Simple IK limitation(?)/bug
Issue #1439
invalid
Example: I’ve a lying character but I want to move the legs with the hips and the torso responding to it BUT I don’t want the torso to shift it’s location. For that I’m adding IK to the chest/torso controller with a empty. This works perfectly for Rigify but using it with simple IK it seems that it overwrites the IK on the feet because they move when I move the hip controller.
I’m not sure if that’s a bug or current limitation. If it’s a current limitation, could it be added to Simple IK?
Comments (7)
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repo owner
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This is not a bug. Simple IK doesn’t have IK for the spine but you can use auto-ik to pose if you connect bone chains. Of course with rigify you can do more things because it is a more advanced rig. To make simple IK be feature parity with rigify wouldn’t make any sense.
note for Thomas. We may add an option for simple IK to connect all bone chains to use auto-ik, also because it is perfectly compatible with daz poses. Then personally I don’t see any reason why “add custom shapes“ is a separate step. This is minor though since all the tools are there already.
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reporter
@Alessandro Padovani I tried auto IK but I can’t see how it helps fixating the upper chest so it doesn’t move when I move the hip bone?
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reporter
@Thomas Larsson Setting the chain length to 4 helped in terms of moving limbs, thanks. But you’re right, the bending behaviour of the back isn’t as nice as with rigify. I’m not a rigging expert but if I would want to modify simple IK in that regard, what’d be your suggestions?
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Of course not, auto-ik is a generic tool to pose a FK chain with IK, that’s supposed to be used with the simple IK rig. Again, if you need the rigify features then just go with it, in general you can’t make simple IK to behave like rigify.
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repo owner
No idea. I don’t know how to make spine IK work well, and you may have noticed that MHX doesn’t have it. You could try to dissect Rigify, but it has tons of mysterious bones and constraints and it is not easy to figure out how it does things.
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To make the IK constraint only affect the spine you should set the chain length to 4. But to make the spine bend in a nice way would take a lot more work than that. If you add an extra bone as the ik goal instead of the empty you don’t have to leave pose mode when posing.