How would I weld a part to a torso without breaking the inverse kinematics joint?

Hello Devs,
I am trying to recreate Unity procedural animation tutorial (10 steps) - YouTube this spider ik animation. The steps where you rotate the torso to the orientation of the raycasted part, raycasting the attachment to the height of the ground is no problem, but I am getting stuck on this part:

I am using the IK Controls are now out of beta! Ik controls in order to connect my leg to the part. the leg is rigged with a motor6d to the torso of the spider. The End part of the spider moves to the attchment on the ground. Everything works fine (f.e. moving the leg towards the attachment when distance between these two gets two big, only that the upper leg doesnt stay on the spiders torso. I tried adding a Hinge Constraints but this destroys the whole ik movement…

above is a really bad example of the spider leg( i made a better one). The last leg moves to an invisible attachment. Now if I move the Torso of the spider by adding a tween, the leg doesn’t stays on the torso. In the video I linked above you can clearly see on step 0:33 that the whole leg moves with the torso while the last leg stays on position with the attachment. How would I be able to do this?
Any help is highly appreciated, I tried to fix this for hours…

As you can see here that if the torso moves, the end part stays with the (invisible) attachment while the other parts stay with it, but the first part does not stick with the torso.

Have you tried using another Motor6D attachment? You probably don’t need one for the lower leg, just link/attach them like a chain.

Yeah I am using a plugin which creates a joint (motor6d attachment) to every part. I already attached them like a chain, the lower part with the torso, but still when the torso moves it doesnt stick to the torso sadly :frowning:

Nono, what I meant was something like this:

Torso to Upper Leg, Upper Leg to Lower Leg, and then Torso to Lower Leg for your IK. Try using other constraints, like ball constraints, instead of the Motor6Ds.

1 Like

Sorry for the late reply, I will def try this tomorrow. This could be a great way to so,ve this

1 Like

(Btw where should I place the position of the joint between the torso and the lower leg?)

I’m not sure, I haven’t messed with IK yet, so I’m just going off common sense.

Hey there,
I just tried out your ideas but sadly none of them worked. my studio always instantly crashed when i tried to play the game when adding a third motor6d between the lower leg and the torso, dont ask me why lol. Adding a ball constraint did nothing too sadly…

maybe I did not implement the things you suggested as right as the intention of them…


I just removed the motor 6d of the nearest part of the torso and it now works. The only thingy is that the nearest part to the torso wont move :frowning: maybe ill get this working too!!!

This is the problem:
this is what it looks like, when i have a ball constraint attached to the upper part and the torso (only 2 parts move):

and this is how it looks llike when there is only the motor 6d (every part moves, only the upper part doesnt stick to torso):

(Sorry for the many updates)
i think i fixed it:

I dont know if there are any more elegant ways to solve this but im quite happy with this :smiley:

Finished result:

works perfectly :smiley:


This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.