Update skinned mesh example to expose joints of object

To do this we add a helper Sqt struct that wraps up an affine
transformation as a scale vector, rotation quaternion and a
translation vector. This is the format in which the animation
aspect will animate the joints later so it's easier to keep
the transforms split like this. It's also less data to move
around compared with a 4x4 matrix (10 vs 16 floats, 12 including
the padding).

Change-Id: Iaa30b5ef5d1635cc208ead918827140cf2765908
Reviewed-by: Paul Lemire <paul.lemire@kdab.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/src/core/transforms/qmath3d_p.h b/src/core/transforms/qmath3d_p.h
index 8c2afac31..a4f33f0b6 100644
--- a/src/core/transforms/qmath3d_p.h
+++ b/src/core/transforms/qmath3d_p.h
@@ -53,6 +53,7 @@
 #include <QtGui/qmatrix4x4.h>
 #include <QtGui/qquaternion.h>
 #include <QtGui/qvector3d.h>
+#include <Qt3DCore/private/sqt_p.h>
 
 #include <cmath>
 
@@ -189,6 +190,24 @@ inline void decomposeQMatrix4x4(const QMatrix4x4 &m, QVector3D &position, QQuate
     position = QVector3D(m(0, 3), m(1, 3), m(2, 3));
 }
 
+inline void decomposeQMatrix4x4(const QMatrix4x4 &m, Qt3DCore::Sqt &sqt)
+{
+    Q_ASSERT(m.isAffine());
+
+    const QMatrix3x3 m3x3(m.toGenericMatrix<3, 3>());
+
+    QMatrix3x3 rot3x3(Qt::Uninitialized);
+    if (hasScale(m)) {
+        decomposeQMatrix3x3(m3x3, rot3x3, sqt.scale, sqt.translation);
+    } else {
+        // we know there is no scaling part; no need for QDU decomposition
+        sqt.scale = QVector3D(1.0f, 1.0f, 1.0f);
+        rot3x3 = m3x3;
+    }
+    sqt.rotation = QQuaternion::fromRotationMatrix(rot3x3);
+    sqt.translation = QVector3D(m(0, 3), m(1, 3), m(2, 3));
+}
+
 QT_END_NAMESPACE
 
 #endif // QT3DCORE_QMATH3D_P_H