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I'm trying to copy the rotation of the target bone of a leg chain to the foot, like in this tutorial.

enter image description here

Thing is, Blender has changed and the constraint has not the same options than before. I don't understand which settings I should use to have my feet following the IK target rotation correctly.

ouch it hurts!

I managed to have a rotation constraint, but the rotations go in the wrong directions. Also, the offset mode (as used in the tutorial) is labeled "legacy" in Blender 3.3.0, so maybe I should use different settings.

I'm quite new to armatures. Maybe I'm doing something wrong. Guess this is related to the bones orientations.

I also did a Recalculate Roll Global +Y axis, I don't know if I needed to.

Could someone explain what's going wrong and how I could fix it ? I don't just want to fix it, I want to understand it.

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The video's "offset" is, yes, the same as setting the Mix mode to "Offset (Legacy)".

This wasn't ever a good way to do it, even when the video was made. Offset world space rotation isn't what you want; it wasn't a well-considered way to mix rotations in the first place, which is why it's now considered legacy. It exists only to support older files. The video, in my opinion, offers poor advice.

However, the modes that have been made to replace Offset are, still, not necessarily well-considered. There is no simple, single mode change that will make the Copy Rotation work as you want.

Instead, to make it work properly, we can add mechanism bones, that exist only to make our constraints work properly, not intended to deform the mesh or to be manipulated as controls.

Start by duplicating your feet bone, then parent these bones to your IK targets. Parent these duplicates to the appropriate IK target. Disable "deform" property on these new bones, in properties/bone/deform. It's not necessary, but I'm going to also name and scale these duplicates down, so that we can easily see which is the deforming foot bone and which is the duplicate:

enter image description here

Now we'll enter pose mode. Delete the constraints from these duplicates. Change the copy rotation constraint on your foot bones to target these duplicates, on world->world, with "replace" mode:

enter image description here

Because the new bones are duplicates of the constrained bones, their axes point in the exact same directions as the constrained bones at rest; as we rotate their parent, the foot bone follows that rotation perfectly, regardless of the parent's axes.

Note that Moonboot's suggestion to parent the foot to the IK is a valid alternative (if you then follow it with a copy location constraint targeting the tail of calf), it does the exact same thing barring bone scaling, but I didn't demonstrate that because you specifically asked about copy rotation.

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Choose Target and Owner > Local Space, or maybe simply parent the foot to the controller?

enter image description here

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