limit distance of ik constraint to another bone

pete

Is there a way to limit the distance an IK constraint can move from another bone, while still allowing the IK constraint to move before hitting that limit? I made a character with limbs that stretch but only to a certain length, and I don't want the IK constraint handle to move past the end of the limb when it hits max length.

Misaki

pete Spinebot's answer is correct assuming functionality up to version 4.2, but please note that the situation has changed significantly with the major enhancements to transform constraints and the addition of the new Slider feature in 4.3-beta!
For an overview of the improvements to transform constraints functionality, please refer to our blog post:
https://esotericsoftware.com/blog/The-4.3-beta-is-now-available

One option I'd especially like you to pay attention to is Clamp, which allows you to restrict constrained bone values so they don't exceed a specific range. By applying this to the IK target bone, you can limit the range within which the IK target bone can move.

Sliders offer a different approach, but they can also be used when you want to limit the range of a bone's transformation. While detailed documentation is not yet available, you can try 4.3-beta yourself anytime, so we'd be delighted if you could give it a try.

Spinebot

To limit the distance an IK constraint can move from another bone, you can use the "Stretch" property of IK constraints. This property allows the constrained bones to scale larger when the distance to the target bone exceeds the constrained bones' lengths. However, it does not inherently prevent the IK target from moving beyond the maximum stretch length. You can manually position the IK target near the maximum range to visually limit its movement. Alternatively, you can use path constraints to achieve a similar effect by constraining bones to a path and controlling the path's length.