Introduce QQuaternion::dotProduct()

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

src/gui/math3d/qquaternion.cpp

@@ -212,10 +212,19 @@ QT_BEGIN_NAMESPACE
     \sa scalar(), setX(), setY(), setZ()
 */
 
+/*!
+    \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();

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.

tests/auto/gui/math3d/qquaternion/tst_qquaternion.cpp

@@ -45,6 +45,9 @@ public:
 private slots:
     void create();
 
+    void dotProduct_data();
+    void dotProduct();
+
     void length_data();
     void length();
 
@@ -219,6 +222,58 @@ void tst_QQuaternion::create()
     QCOMPARE(v10.w(), 34.0f);
 }
 
+// Test the computation of dot product.
+void tst_QQuaternion::dotProduct_data()
+{
+    QTest::addColumn<float>("x1");
+    QTest::addColumn<float>("y1");
+    QTest::addColumn<float>("z1");
+    QTest::addColumn<float>("scalar1");
+    QTest::addColumn<float>("x2");
+    QTest::addColumn<float>("y2");
+    QTest::addColumn<float>("z2");
+    QTest::addColumn<float>("scalar2");
+    QTest::addColumn<float>("dot");
+
+    QTest::newRow("null")
+        << 0.0f << 0.0f << 0.0f << 0.0f
+        << 0.0f << 0.0f << 0.0f << 0.0f
+        << 0.0f;
+
+    QTest::newRow("identity")
+        << 0.0f << 0.0f << 0.0f << 1.0f
+        << 0.0f << 0.0f << 0.0f << 1.0f
+        << 1.0f;
+
+    QTest::newRow("unitvec")
+        << 1.0f << 0.0f << 0.0f << 0.0f
+        << 0.0f << 1.0f << 0.0f << 0.0f
+        << 0.0f;
+
+    QTest::newRow("complex")
+        << 1.0f << 2.0f << 3.0f << 4.0f
+        << 4.0f << 5.0f << 6.0f << 7.0f
+        << 60.0f;
+}
+void tst_QQuaternion::dotProduct()
+{
+    QFETCH(float, x1);
+    QFETCH(float, y1);
+    QFETCH(float, z1);
+    QFETCH(float, scalar1);
+    QFETCH(float, x2);
+    QFETCH(float, y2);
+    QFETCH(float, z2);
+    QFETCH(float, scalar2);
+    QFETCH(float, dot);
+
+    QQuaternion q1(scalar1, x1, y1, z1);
+    QQuaternion q2(scalar2, x2, y2, z2);
+
+    QCOMPARE(QQuaternion::dotProduct(q1, q2), dot);
+    QCOMPARE(QQuaternion::dotProduct(q2, q1), dot);
+}
+
 // Test length computation for quaternions.
 void tst_QQuaternion::length_data()
 {