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Leg_3jnt_01 - rotation 360 when blending with "leg_fullIK" attribute

Bug
#1

Hello Guys,

Sometimes when you set a pose to the 3jnt leg, and playing with the ‘Full 3 bones IK’ attribute,
the ‘legBack_L0_roll_ctl’ take a rotation of 180 with a blend value of 0.5

Apparently, the problem appears only on the left side and it depends on the bind pose.
Unless I’m mistaken, the solution seems to be to make a world match between these 2 groups:
‘legBack_L0_ik2B_A_ref’ & ‘legBack_L0_ik2B_B_ref’.

It’s not a blocking problem, we just need to add a small ‘post custom step’ procedure.
I hope this will help.

Best,
Mika

Leg_3jnt_01 knee flips when I Duplicate sym
#2

Sorry I didn’t do enough tests.
Apparently, it’s random at the rig build, it can happen on the right or on the left.

And perhaps the simplest solution is to pass the parent constraint on this group ‘legBack_L0_ik2B_blend’ to interpolation type: “shortest”.

1 Like
#3

Hello @MikaFr

Can you check if the behaviour change if you set the solver to rotation plane?
image

I remember Maya solves the IK spring in a random way each time. (and this is a Maya “feature”) I did add a checker but it may fail depending of the scale of your rig, because have a round precision
image

#4

Hello Miquel,

Yes I have the same issue with the ‘Rotation Plane’ solver.

I you want to see / reproduce the issue, you can take a look to the right ‘backLeg’ of your quadruped template.
Just move up the IK controller and drag smoothly the ‘leg_fullIK’ attribute (CTRL + middle mouse button + drag)
Just to be clear, I’m not talking about the leg roll functionality, but I’m talking about the controller of the last element of the leg. The controller with ‘roll’ in his name.

Thanks for your reply,
Mika

#5

Hi @MikaFr

I will check this ASAP. Thanks

#6

Resurrecting… just wanted to quickly note that this issue still exists and MikaFr’s solution of setting the interpolation type of the parent constraints to ‘shortest’ was a quick fix for us as well. Thanks!