From 20d95080f1c0a6a252e1ee7e4364451c93db672c Mon Sep 17 00:00:00 2001
From: "Anthony J. Thibault" <tony@highfidelity.io>
Date: Thu, 5 Nov 2015 12:03:45 -0800
Subject: [PATCH] IK fix for avatars exported from Blender

This should fix the issue with the hips moving erratically when arm IK
is enabled.  The main issue is that the IK system assumed that the "Hips"
joint was the root of the skeleton.  For Blender avatar this is not the case
as it inserts an "Armature" node at the root instead.
---
 libraries/animation/src/AnimInverseKinematics.cpp | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/libraries/animation/src/AnimInverseKinematics.cpp b/libraries/animation/src/AnimInverseKinematics.cpp
index 42e9472819..6355426dae 100644
--- a/libraries/animation/src/AnimInverseKinematics.cpp
+++ b/libraries/animation/src/AnimInverseKinematics.cpp
@@ -156,11 +156,11 @@ void AnimInverseKinematics::solveWithCyclicCoordinateDescent(const std::vector<I
             // cache tip absolute transform
             int tipIndex = target.getIndex();
             int pivotIndex = _skeleton->getParentIndex(tipIndex);
-            if (pivotIndex == -1) {
+            if (pivotIndex == -1 || pivotIndex == _hipsIndex) {
                 continue;
             }
             int pivotsParentIndex = _skeleton->getParentIndex(pivotIndex);
-            if (pivotsParentIndex == -1) {
+            if (pivotsParentIndex == -1 || pivotIndex == _hipsIndex) {
                 // TODO?: handle case where tip's parent is root?
                 continue;
             }
@@ -173,7 +173,7 @@ void AnimInverseKinematics::solveWithCyclicCoordinateDescent(const std::vector<I
             glm::quat tipParentRotation = absolutePoses[pivotIndex].rot;
 
             // descend toward root, pivoting each joint to get tip closer to target
-            while (pivotsParentIndex != -1) {
+            while (pivotsParentIndex != _hipsIndex && pivotsParentIndex != -1) {
                 // compute the two lines that should be aligned
                 glm::vec3 jointPosition = absolutePoses[pivotIndex].trans;
                 glm::vec3 leverArm = tipPosition - jointPosition;
@@ -285,7 +285,7 @@ void AnimInverseKinematics::solveWithCyclicCoordinateDescent(const std::vector<I
         // only update the absolutePoses that need it: those between lowestMovedIndex and _maxTargetIndex
         for (int i = lowestMovedIndex; i <= _maxTargetIndex; ++i) {
             int parentIndex = _skeleton->getParentIndex(i);
-            if (parentIndex != -1) {
+            if (parentIndex != -1 && parentIndex != _hipsIndex) {
                 absolutePoses[i] = absolutePoses[parentIndex] * _relativePoses[i];
             }
         }
@@ -295,7 +295,7 @@ void AnimInverseKinematics::solveWithCyclicCoordinateDescent(const std::vector<I
     for (auto& target: targets) {
         int tipIndex = target.getIndex();
         int parentIndex = _skeleton->getParentIndex(tipIndex);
-        if (parentIndex != -1) {
+        if (parentIndex != -1 && parentIndex != _hipsIndex) {
             const glm::quat& targetRotation = target.getRotation();
             // compute tip's new parent-relative rotation
             // Q = Qp * q   -->   q' = Qp^ * Q