Adding IK to the legs without affecting underlying animation.

Hi there,

I'm stuck with this, basically, I'd like to be able to move the hips of my character a little and preserve the underlying walk animation. So the legs would squash a little but the feet would keep contacting the same position and rotation, is that possible I can't figure it out



Thanks,
Pete

 

Okay I managed to get the position to work, but it feels a bit hacky and doesn't work with rotation at all.

Here's my code, I don't now how I can just alter the hip pos directly so I'm offsetting the foot pos based on it's movement. Does anyone have any experience with this stuff?

Code (CSharp):

1.     void OnAnimatorIK(int layerIndex)
2.     {
3.         //Left
4.         //Get pos and rotation of feet
5.         lTarget.position = anim.GetIKPosition(AvatarIKGoal.LeftFoot);
6.         lTarget.rotation = anim.GetIKRotation(AvatarIKGoal.LeftFoot);
7.         //Set IK weights
8.         anim.SetIKPositionWeight(AvatarIKGoal.LeftFoot, 1);
9.         anim.SetIKRotationWeight(AvatarIKGoal.LeftFoot, 1);
10.         //Add the current offset of the character base
11.         lTarget.position += (hipTarget.position - hipCharacterBase.position);
12.         //Set the new IK target pos and rotation
13.         anim.SetIKPosition(AvatarIKGoal.LeftFoot, lTarget.position);
14.         anim.SetIKRotation(AvatarIKGoal.LeftFoot, lTarget.rotation);

I want to be able to do this and keep the feet stuck down.

 

One way to accomplish this is to create an additive layer excluding all bones except the hip/root bone. Create 1-3 simple root bone animations and put them into a blend tree. The blend tree allows you to control the rotation angle based on a blend parameter. The additive layer would allow for the existing animation to perform as it does while adding rotation/transformation to the hips/root.

 

Awesome thanks @theANMATOR2b! I’ll check it out

 

Hey @theANMATOR2b, I tried that and it seems to work but this is already 5 extra animation clips and it doesn't include vertical movement.
@Mecanim-Dev, is there a way to directly transform the hips while keeping the foot animation intact?

 

Hi @petey

have you try to simply lower animator.bodyPosition ?
https://docs.unity3d.com/ScriptReference/Animator-bodyPosition.html

Code (CSharp):

1.  
2. public class OffsetHips : MonoBehaviour
3. {
4.     public Vector3 hipsOffset;
5.  
6.  
7.     Animator m_Animator;
8.     void Start()
9.     {
10.         m_Animator = GetComponent<Animator>();
11.     }
12.     private void OnAnimatorIK(int layerIndex)
13.     {
14.         if (layerIndex == 0)
15.         {
16.             m_Animator.bodyPosition += hipsOffset;
17.  
18.             //Set IK weights
19.             m_Animator.SetIKPositionWeight(AvatarIKGoal.LeftFoot, 1);
20.             m_Animator.SetIKRotationWeight(AvatarIKGoal.LeftFoot, 1);
21.             m_Animator.SetIKPositionWeight(AvatarIKGoal.RightFoot, 1);
22.             m_Animator.SetIKRotationWeight(AvatarIKGoal.RightFoot, 1);
23.  
24.         }
25.     }
26. }

 

Awesome, @Mecanim-Dev! I thought there might have been a way. Thanks for posting the code snippet

 

Hey @Mecanim-Dev, sorry to drag this up but I was wondering if you might have a good suggestion for this.
I'm just running in to a bit of trouble because if you apply transforms to the .bodyPosition they run local to the mecanim character root, but bodyRotation is local to the hip bone. Is there a way to apply rotations in the root space as well?
I feel there is probably a good quaternion way to do this but I'm struggling at the moment...

Thanks!
Pete

 

Hey I think I got it!

Code (CSharp):

1. Quaternion originalrotation = m_Animator.bodyRotation;
2. Quaternion offset = originalrotation *Quaternion.Inverse(referenceRotation.rotation);
3. m_Animator.bodyRotation = targetTransform.rotation * offset;

Does that seem okay? Looks like it's doing the trick