Add inverseBindMatrix property to QJoint

Needed to compute skinning palette of matrices.

Change-Id: Ifec41c2bb18855bbb2c332cf80d37642d34f75cf
Reviewed-by: Paul Lemire <paul.lemire@kdab.com>

3 files changed, 43 insertions, 0 deletions

diff --git a/src/core/transforms/qjoint.cpp b/src/core/transforms/qjoint.cpp
index ca5f6dff0..c83b1e530 100644
--- a/src/core/transforms/qjoint.cpp
+++ b/src/core/transforms/qjoint.cpp
@@ -51,6 +51,7 @@ namespace Qt3DCore {
 
 QJointPrivate::QJointPrivate()
     : QNodePrivate()
+    , m_inverseBindMatrix()
     , m_rotation()
     , m_translation()
     , m_scale(1.0f, 1.0f, 1.0f)
@@ -90,6 +91,15 @@ QJointPrivate::QJointPrivate()
 */
 
 /*!
+    \qmlproperty matrix4x4 inverseBindMatrix
+
+    Holds the inverse bind matrix of the joint. This is used to transform
+    vertices from model space into the space of this joint so they can
+    subsequently be multiplied by the joint's global transform to perform
+    the skinning operation.
+*/
+
+/*!
     \class Qt3DCore::QJoint
     \inmodule Qt3DCore
     \inherits Qt3DCore::QNode
@@ -148,6 +158,20 @@ QVector3D QJoint::translation() const
     return d->m_translation;
 }
 
+/*!
+    \property Qt3DCore::QJoint::inverseBindMatrix
+
+    Holds the inverse bind matrix of the joint. This is used to transform
+    vertices from model space into the space of this joint so they can
+    subsequently be multiplied by the joint's global transform to perform
+    the skinning operation.
+*/
+QMatrix4x4 QJoint::inverseBindMatrix() const
+{
+    Q_D(const QJoint);
+    return d->m_inverseBindMatrix;
+}
+
 void QJoint::setScale(const QVector3D &scale)
 {
     Q_D(QJoint);
@@ -178,6 +202,16 @@ void QJoint::setTranslation(const QVector3D &translation)
     emit translationChanged(translation);
 }
 
+void QJoint::setInverseBindMatrix(const QMatrix4x4 &inverseBindMatrix)
+{
+    Q_D(QJoint);
+    if (d->m_inverseBindMatrix == inverseBindMatrix)
+        return;
+
+    d->m_inverseBindMatrix = inverseBindMatrix;
+    emit inverseBindMatrixChanged(inverseBindMatrix);
+}
+
 /*!
     Adds \a joint as a child of this joint. If \a joint has no parent, then
     this joint takes ownership of it. Child joints are in the coordinate system
@@ -240,6 +274,7 @@ Qt3DCore::QNodeCreatedChangeBasePtr QJoint::createNodeCreationChange() const
     auto creationChange = Qt3DCore::QNodeCreatedChangePtr<QJointData>::create(this);
     auto &data = creationChange->data;
     Q_D(const QJoint);
+    data.inverseBindMatrix = d->m_inverseBindMatrix;
     data.childJointIds = qIdsForNodes(d->m_childJoints);
     data.rotation = d->m_rotation;
     data.scale = d->m_scale;
diff --git a/src/core/transforms/qjoint.h b/src/core/transforms/qjoint.h
index 35b559f59..024c83ec7 100644
--- a/src/core/transforms/qjoint.h
+++ b/src/core/transforms/qjoint.h
@@ -43,6 +43,7 @@
 #include <Qt3DCore/qnode.h>
 #include <Qt3DCore/qt3dcore_global.h>
 
+#include <QtGui/qmatrix4x4.h>
 #include <QtGui/qquaternion.h>
 #include <QtGui/qvector3d.h>
 
@@ -58,6 +59,7 @@ class QT3DCORESHARED_EXPORT QJoint : public QNode
     Q_PROPERTY(QVector3D scale READ scale WRITE setScale NOTIFY scaleChanged)
     Q_PROPERTY(QQuaternion rotation READ rotation WRITE setRotation NOTIFY rotationChanged)
     Q_PROPERTY(QVector3D translation READ translation WRITE setTranslation NOTIFY translationChanged)
+    Q_PROPERTY(QMatrix4x4 inverseBindMatrix READ inverseBindMatrix WRITE setInverseBindMatrix NOTIFY inverseBindMatrixChanged)
 
 public:
     explicit QJoint(Qt3DCore::QNode *parent = nullptr);
@@ -66,6 +68,7 @@ public:
     QVector3D scale() const;
     QQuaternion rotation() const;
     QVector3D translation() const;
+    QMatrix4x4 inverseBindMatrix() const;
 
     void addChildJoint(QJoint *joint);
     void removeChildJoint(QJoint *joint);
@@ -75,11 +78,13 @@ public Q_SLOTS:
     void setScale(const QVector3D &scale);
     void setRotation(const QQuaternion &rotation);
     void setTranslation(const QVector3D &translation);
+    void setInverseBindMatrix(const QMatrix4x4 &inverseBindMatrix);
 
 Q_SIGNALS:
     void scaleChanged(const QVector3D &scale);
     void rotationChanged(const QQuaternion &rotation);
     void translationChanged(const QVector3D &translation);
+    void inverseBindMatrixChanged(const QMatrix4x4 &inverseBindMatrix);
 
 private:
     Q_DECLARE_PRIVATE(QJoint)
diff --git a/src/core/transforms/qjoint_p.h b/src/core/transforms/qjoint_p.h
index 35915a7dd..a0d59eac4 100644
--- a/src/core/transforms/qjoint_p.h
+++ b/src/core/transforms/qjoint_p.h
@@ -52,6 +52,7 @@
 //
 
 #include <Qt3DCore/private/qnode_p.h>
+#include <Qt3DCore/qjoint.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -66,6 +67,7 @@ public:
 
     Q_DECLARE_PUBLIC(QJoint)
 
+    QMatrix4x4 m_inverseBindMatrix;
     QVector<QJoint *> m_childJoints;
     QQuaternion m_rotation;
     QVector3D m_translation;
@@ -74,6 +76,7 @@ public:
 
 struct QJointData
 {
+    QMatrix4x4 inverseBindMatrix;
     QNodeIdVector childJointIds;
     QQuaternion rotation;
     QVector3D translation;