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Request function for IK

ryancbaker

For one bone suits me like it is done now, but with a small correction. This is the ability to scale the bone when the target is closer than the length of the bone.

Hi, Belpetr. To fix the above issue (the one shown in your video of the spider), select the bone you are stretching (in this case, the spider web strand), and set its X scale to something very small - like 0.001. It will still stretch to match the spider's location, but now it can also shrink down to the scale you set (0.001). With this setting, it should both stretch and compress to match the spider's location.

Nate

In 3.7.25-beta:
Loading Image
2 bone IK only has Stretch, not Compress or Uniform. Only Stretch and Compress are keyable, Uniform is not.

belpetr

Thanks for your work. This will really make it easier for me to work on many animations.

I wanted to ask for a little more functionality for animations with IK.

Now when using IK with two bones, we can animate two objects. This is the parent bone and the target. It would be great to be able to shift the child's bone, as it would be the target for the parent and be able to stretch and compress between the parent bone and the target. So we could create the illusion of the rotation of the leg in 3d.

Crocodilum

So promising, can't wait to test the stretch one!

Nate

3.7.25-beta is up, so you can try it now!

belpetr wrote
It would be great to be able to shift the child's bone

You've always been able to translate the child bone. The problem with scaling the parent bone is that it almost always causes the child bone to need to rotate to continue pointing at the target, especially with non-uniform scaling. Also, scaling the parent bone will shear the child bone, which is unlikely to be what you want. Maybe you'd be better off using two 1-bone IKs?

belpetr

Nate wrote
3.7.25-beta is up, so you can try it now!

belpetr wrote
It would be great to be able to shift the child's bone

You've always been able to translate the child bone. The problem with scaling the parent bone is that it almost always causes the child bone to need to rotate to continue pointing at the target, especially with non-uniform scaling. Also, scaling the parent bone will shear the child bone, which is unlikely to be what you want. Maybe you'd be better off using two 1-bone IKs?

This is a good solution for one animation. But if the character's leg should move in different ways then this is not a very good decision. For example, in the idle, it is slightly rocked. Another animation twists slightly. In the third it runs. In the fourth, it jumps.

I tried to solve the knee turns problem with scaling IK bones. There I found a bug. If the child is not exactly look at the tip of the parent, then the parent bone abruptly unfolds on the child when it scaling.

Nate

This is not a bug, it is an IK limitation.

If the IK mix is greater than zero and the parent IK bone has nonuniform local scale (meaning the X and Y scale have different values), then the child IK bone's local Y will snap to 0. Inheriting nonuniform scale does not trigger this snapping.

Spine's IK is the only I've ever seen that allows nonuniform scale at all. It was a very complex problem to solve and requires the child bone Y to be zero.

Your knee turning problem is not very clear to me. I saw your video above, but I'm not sure what you wanted by translating the child bone. Form your image it looks like you want the bones to bend the other way? Maybe you can animate the IK mix to zero, placing the FK bones so the leg is straight when the mix is zero, then flip the IK bend direction and animate the IK mix back to 100%.

belpetr

Here is an example implemented in another program. It illustrates well what I am talking about.
Cartoon Animator 4 - Smart IK Motion Editing - Works with All Kinds of Animal Characters - YouTube
and
Cartoon Animator 4 (CrazyTalk Animator) - Smart IK Motion Editing - Stretch Animation - YouTube

Here is another program implementation of the feature I asked to add before.

https://docs.2dimensions.com/support/nima/the-interface/selection-panel

Erika

Hello Belpetr, if you set two IK constraints with one bone that have the stretch and compressed options turned on, you can achieve the same effect of "Freeze "Joints On" while the first one just requires one IK with said options.

Nate

That's true Erika, though when you move the target of the lower 1-bone IK, it won't do IK for both bones.

There may be something we can do to improve translation of the second IK bone, like in the videos above. What happens now is the translation is applied to the FK pose, which tends to make the IK pose surprising.

papamadoo

I stumble in this threat looking through bug, And since the now stretch compress option is release, I try to experiment on building leg, arm without using the conventional way.

to make some blend between functionality and possibility.

Its a work around I think, but look close to what is the need

belpetr

papamadoo, this solves the problem with the knee or elbow, but makes it impossible to use inverse kinematics. That is why there is a need to expand the functionality, especially for the 2D program.