Constraint System Manual

Auto Biped Constraint Setup Utility

In v1.9.6,we introduced this new utility to help developers setup their biped constraints swiftly.

This includes constraints to:

  • limit elbow to rotate in one plane, and limit the rotation angle;
  • limit knee to rotate in one plane, and limit the rotation angle;
  • limit shoulder's rotation range, and limit the twist range;
  • limit thigh's rotation range, and limit the twist range;

(By 'twist', we mean rotation around the primary axis, e.g.: shoulder to elbow axis)


1. get started

This utility can be brought up via the menu item at "Window/Skele/SetupBipedConstraint";

2. options 

(1) The first thing to do is to fill the "Root" field; you should put the topmost GameObject of model (usually with the Animator) in there.

This field is automatically filled for you if the model is selected when the EditorWindow is opened up;

(2) The "bones" list is a bone mapping table, it is automatically filled when the "Root" field is changed.

Usually you don't need to touch anything in the list, there're some special cases though, e.g.:

  • The skeleton structure is kind of unusual, and you might need to manually change the bone mapping here;
  • You don't want to setup constraints on some limbs, so you could try removing the hands references from the list;

(3) The "Options" will affect what kind of constraints be added to the model

  • If nothing is selected, constraints will be added on shoulder/elbow/thigh/knee, this is the basic setting, it improves the IK quality when manipulate the bones;
  • If 'Add IKTarget' is selected, besides the constraints above, IK-targets will be added at wrists & ankles. They enable devs to move the limbs by dragging the IK-target, without starting the SMREditor;
  • If 'Floor constraints' is selected, you need to specify another object as Floor(check the Floor constraints page), then the IK-targets on ankles will be constrainted to not go below the floor;
  • If 'Pelvis Follow' is selected, two 'CopyPosition' constraints will be added at the 'Hips' bone, to make it stay at the center position of two ankles' IK-targets. i.e.: the model will move with the two feet.


You could also check the tutorial video below for reference: