the leg and both joints open to 180° with the 3 segments of the leg in a line.

Here is an ascii picture with namings of the joints to assist in visualization:

|  mech_body      |

-------------------

        \ /

         0     - hip/top joint

        /|

       / |

      /  |

     0   |     - first free joint

     |   |

     |   | <-  - IK Handle connector indicator

     |   |

     0   |     - second free joint

      \  |

       \ |

        \|

         0     - bottom/foot joint

        /|\

       - - -   - foot

Let me know if you might be able to help.  Thanks for any help you can give.

Best,

Aud

[audemy]

I suppose the IK solver simply doesn't take into account any of the constraints placed on the joints and considers any end-of-motion edges reached by any of the joints to be hard limits for the whole IK chain instead of reaching those limits and then re-calculating the chain using only the unconstrained joints.

[sean.heasley]

Hi @audemy

What version of Maya are you working with?

Also, when you get a chance can you please zip and attach the scene file here or via dropbox/google drive or another file sharing program so I can take a look at it? If the file is under NDA or is confidential in anyway please send it to me in a private message instead of posting it here.

[audemy]

Hi Sean,

Thank you so much for your response.  I'm sorry, I realize now I have posted this in the wrong forum.  I have Maya LT 2018.3.

Here is an example of the issue, but perhaps the IK solvers are different between Maya and Maya LT?

You can see the Mech body and the leg and the foot.  The top joint has a limit on it to prevent clipping of the leg through the body and the foot cannot reach some of the possible locations when using the IK Handle.

Thanks for any help and I'll post this over in the Maya LT forum if that's best.

Thanks,

Aud

[audemy · Accepted solution]

Actually, @sean.heasley, upon further reflection I've realized that I'm wrong and the locations I was trying to put the foot are impossible for the stiff legs.  The solver looks to be working correctly.  Again, thank you for your offer of help.  I do appreciate you reaching out.

Best,

Aud

[sean.heasley]

Hi @audemy

No problem! Thanks for explaining what you did to solve this issue!