(As of version 1.05.00)
The ‘HumanIK’ attachment help you define the joints and ctrls of the node into Maya’s HumanIK system (HIK)..
Rigs setup correctly for HIK offer a variety of functionalities, including motion capture within and outside Maya, full-body IK, animating the rig in Autodesk MotionBuilder, character retargeting, integration with certain features in game engines, and more.
For more detailed information about ‘Autodesk HIK‘.
How to use the ‘HumanIK’ attachment:
It’s recommended to use the ‘CA_Biped_Game’ preset for rigging your character, as Maya’s HIK system behaves best on rigs with a single joint chain hierarchy.
To apply the ‘HumanIK’ attachment:
- Select the following 6 nodes on your character: left leg, right leg, left arm, right arm, spine, and head.
- Go to the ‘Batch‘ menu and choose ‘Add Attachment To Selected Nodes‘ -> ‘HumanIK‘. This action attaches a ‘HumanIK’ attachment to each selected node.
If you are using the ‘CA_Biped_Game’ preset or using the appropriate nodes for each body part (e.g., ‘CA_Leg‘ for legs, ‘CA_Spine‘ for the spine), Arise will automatically define the correct joints and ctrls for you. Otherwise, you can define them manually using the attributes explained in the following section.
Now, whenever you rebuild your nodes, Arise will define your rig into the HIK system.
Attributes:
- ‘Define Joints’ – Checkbox to enable joint definition on the selected node as HIK joints.
- ‘Only Skinning Joints’ – Filter to display only skinning joints of the node.
- ‘HumanIK Joints’ – A table attribute listing the joints eligible for HIK definition.
- ‘define_HIK_joint’ – Checkbox to allow defining the specified joint for HIK.
- ‘HIK_definition’ – Dropdown menu to select how the joint should be defined in the HIK system.
- ‘Reset Changes’ – Button to revert any modifications made in the ‘HumanIK Joints’ table.
- ‘Define Ctrls’ – Checkbox to enable ctrls definition on the selected node as HIK ctrls.
- ‘HumanIK Ctrls’ – A table attribute listing all the ctrls that can be defined for HIK.
- ‘define_HIK_ctrl‘ – Checkbox to allow the definition of specified ctrls for HIK.
- ‘HIK_definition’ – Dropdown menu to select how the ctrl should be defined in the HIK system.
- ‘Reset Changes’ – Button to revert any modifications made in the ‘HumanIK Ctrls’ table.
Requirements for Autodesk HIK system:
To ensure proper functionality, HIK requires certain conditions to be met:
- A minimum of 6 nodes need to be defined with ‘HumanIK’ attachments: spine, head, left leg, right leg, left arm, and right arm (optional: left fingers and right fingers).
- Each body part has limitations on the number of joints it can accommodate:
- The spine node can only take up to 9 joints, meaning the node should not have more than 9 ‘Ribbon Joints‘.
- The arm node can only take up to 5 roll joints, meaning the node should not have more than 6 ‘Ribbon Joints‘.
- The leg node can only take up to 5 roll joints, meaning the node should not have more than 6 ‘Ribbon Joints‘.
- The head node can have up to 9 neck joints, meaning the node should not have more than 9 ‘Ribbon Joints‘.
Limitations:
- Maya’s HIK system is designed for humanoid rigs (2 legs, 2 arms, 1 spine, 1 head).
- HIK performs better with IK ctrls defined rather than FK ctrls.
- HIK will error if a body part has more ctrls defined than joints defined. This is currently only relevant for the ‘CA_Spine‘ node, where you can control separately how many ctrls and joints the node has.
- If for example, you define a shoulder ctrl without defining a shoulder joint, HumanIK will encounter an error.
- HIK can function without a single joint chain hierarchy but will have limited functionality and might not behave as expected. Use ‘FollowSkeleton‘ attachments to establish a single joint chain hierarchy before adding ‘HumanIK’ attachments. If you are using the ‘CA_Biped_Game’ preset, you will only need to add the ‘HumanIK’ attachments to the 6 nodes explained in the sections above.
- If using ‘FollowSkeleton‘ with ‘Support Scale’ enabled, untick the attribute ‘Only Skinning Joints’ in the ‘HumanIK’ attributes section, then untick all the ‘SCALE_FS’ joints and instead tick all the ‘_FS’ joints inside the ‘HumanIK Joints’ table attribute.
- Maya’s HumanIK system, on which the Arise HumanIK attachment is built, expects the character to meet several strict conditions at the time of definition: a clean T-pose, arms extended straight out at 90° from the torso, straight legs, no bend in the elbows, knees, or spine, and no joint twisting.
Arise automatically satisfies these requirements when the arms, legs, torso, and head nodes have ‘Clean Transformations’ disabled, allowing the ‘World Orientations’ attributes to be used (Default). These conditions are also met when the character is modeled in a perfect T-pose.
It should be noted that ‘World Orientations’ currently do not behave reliably when Maya’s world up axis is set to Z. Therefore, unless the character is modeled in a clean T-pose, mocap retargeting may not behave as expected.
