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quad.legacy

Full IK/FK quadruped leg rig template module

Overview​

quad.legacy provides a complete IK/FK rig for a quadruped leg. It shares a common module base with arm.legacy and leg.legacy, meaning their construction and logic are largely identical.

The module combines:

  • A 2-joint IK chain plus an aim constraint on the 3rd joint for quadruped-style legs
  • Optional clavicle support for front legs
  • Reverse foot setup for stable contact and foot rolls
  • Stretch, soft IK, and squash-volume compensation
  • Twist and roll joints for smooth deformation

Template Structure​

  • The root of the template marks the hip position.

  • The rest of the chain defines, in order:

    • knee
    • ankle
    • tarsus (heel/mid-foot)
    • toe tip

  • You do not need to orient the joints manually. Orientation is handled automatically during rig build.

  • The heel joint is placed separately and defines the pivot of the reverse foot system.

For forelegs, an optional clavicle joint can be added and parented backwards to the hip. This joint defines the pivot for the clavicle rig, to which the leg will be parented.

The template hierarchy is strict and must not be modified, otherwise the build may fail or produce unexpected results.

Options​

Quadruped Type

  • quad_type (enum, default: down) Defines how the quadruped leg IK is oriented. The quad leg uses a 2-joint IK chain with the third joint driven by an aim constraint pointing to the opposite end of the chain.
    • down : The 3rd joint (ankle_quad) aims toward the hip.
    • up : The 1st joint (hip) aims toward the foot.

Clavicle and Reverse Foot

  • clavicle (bool, default: on) Enables the clavicle rig, using the optional clavicle template joint as the pivot for the front leg.
  • reverse_lock (bool, default: off) Enables the reverse foot locking system (heel / ball / toe pivots).
  • bank (bool, default: off) Enables lateral foot banking controls within the reverse foot system, allowing the animator to tilt the foot inward or outward.

Effector Plane & Pole Vector

  • effector_plane (enum, default: ground) Up-vector mode for auto-orienting the 3 main “foot” joints.
    • x, y, z : World up vectors
    • auto : Auto up vector based on joint geometry (good for wings)
    • ground : Forces perpendicular-to-ground orientation (useful for feet)
  • pv_space (id, default: space.cog) Global parent space for the pole vector.
  • pv_space_default (float, min: 0, max: 1, default: 1) Default weight for pole-vector space switching.

IK Stretching

  • default_stretch (bool, default: on) Enables IK stretching at build time.
  • soft_distance (float, min: 0, max: 1, default: 0.05) Threshold (percentage of stretch distance) where soft IK starts to blend in.
  • stomp_power (float, min: -1, max: 0, default: -0.5) Power falloff used for squash/volume compensation. -0.5 corresponds to inverse square-root falloff.

Interpolation & Roll Joints

  • blend_joints (bool, default: on) Enables roll joints at key articulations for deformation smoothing.

Twist System

  • splits_up (int, min: 2, default: 3)
  • splits_mid (int, min: 2, default: 3)
  • splits_dn (int, min: 2, default: 3) Number of twist joints for upper, mid, and rear sections of the leg.

Space Switching

  • space_switch (bool, default: on) Adds default space-switch modes to important controllers.

Not Yet Implemented​

  • aim_axis (enum, default: -y): Not yet supported.
  • up_axis (enum, default: -x): Not yet supported.
  • up_axis2 (enum, default: z): Not yet supported.