IKRootsHelper

import { HemisphereLight, MathUtils } from 'three';
import URDFLoader from 'urdf-loader';
import { Solver, Goal, IKRootsHelper, URDFUtils, IKUtils } from 'closed-chain-ik';

// scene, camera and renderer are initialized here

const URL = 'https://raw.githubusercontent.com/gkjohnson/urdf-loaders/master/urdf/T12/urdf/T12_flipped.URDF';

scene.add( new HemisphereLight( 0xffffff, 0x444444, 3 ) );
camera.position.set( 6, 5, 8 );

const robot = await new URDFLoader().loadAsync( URL );
robot.rotation.x = Math.PI / 2;
robot.position.y = 1.25;
for ( let i = 1; i <= 6; i ++ ) {

	robot.setJointValue( `HP${ i }`, MathUtils.degToRad( 30 ) );
	robot.setJointValue( `KP${ i }`, MathUtils.degToRad( 90 ) );
	robot.setJointValue( `AP${ i }`, MathUtils.degToRad( - 30 ) );

}

robot.updateMatrixWorld( true );
scene.add( robot );

const ik = URDFUtils.urdfRobotToIKRoot( robot );
URDFUtils.setIKFromUrdf( ik, robot );
IKUtils.saveRestPose( ik );

ik.traverse( frame => {

	if ( ! /^Foot/.test( frame.name ) ) return;

	const goal = new Goal();
	goal.makeClosure( frame );
	frame.getWorldPosition( goal.position );
	frame.getWorldQuaternion( goal.quaternion );
	goal.setMatrixNeedsUpdate();

} );

const body = ik.find( frame => frame.name === 'Body' );
const bodyGoal = new Goal();
bodyGoal.makeClosure( body );
body.getWorldQuaternion( bodyGoal.quaternion );

const start = [ 0, 0, 0 ];
body.getWorldPosition( start );

const helper = new IKRootsHelper( ik );
helper.setColor( 0xe91e63 );

const drawThroughHelper = new IKRootsHelper( ik );
drawThroughHelper.setColor( 0xe91e63 );
drawThroughHelper.setDrawThrough( true );
scene.add( helper, drawThroughHelper );

const solver = new Solver( ik );
renderer.setAnimationLoop( time => {

	const angle = time / 800;
	bodyGoal.setPosition( start[ 0 ] + 0.4 * Math.cos( angle ), start[ 1 ] + 0.35 * Math.sin( 2 * angle ), start[ 2 ] + 0.4 * Math.sin( angle ) );
	solver.solve();
	URDFUtils.setUrdfFromIK( robot, ik );
	renderer.render( scene, camera );

} );