Created
October 15, 2012 09:22
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Solve simple IK for character legs on differing ground height for Unity3D.
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function LateUpdate () { | |
if ( collision.grounded ) { | |
IKOn = true; | |
} | |
else { | |
IKOn = false; | |
} | |
ik.solveLegIK (); | |
} |
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// Define bones. | |
private var rootBone : Transform; | |
private var pelvis : Transform; | |
private var leftThigh : Transform; | |
private var leftCalf : Transform; | |
private var leftFoot : Transform; | |
private var rightThigh : Transform; | |
private var rightCalf : Transform; | |
private var rightFoot : Transform; | |
private var leftThighLength : float; | |
private var rightThighLength : float; | |
private var leftCalfLength : float; | |
private var rightCalfLength : float; | |
private var leftLegLength : float; | |
private var rightLegLength : float; | |
// Define offsets. | |
private var animationOffset : float = 0.01; // Difference between feet height in the animation that determines a dominant foot (i.e. foot that's taking the load whilst walking). | |
private var ankleHeightL : float = 0.0; | |
private var ankleHeightR : float = 0.0; | |
private var rootOffset : float = 0.0; | |
private var targetHeight : float = 0.0; | |
private var prevTargetHeight : float = 0.0; | |
// Foot states. | |
private var leftDown : boolean = false; | |
private var rightDown : boolean = false; | |
private var leftCollide : boolean = false; | |
private var rightCollide : boolean = false; | |
// Components. | |
private var characterMotor : characterMotor; | |
function Awake () { | |
rootBone = transform.Find ( "Bip001" ); | |
pelvis = rootBone.Find ( "Bip001 Pelvis" ); | |
leftThigh = pelvis.Find ( "Bip001 L Thigh" ); | |
leftCalf = leftThigh.Find ( "Bip001 L Calf" ); | |
leftFoot = leftCalf.Find ( "Bip001 L Foot" ); | |
rightThigh = pelvis.Find ( "Bip001 R Thigh" ); | |
rightCalf = rightThigh.Find ( "Bip001 R Calf" ); | |
rightFoot = rightCalf.Find ( "Bip001 R Foot" ); | |
leftThighLength = Vector3.Distance ( leftThigh.position, leftCalf.position ); | |
leftCalfLength = Vector3.Distance ( leftCalf.position, leftFoot.position ); | |
leftLegLength = leftThighLength + leftCalfLength; | |
rightThighLength = Vector3.Distance ( rightThigh.position, rightCalf.position ); | |
rightCalfLength = Vector3.Distance ( rightCalf.position, rightFoot.position ); | |
rightLegLength = rightThighLength + rightCalfLength; | |
prevTargetHeight = rootBone.position.y; | |
characterMotor = transform.GetComponent ( "characterMotor" ) as characterMotor; | |
} | |
public function solveLegIK () { | |
if ( characterMotor.IKOn ) { | |
rootOffset = rootBone.position.y - transform.position.y; | |
ankleHeightL = leftFoot.position.y - transform.position.y; | |
ankleHeightR = rightFoot.position.y - transform.position.y; | |
// Default feet targets. | |
var leftGround = leftFoot.position; | |
var rightGround = rightFoot.position; | |
var originalLeftGround = leftFoot.position; | |
var originalRightGround = rightFoot.position; | |
//Debug.DrawLine(leftGround, rightGround, Color.white); | |
// Are we walking in the animation? | |
// i.e. Is there a height difference between the feet in the animation. If so, which foot - if either - should be planted on the ground? | |
var animationDelta = leftGround.y - rightGround.y; | |
if ( animationDelta < -animationOffset ) { | |
leftDown = true; | |
rightDown = false; | |
} else if ( animationDelta > animationOffset ) { | |
leftDown = false; | |
rightDown = true; | |
} else { | |
leftDown = true; | |
rightDown = true; | |
} | |
// Raycast check to see if we're through collision and set the target points accordingly. | |
// If we're not, then we keep the positions as defined in the animation. | |
var hit : RaycastHit; | |
var rayDistance : float = 0.0; | |
// If right is dominant foot, check to see if the left foot is colliding as well. | |
if ( ( !leftDown ) && ( rightDown ) ) { | |
rayDistance = leftCalfLength + ankleHeightL; | |
} else { | |
rayDistance = leftCalfLength + leftLegLength; | |
} | |
if ( rayDistance > 0 ) { | |
//Debug.DrawRay(leftFoot.position + Vector3(0,leftCalfLength,0), -Vector3.up * rayDistance, Color.magenta); | |
if ( Physics.Raycast ( leftFoot.position + Vector3 ( 0, leftCalfLength, 0 ), -Vector3.up, hit, rayDistance ) ) { | |
if ( hit.point.y + ankleHeightL < leftFoot.position.y ) { | |
//Debug.DrawRay(leftFoot.position + Vector3(0,leftCalfLength,0), -Vector3.up * hit.distance, Color.blue); | |
leftGround = hit.point + Vector3 ( 0, ankleHeightL, 0 ); | |
} | |
} | |
} | |
// If left is dominant foot, check to see if the right foot is colliding as well. | |
if ( ( leftDown ) && ( !rightDown ) ) { | |
rayDistance = rightCalfLength + ankleHeightR; | |
} else { | |
rayDistance = rightCalfLength + rightLegLength; | |
} | |
if ( rayDistance > 0 ) { | |
//Debug.DrawRay(rightFoot.position + Vector3(0,leftCalfLength,0), -Vector3.up * rayDistance, Color.magenta); | |
if ( Physics.Raycast ( rightFoot.position + Vector3 ( 0, rightCalfLength, 0 ), -Vector3.up, hit, rayDistance ) ) { | |
if ( hit.point.y + ankleHeightR < rightFoot.position.y ) { | |
//Debug.DrawRay(rightFoot.position + Vector3(0,rightCalfLength,0), -Vector3.up * hit.distance, Color.blue); | |
rightGround = hit.point + Vector3( 0, ankleHeightR, 0 ); | |
} | |
} | |
} | |
// Work out which legs are grounded, or if the distance to floor is such that both should be. | |
// Run IK on those legs. | |
if ( ( leftDown ) && ( !rightDown ) ) { // Left foot is down. | |
targetHeight = leftGround.y - ankleHeightL + rootOffset; | |
} | |
else if ( ( !leftDown ) && ( rightDown ) ) { // Right foot is down. | |
targetHeight = rightGround.y - ankleHeightR + rootOffset; | |
} | |
else { | |
// Both feet are more or less equal in the animation - both should be considered as being on the ground. | |
// So move down to lowest foot and do the IK from there. | |
if ( leftGround.y < rightGround.y ) { | |
targetHeight = leftGround.y - ankleHeightL + rootOffset; | |
} | |
else { | |
targetHeight = rightGround.y - ankleHeightR + rootOffset; | |
} | |
} | |
// Move the root bone - if we move the transform, it'll fall through the world. | |
// Quickly lerp it's movement for a smoother transition - looks very snappy otherwise. | |
// Currently 1/8 second. | |
targetHeight = Mathf.Lerp ( prevTargetHeight, targetHeight, Time.deltaTime * 8 ); | |
var heightDiff = targetHeight - rootBone.position.y; | |
rootBone.position.y = targetHeight; | |
prevTargetHeight = rootBone.position.y; | |
// Fix position for unmoved foot, as we've moved the root bone down. | |
// Otherwise the foot tries to go to it's original point in worldspace, not it's new one. | |
if ( ( !leftDown ) && ( rightDown ) && ( leftGround == originalLeftGround ) ) { | |
leftGround.y += heightDiff; | |
} | |
if ( ( leftDown ) && ( !rightDown ) && ( rightGround == originalRightGround ) ) { | |
rightGround.y += heightDiff; | |
} | |
// Solve IK. | |
// Expects 3DS Max FBX bones that are rotated 270 on X. | |
IKSolve ( leftThigh, leftCalf, leftFoot, leftGround ); | |
IKSolve ( rightThigh, rightCalf, rightFoot, rightGround ); | |
} | |
else { | |
prevTargetHeight = rootBone.position.y; | |
} | |
} | |
function IKSolve ( start : Transform, mid : Transform, end : Transform, target : Vector3 ) { | |
var startEndAxis = Vector3.Normalize ( end.position - start.position ); | |
var startEndDist = Vector3.Distance ( start.position, end.position ); | |
var startTargetAxis = Vector3.Normalize ( target - start.position ); | |
var startTargetDist = Vector3.Distance ( start.position, target ); | |
var startMidDist = Vector3.Distance ( start.position, mid.position ); | |
var midEndDist = Vector3.Distance ( mid.position, end.position ); | |
var midAngle = Mathf.Acos ( ( startMidDist * startMidDist + midEndDist * midEndDist - startEndDist * startEndDist ) / ( 2 * startMidDist * midEndDist ) ) * Mathf.Rad2Deg; | |
if ( startTargetDist > ( startMidDist + midEndDist ) ) { | |
// If the target's too far away, aim to reach as far as the leg can go. | |
// Minus a tiny amount to account for floating point inaccuracy. It'll start throwing NaNs if you don't have this. | |
startTargetDist = startMidDist + midEndDist - 0.01; | |
} | |
var newMidAngle = Mathf.Acos ( ( startMidDist * startMidDist + midEndDist * midEndDist - startTargetDist * startTargetDist ) / ( 2 * startMidDist * midEndDist ) ) * Mathf.Rad2Deg; | |
var rotateAngle = ( newMidAngle - midAngle ) * 0.5; | |
// Check it's not using rubbish data, otherwise it'll throw errors. | |
if ( !float.IsNaN ( rotateAngle ) ) { | |
start.RotateAround ( start.position, start.forward, rotateAngle ); | |
mid.RotateAround ( mid.position, mid.forward, -1 * rotateAngle * 2 ); | |
} | |
} |
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Is there any way to see how this is supposed to be set up on a character? I cannot seem to get it working properly.