1 files changed, 26 insertions, 11 deletions
diff --git a/src/ui/accelerometercontrol.cpp b/src/ui/accelerometercontrol.cpp
index 03ed36a..d4656f6 100644
--- a/src/ui/accelerometercontrol.cpp
+++ b/src/ui/accelerometercontrol.cpp
@@ -40,28 +40,33 @@
 #include <QtGui/QMatrix4x4>
 #include <QtGui/QMouseEvent>
 
+static QVector3D accelerometerX(-1, 0, 0);
+static QVector3D accelerometerY(0, 1, 0);
+static QVector3D accelerometerZ(0, 0, -1);
+static QVector3D unrotatedGravity(0, 1, 0);
+
 AccelerometerControl::AccelerometerControl(QWidget *parent)
-    : QGLWidget(parent)
+    : QGLWidget(parent), mGravity(9.8)
 {
 }
 
-void AccelerometerControl::setValue(const QVector3D &value)
+void AccelerometerControl::setValue(const QVector3D &newValue)
 {
-    QVector3D up(0, 1, 0);
-    QVector3D target = value.normalized();
+    mGravity = newValue.length();
+    QVector3D target = newValue.normalized();
+
+    if ((newValue - value()).lengthSquared() < 0.0001)
+        return;
 
-    qreal dot = QVector3D::dotProduct(up, target);
+    qreal dot = QVector3D::dotProduct(accelerometerY, target);
     if (dot > 0.999) {
         mRotation = QQuaternion();
-        mUpValue = value;
     } else if(dot < -0.999) {
         mRotation = QQuaternion::fromAxisAndAngle(0, 0, 1, 180);
-        mUpValue = -value;
     } else {
         // we want the quaternion that transforms target into up
-        QVector3D cross = QVector3D::crossProduct(target, up);
+        QVector3D cross = QVector3D::crossProduct(target, accelerometerY);
         mRotation = QQuaternion::fromAxisAndAngle(cross, qAcos(dot) * 180 / M_PI);
-        mUpValue = mRotation.rotatedVector(value);
     }
 
     updateGL();
@@ -263,8 +268,7 @@ void AccelerometerControl::mouseMoveEvent(QMouseEvent *event)
     }
     mOldMousePosition = event->pos();
 
-    QVector3D newValue = mRotation.conjugate().rotatedVector(mUpValue);
-    emit valueChanged(newValue);
+    emit valueChanged(value());
     updateGL();
 }
 
@@ -293,3 +297,14 @@ void AccelerometerControl::setDeviceOrientation(bool portrait)
     }
     updateGL();
 }
+
+QVector3D AccelerometerControl::value() const
+{
+    QVector3D newValue;
+    newValue.setX(QVector3D::dotProduct(mRotation.conjugate().rotatedVector(accelerometerX), unrotatedGravity));
+    newValue.setY(QVector3D::dotProduct(mRotation.conjugate().rotatedVector(accelerometerY), unrotatedGravity));
+    newValue.setZ(QVector3D::dotProduct(mRotation.conjugate().rotatedVector(accelerometerZ), unrotatedGravity));
+    newValue *= mGravity;
+
+    return newValue;
+}