Default chain length for ik constraint set to 2 bones
Every time you create a new ik constraint, the default chain length is set to 0, which means the ik constraint will use all bones. I would hasten to bet that this is hardly ever the use case people expect. More than 50% of the time when using IK, you are expecting either 1 or 2 bones to be affected.
I would request that the default chain length be changed to be 2 bones, so it's more useful and obvious for new users what it's doing.
4 Comments
I'm agree with Fweeb, I like 0 as default much more, but I think maybe can add one good way to solve this, like: select first bone as target bone, the second bone as length bone, and the third bone is the aim bone(witch to add IK constraint ), than press Shift+I, so not to set length, just select, and if you only select two bone, the length will not change, it's cool idea too : )
I keep swinging back and forth on this, trying to decide if it's a good idea. On one hand, applying an IK constraint to a fully connected bone chain can make a rig twist around in all kinds of unexpected and "exciting" ways. However, on the other side, if the default is set to 2, you'll have new users asking why the IK constraint "unexpectedly" stops influencing after just a couple bones.
Because of this, I wonder if this proposal isn't addressing a symptom, rather than the actual problem of poor documentation and visual feedback when applying the constraint.
Setting it to 1 might be the worse of both worlds. :)
Part of this might have to do with rigging style. It's not uncommon for rigs in Blender to consist of discontinuous bone chains (that is, there's a parent relationship between the arm chain and the spine chain, but no explicit bone connecting the two; just the parent relationship). This is particularly true in the case of first-time riggers. In that case, if you apply an IK constraint to the arm, the default chain length of 0 gives exactly what's expected (the IK constraint only affects continuous bone chains, so it stops at the shoulder).
For experienced riggers, there's typically more advantages to keeping the bone chain continuous... but for those riggers, they're more likely to go in and fiddle with chain length values... so the default length of 0 is less likely to throw them off. That said, it could get to be pretty annoying if you have to go in and adjust chain lengths every single time.
I wonder if there's a pleasant middle ground. When you create an IK constraint, there is a dashed line drawn from the tip of the constrained bone to the head of the bone at the end of chain. Perhaps that line should also be there when you select the constrained bone, too.
We might also pull in a behavior from the Auto IK feature. When Auto IK is enabled (but no IK constraint exists), you can interactively change the chain length value by using <kbd>Ctrl</kbd>+MouseScroll. If that feature existed for the regular IK constraint, it might help make changing the chain length value less tedious.
Yeah, the default of 1 was a suggestion to at least be consistent.. no matter what, you apply the constraint to the bone, and that's the bone that's affected.
the question I have though is how often do people actually use ik constraints that go more than 2 bones?