From 38ae2822545700c0615a84551d472fe847f19b70 Mon Sep 17 00:00:00 2001
From: Kevin Rushforth <kcr@dev.java.net>
Date: Fri, 17 Sep 2004 20:18:20 +0000
Subject: Issue number:  73 Obtained from: herkules Submitted by:  kcr Reviewed
 by:   kcr Fix for Issue 73 (Quat4f#interpolate: incorrect when q1*q2<0)

git-svn-id: https://svn.java.net/svn/vecmath~svn/trunk@17 dd45e54d-f42e-c781-df72-dca083a658b1
---
 src/javax/vecmath/Quat4d.java | 10 ++++++----
 src/javax/vecmath/Quat4f.java | 10 ++++++----
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/src/javax/vecmath/Quat4d.java b/src/javax/vecmath/Quat4d.java
index c6232f6..835e8e7 100644
--- a/src/javax/vecmath/Quat4d.java
+++ b/src/javax/vecmath/Quat4d.java
@@ -601,11 +601,12 @@ public class Quat4d extends Tuple4d implements java.io.Serializable {
       dot = x*q1.x + y*q1.y + z*q1.z + w*q1.w;
 
       if ( dot < 0 ) {
-        // switch the quaterion values
+        // negate quaternion
         q1.x = -q1.x;  q1.y = -q1.y;  q1.z = -q1.z;  q1.w = -q1.w;
+        dot = -dot;
       }
 
-      if ( (1.0 - Math.abs(dot) ) > EPS ) {
+      if ( (1.0 - dot) > EPS ) {
         om = Math.acos(dot);
         sinom = Math.sin(om);
         s1 = Math.sin((1.0-alpha)*om)/sinom;
@@ -640,11 +641,12 @@ public class Quat4d extends Tuple4d implements java.io.Serializable {
       dot = q2.x*q1.x + q2.y*q1.y + q2.z*q1.z + q2.w*q1.w;
 
       if ( dot < 0 ) {
-        // switch the quaterion values
+        // negate quaternion
         q1.x = -q1.x;  q1.y = -q1.y;  q1.z = -q1.z;  q1.w = -q1.w;
+        dot = -dot;
       }
 
-      if ( (1.0 - Math.abs(dot) ) > EPS ) {
+      if ( (1.0 - dot) > EPS ) {
         om = Math.acos(dot);
         sinom = Math.sin(om);
         s1 = Math.sin((1.0-alpha)*om)/sinom;
diff --git a/src/javax/vecmath/Quat4f.java b/src/javax/vecmath/Quat4f.java
index f4fecfa..ecbef4b 100644
--- a/src/javax/vecmath/Quat4f.java
+++ b/src/javax/vecmath/Quat4f.java
@@ -606,11 +606,12 @@ public class Quat4f extends Tuple4f implements java.io.Serializable {
      dot = x*q1.x + y*q1.y + z*q1.z + w*q1.w;
 
      if ( dot < 0 ) {
-       // switch the quaterion values
+        // negate quaternion
        q1.x = -q1.x;  q1.y = -q1.y;  q1.z = -q1.z;  q1.w = -q1.w;
+       dot = -dot;
      }
 
-     if ( (1.0 - Math.abs(dot) ) > EPS ) {
+     if ( (1.0 - dot) > EPS ) {
        om = Math.acos(dot);
        sinom = Math.sin(om);
        s1 = Math.sin((1.0-alpha)*om)/sinom;
@@ -648,11 +649,12 @@ public class Quat4f extends Tuple4f implements java.io.Serializable {
      dot = q2.x*q1.x + q2.y*q1.y + q2.z*q1.z + q2.w*q1.w;
      
      if ( dot < 0 ) {
-       // switch the quaterion values
+        // negate quaternion
        q1.x = -q1.x;  q1.y = -q1.y;  q1.z = -q1.z;  q1.w = -q1.w;
+       dot = -dot;
      }
 
-     if ( (1.0 - Math.abs(dot) ) > EPS ) {
+     if ( (1.0 - dot) > EPS ) {
        om = Math.acos(dot);
        sinom = Math.sin(om);
        s1 = Math.sin((1.0-alpha)*om)/sinom;
-- 
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