IK Controls

IK Controls

The IK Controls panel (Inverse Kinematics) can be found in the Properties Sidebar of the 3D Viewport (if the sidebar is hidden: ensure the mouse is in the 3D Viewport, then hit the N key to toggle the sidebar visibility). The panel displays different sets of properties depending on what bones are currently selected and visible.
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The IK Bones for the arm are visible and enabled.

However, you can force the Panel to always show all controls regardless which bones are selected by checking the tick box at the top of the panel (see image).

You can unhide (display) the yellow IK Control bones by clicking on the Buttons IK Arms and IK Legs. And you can activate the IK Control Bones by ticking on the empty square right to the Buttons (See image)

Note: When you see a green tick right to a button (see image above), then the corresponding IK bones are enabled. However Avastar displays the corresponding bone properties only when you have also selected the IK Bones in the Viewport.

Chain Controls (Targetless IK)

The Chain controls are only available for the (green) control bones except: the EyeTarget, The COG Bone and the Origin.

The Avastar bones are organized in parent/child chains. These chains are used for targetless IK. That is when you grab one bone along a chain, all bones of the chain follow along the movement of the active bone. For example when you move a wrist or an ankle, the entire arm/leg will be repositioned in a meaningful way.

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The Chain Control is only shown when the active and selected bone is a green control Bone.

Once you understand how these controls work you will find that positioning a character becomes very fast and easy.

The Chain ends

In the top row of the Chain controls subpanel you see the Chain end points for the active (selected)bone. The left entry is the chain start bone, which is always the active Bone. The right entry is the end of the kinematic chain.

Below the Chain display you find 5 control Buttons which allow you to quickly modify the end of the Chain:

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Parent

The chain begins at the current bone and ends at the Bone’s parent. This is the smallest possible IK Chain (contains only one bone).

COG (Center Of Gravity)

All kinematic chains end at the COG Bone, So the COG Bone will always be the most distant bone that you can choose.

Limb

The chain start at the current bone and ends at the last limb bone. These are:

  • The Hips (for the leg chains)
  • The Collars (for the arm chains)

Less & More

With these Buttons you can elongate the Bone chain until the chain end reaches the COG Bone, or you can shrink it until the chain end is the parent of the active and selected bone.

Note: Each bone has its own targetless IK Chain. So it is possible for example to configure the Wrist bone’s chain to reach up to the COG Bone, while the Collar Bone’s chain already ends at the Torso.

The Chain Tip Movement:

The second set of buttons affects how the selected bone behaves when it is moved in Pose mode. In the example below i have moved the Avastar’s mNeck Bone along the X-Axis to demonstrate the difference between Clamped and Free Bone Tip Movement:

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Clamped: Bone orientation does not change while bone is moved

Clamped: the chain tip can be moved but won’t be rotated. It will keep its orientation in space as it’s dragged around.

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Free: Bone Orientation is controlled by the IK Resolver

Free: the chain tip moves/(rotated) freely with the movement of the bones

Influence

The Influence value specifies how much the bone actually modifies its IK chain when moved around. So a value of 0 effectively disables all influences of the bone movement to its IK chain, while a value of one give maximum influence. Normally you want to keep the influence at 1.0
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IK Targets

Avastar provides 4 IK Target bones, 2 for the Arms and 2 for the legs. These bones are displayed in yellow. besides the target bones we also provide 4 Pole targets which can be used to adjust the knees and the elbows.

The pole targets are connected to the skeleton via helper bones to visualize where they influence the Skeleton.

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IK bone Controls

The 4 IK Control bones (yellow, see in the section about “Avatar bones”) can be used to clamp the limbs at fixed positions. We have 3 sliders for each limb plus 2 additional sliders for the Foot Pivot. I have enabled Show all controls so we can see the control parameters without actually selecting the bones.

IK/FK influence:

The 4 top most sliders (Left Arm, Right Arm, Left Leg and Right Leg) define the amount of influence that is applied from the IK Control bones to the corresponding limbs.

By default the IK influence is set to 0, that is: the bones are completely decoupled from the IK control bones and thus they behave solely as FK bones (FK==forward kinematics).

If you move the sliders towards 1, then the current location of the IK bone controller gets more influence on where the tip of the corresponding bone chain is located. When set to 1, then the tip of the limb chain is fully clamped to the IK Control bone.

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Note: You will use the IK Bones when you want the feet or arms to rest fixed at a location, while the rest of the body moves.

Foot Pivot

When rotating a foot, you can define the pivot point around which the foot is rotated. Normally this is located at the heel, so that the foot itself goes up and down. The foot pivot sliders allow to adjust the point anywhere between the Heel and the Toe.
IK_controls_09Note: Blender allows key-framing of sliders as well as of bones.

Target Align

When you have selected one or more bones which belong to a bone chain, then an additional subpanel opens. The Target Align panel allows to set the IK Properties of the rig. By default the properties area is collapsed as shown in he image. We will describe the content of this area below in more detail.
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The Target Align Panel.

Note: Click on the Button Align to Pose to set all affected parameters at once (see next chapter for details)

Wrist & Ankle Rotation

The targetless IK is a great way of posing a character. However, when you want to switch to targeted IK in the middle of your animation, then you will see a mismatch of the IK Control Bones to their corresponding Wrist or Ankle Bone.

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IK Control Bones mismatch

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IK Control Bones match after apply the Match Operators.

You can fix the IK Bone location easily in the IK system using the Target Align subpanel:

In the Target Align Panel you find up to 4 Match Buttons (depending on which of the IK Control Bones you have selected):

  • Match Left Wrist.
  • Match Right Wrist.
  • Match Left Ankle.
  • Match Right Ankle.

These Operators copy the current rotation and location of the corresponding wrist bone or ankle bone to its IK Controller.

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The Target Align Buttons only appear when you have selected an IK Control Bone (yellow)

Set Target

While you work with the IK Bones the target poles often get into weird positions. You may then want to reposition the poles to a more convenient place without destroying the current pose:

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Before Set Target is called the connection line can be at an arbitrary orientation.

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After Set Target is called the connection line is oriented perpendicular to the shoulder bone.

 

In the Target Align Panel you find up to 4 Set Target Buttons (depending on which of the IK Control Bones you have selected) similar to the Match Buttons (see image).
These Operators orient the connection line between the pole target and its corresponding bone perpendicular to each other.
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Set Hinge

The hinge sliders define how much the wrist rotation is influenced by the IK bone controllers.

  • Slide it to the left (0.0): The IK Control bone has no influence on the wrist rotation.
  • Slide it to the right (1.0): The rotation of the IK control bone is fully applied to the wrist.