Rigging

Source: src/mpfb/ui/rigging/standardrig/

Parent panel: MPFB_PT_Rig_Panel ("Rigging")

Overview

The "Standard rig" panel covers the non-rigify rigging workflow. It is the recommended path for characters that do not need a rigify rig — game-engine exports, the MakeHuman default rig, the Mixamo skeleton, OpenPose, and so on.

The panel is always visible whenever the parent Rigging panel is visible, and is expanded by default. Its draw content depends on the state of the active object:

• No armature associated with the active object — draws the "Add standard rig" controls (rig type, import weights, Add standard rig).
• Active object is a default rig (RigService.identify_rig() returns "default" or "default_no_toes") — draws the absorbed "Rig helpers" controls; when no helpers are active, it shows configuration boxes and an Add helpers button; when at least one helper mode is set, it shows only a Remove helpers button.
• Otherwise (rigify meta rig, generated rigify rig, game engine, mixamo, CMU MB, OpenPose, a custom rig, or any other non-default rig) — a single label explaining the panel is not applicable. Adding helpers is only supported on the default rig variants.

Panel

MPFB_PT_Standard_Rig_Panel ("Standard rig")

Attribute	Value
bl_label	"Standard rig"
bl_category	MODELCATEGORY
bl_parent_id	MPFB_PT_Rig_Panel
bl_options	set() (expanded by default)
Base class	Abstract_Panel
Scene properties prefixes	"ADR_" (from properties/), "SIK_" (from helperproperties/)
Object properties prefix	"rh_" (from rigproperties/, stored on the armature object)

Operators

MPFB_OT_AddStandardRigOperator

Attribute	Value
bl_idname	mpfb.add_standard_rig
bl_label	"Add standard rig"
bl_options	{'REGISTER', 'UNDO'}
Poll	BASEMESH_ACTIVE

Adds the rig selected in standard_rig to the active basemesh using HumanService.add_builtin_rig(). If import_weights is enabled and a weights file exists for the chosen rig, the vertex group weights are set up at the same time.

Rig helpers

The "Rig helpers" UI is part of the Standard rig panel. It adds IK (Inverse Kinematics) helper bones to a character's standard rig. Without helpers, animating a character requires rotating every bone in a chain manually (FK — Forward Kinematics). With IK helpers, you instead move a single target bone (for example, the hand or foot) and Blender automatically calculates the positions of all the bones in the chain leading up to it.

Separate helpers can be added for arms, legs, fingers, and eyes. Each limb type has multiple configuration options controlling the exact helper structure and how the IK targets relate to each other.

Important limitation: Rig helpers are only supported on the Default and Default (no toes) rigs. The add operator validates this by checking for the levator03.L bone, which only exists in those rigs.

MPFB_OT_AddHelpersOperator

Attribute	Value
bl_idname	mpfb.add_helpers
bl_label	"Add helpers"
bl_options	{'REGISTER', 'UNDO'}
Poll	ANY_ARMATURE_OBJECT_ACTIVE

Adds the configured IK helper bones to the active armature. Steps:

1. Validates that the rig is a supported type (checks for levator03.L).
2. For each enabled limb type, creates the appropriate helper entity class (ArmHelpers, LegHelpers, FingerHelpers, EyeHelpers from src/mpfb/entities/rigging/) and calls the IK setup method.
3. After adding, stores the resulting mode string (e.g. "IK") in the rig's object properties (arm_mode, leg_mode, finger_mode, eye_mode).
4. If preserve_fk is disabled, resets all bones to rest pose before adding helpers.
5. Normalises rotation modes on all bones after setup.
6. If hide_fk is enabled, hides the FK bones that are now driven by the IK helpers.

MPFB_OT_RemoveHelpersOperator

Attribute	Value
bl_idname	mpfb.remove_helpers
bl_label	"Remove helpers"
bl_options	{'REGISTER', 'UNDO'}
Poll	Custom: at least one limb mode must be active (arm/leg/finger/eye mode non-empty)

Removes all active IK helper bones from the armature. For each limb type that has a non-empty mode, it calls the corresponding remove_ik() method on the helper entity class. After removal, clears all four mode object properties (arm_mode, leg_mode, finger_mode, eye_mode) back to empty strings.

Properties

Add standard rig scene properties (from JSON, prefix "ADR_")

Property	Type	Default	Description
standard_rig	enum	"default_no_toes"	Which built-in standard rig to add. Options: default (Default), default_no_toes (Default without toe bones), game_engine (Game Engine), game_engine_with_breast (Game Engine with breast bones), cmu_mb (CMU MB), mixamo (Mixamo), mixamo_unity (Mixamo with Unity extensions), openpose (OpenPose BODY_25, no hands).
import_weights	boolean	true	When adding a standard rig, also import the corresponding vertex weight file if one is available.

Rig helpers scene properties (from JSON, prefix "SIK_")

These are stored in the Blender scene and apply to the next Add helpers operation.

Arm settings

Property	Type	Default	Description
arm_helpers_type	enum	"LOWERUPPER"	IK structure for the arms. NONE — no arm helpers; LOWERUPPER — two separate IK targets, one for the lower arm (wrist/hand) and one for the upper arm (elbow); LOWERUPPERSHOULDER — three targets, adding a shoulder target; ARMCHAIN — a single IK chain covering lower and upper arm; SHOULDERCHAIN — a single IK chain including the shoulder.
arm_parenting_strategy	enum	"SPINE"	Which bone to use as the parent for the arm IK target bones. NONE — no parent (world space); ROOT — root bone; SPINE — the last bone in the spine chain; OUTER — the hand target is the parent of the elbow target; INNER — the elbow target is the parent of the hand target.
arm_target_rotates_hand	boolean	true	When the IK target bone is rotated, also apply that rotation to the hand bone. Useful for posing the wrist.
arm_target_rotates_lower_arm	boolean	true	When the IK target bone is rotated, partially rotate the lower arm around its Y axis (forearm twist).

Leg settings

Property	Type	Default	Description
leg_helpers_type	enum	"LOWERUPPER"	IK structure for the legs. NONE — no leg helpers; LOWERUPPER — two separate IK targets, one for the lower leg (foot) and one for the upper leg (knee); LOWERUPPERHIP — three targets, adding a hip target.
leg_parenting_strategy	enum	"NONE"	Which bone to use as the parent for the leg IK target bones. NONE — no parent; ROOT — root bone; OUTER — foot target is the parent of the knee target; INNER — knee target is the parent of the foot target.
leg_target_rotates_foot	boolean	true	When the IK target bone is rotated, also rotate the foot bone.
leg_target_rotates_lower_leg	boolean	true	When the IK target bone is rotated, partially rotate the lower leg around its Y axis (shin twist).

Finger settings

Property	Type	Default	Description
finger_helpers_type	enum	"GRIP_AND_MASTER"	IK structure for the fingers. NONE — no finger helpers; POINT — one IK point target per finger, used to direct each fingertip; GRIP — one helper bone per finger that curls it when rotated; MASTER — one combined helper that curls all fingers simultaneously; GRIP_AND_MASTER — both individual grip helpers and a master grip helper.

Eye settings

Property	Type	Default	Description
eye_ik	boolean	true	Add a central IK target bone in front of the face that both eyes track toward. Useful for making a character look at a specific point.
eye_parenting_strategy	enum	"HEAD"	Which bone to use as the parent for the central eye IK target. NONE — no parent; ROOT — root bone; HEAD — head bone (the target moves with the head as the character moves).

General settings

Property	Type	Default	Description
hide_fk	boolean	true	Hide the original FK bones that are now being driven by the IK helpers. Reduces viewport clutter while posing.
preserve_fk	boolean	true	Try to maintain the current pose when adding helpers. If disabled, all bones are reset to rest pose before helpers are added, which can produce more predictable IK results but loses any existing pose.

Object properties (stored on the armature object, prefix "rh_")

These properties are stored directly on the armature object rather than in the scene. This means each rig in the file can have different helper states, and the state persists when you save and reopen the file. They are managed automatically by the Add/Remove operators — you do not normally set them manually.

Property	Type	Default	Description
arm_mode	string	""	Records whether arm helpers are currently active and in what mode (e.g. "IK"). Empty means no arm helpers have been added.
leg_mode	string	""	Records whether leg helpers are currently active. Empty means no leg helpers have been added.
finger_mode	string	""	Records whether finger helpers are currently active. Empty means no finger helpers have been added.
eye_mode	string	""	Records whether eye helpers are currently active. Empty means no eye helpers have been added.

Related

• rigifyrig.md — the rigify workflow (add metarig + generate)
• customrig.md — adding a user-supplied custom rig
• rigops.md — legacy "convert to rigify" workflow
• ArmHelpers / DefaultArmHelpers — entity class that implements arm IK helper creation
• LegHelpers / DefaultLegHelpers — entity class that implements leg IK helper creation
• FingerHelpers / DefaultFingerHelpers — entity class that implements finger IK helper creation
• EyeHelpers / DefaultEyeHelpers — entity class that implements eye IK helper creation
• RigService — the service that handles rig creation and management