Introduce QQuaternion::dotProduct()

Change-Id: I14b9857ca0a43808b7d536fc258a6bb10f611211
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@theqtcompany.com>

2 files changed, 27 insertions, 17 deletions

diff --git a/src/gui/math3d/qquaternion.cpp b/src/gui/math3d/qquaternion.cpp
index 4f07d82a25..141651eda1 100644
--- a/src/gui/math3d/qquaternion.cpp
+++ b/src/gui/math3d/qquaternion.cpp
@@ -213,9 +213,18 @@ QT_BEGIN_NAMESPACE
 */
 
 /*!
+    \fn float QQuaternion::dotProduct(const QQuaternion &q1, const QQuaternion &q2)
+    \since 5.5
+
+    Returns the dot product of \a q1 and \a q2.
+
+    \sa length()
+*/
+
+/*!
     Returns the length of the quaternion.  This is also called the "norm".
 
-    \sa lengthSquared(), normalized()
+    \sa lengthSquared(), normalized(), dotProduct()
 */
 float QQuaternion::length() const
 {
@@ -225,7 +234,7 @@ float QQuaternion::length() const
 /*!
     Returns the squared length of the quaternion.
 
-    \sa length()
+    \sa length(), dotProduct()
 */
 float QQuaternion::lengthSquared() const
 {
@@ -240,7 +249,7 @@ float QQuaternion::lengthSquared() const
     will be returned as-is.  Otherwise the normalized form of the
     quaternion of length 1 will be returned.
 
-    \sa length(), normalize()
+    \sa normalize(), length(), dotProduct()
 */
 QQuaternion QQuaternion::normalized() const
 {
@@ -792,13 +801,10 @@ QQuaternion QQuaternion::slerp
         return q2;
 
     // Determine the angle between the two quaternions.
-    QQuaternion q2b;
-    float dot;
-    dot = q1.xp * q2.xp + q1.yp * q2.yp + q1.zp * q2.zp + q1.wp * q2.wp;
-    if (dot >= 0.0f) {
-        q2b = q2;
-    } else {
-        q2b = -q2;
+    QQuaternion q2b(q2);
+    float dot = QQuaternion::dotProduct(q1, q2);
+    if (dot < 0.0f) {
+        q2b = -q2b;
         dot = -dot;
     }
 
@@ -844,13 +850,10 @@ QQuaternion QQuaternion::nlerp
         return q2;
 
     // Determine the angle between the two quaternions.
-    QQuaternion q2b;
-    float dot;
-    dot = q1.xp * q2.xp + q1.yp * q2.yp + q1.zp * q2.zp + q1.wp * q2.wp;
-    if (dot >= 0.0f)
-        q2b = q2;
-    else
-        q2b = -q2;
+    QQuaternion q2b(q2);
+    float dot = QQuaternion::dotProduct(q1, q2);
+    if (dot < 0.0f)
+        q2b = -q2b;
 
     // Perform the linear interpolation.
     return (q1 * (1.0f - t) + q2b * t).normalized();
diff --git a/src/gui/math3d/qquaternion.h b/src/gui/math3d/qquaternion.h
index a02c37ce1d..b4022e8579 100644
--- a/src/gui/math3d/qquaternion.h
+++ b/src/gui/math3d/qquaternion.h
@@ -78,6 +78,8 @@ public:
     void setZ(float z);
     void setScalar(float scalar);
 
+    Q_DECL_CONSTEXPR static inline float dotProduct(const QQuaternion &q1, const QQuaternion &q2);
+
     float length() const;
     float lengthSquared() const;
 
@@ -168,6 +170,11 @@ inline void QQuaternion::setY(float aY) { yp = aY; }
 inline void QQuaternion::setZ(float aZ) { zp = aZ; }
 inline void QQuaternion::setScalar(float aScalar) { wp = aScalar; }
 
+Q_DECL_CONSTEXPR inline float QQuaternion::dotProduct(const QQuaternion &q1, const QQuaternion &q2)
+{
+    return q1.xp * q2.xp + q1.yp * q2.yp + q1.zp * q2.zp + q1.wp * q2.wp;
+}
+
 inline QQuaternion QQuaternion::inverted() const
 {
     // Need some extra precision if the length is very small.