So. at least this is running without new bugs.

helloqube/controller.cpp

 #include "controller.h"
 #include "myglwidget.h"
 #include "scenegraph.h"
+#include "primitive.h"
 
 Controller::Controller(QStatusBar*  bar)
 {
@@ -254,7 +255,7 @@ void Controller::deletePrimitive(){
 void Controller::selectTransform(RigidBodyTransformation *rbt){
     currentTransform = rbt;
     if (currentTransform){
-        statusBar->showMessage(currentTransform->getChild()->getName());
+        statusBar->showMessage(currentTransform->getChildPrimitive()->getName());
     }
     else {
         statusBar->showMessage("None selected");

helloqube/controller.h

@@ -16,6 +16,7 @@
 #include <QQuaternion>
 #include <QGridLayout>
 #include <rigidbodytransformation.h>
+#include <QStatusBar>
 
 #include <math.h>
 

helloqube/helloqube.pro

@@ -21,7 +21,9 @@ SOURCES += main.cpp\
     scenegraph.cpp \
     primitive.cpp \
     rigidbodytransformation.cpp \
-    controller.cpp
+    controller.cpp \
+    myitemmodel.cpp \
+    treeitem.cpp
 
 HEADERS  += mainwindow.h \
     myglwidget.h \
@@ -29,7 +31,9 @@ HEADERS  += mainwindow.h \
     primitive.h \
     rigidbodytransformation.h \
     controller.h \
-    glut.h
+    glut.h \
+    myitemmodel.h \
+    treeitem.h
 
 RESOURCES += \
     helloqube.qrc

helloqube/helloqube.pro.user

 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE QtCreatorProject>
-<!-- Written by QtCreator 3.5.1, 2015-11-21T21:18:46. -->
+<!-- Written by QtCreator 3.5.1, 2015-11-22T14:19:27. -->
 <qtcreator>
  <data>
   <variable>EnvironmentId</variable>

helloqube/myglwidget.cpp

 #include "myglwidget.h"
 #include "controller.h"
 #include "scenegraph.h"
+#include "primitive.h""
 
 //QGLShaderProgram *MyGLWidget::phongShader;
 
@@ -169,7 +170,7 @@ void MyGLWidget::paintGL(){
         glMultMatrixf(m.data());
 
         //draw primitive
-        Primitive* p = (*i)->getChild();
+        Primitive* p = (*i)->getChildPrimitive();
         int tesselation = p->getTesselation();
         Primitive::Type type = p->getType();
         qDebug() << "draw type " << type;

helloqube/myitemmodel.cpp

+#include "myitemmodel.h"
+
+MyItemModel::MyItemModel()
+{
+
+}
+

helloqube/myitemmodel.h

+#ifndef MYITEMMODEL_H
+#define MYITEMMODEL_H
+
+#include <QAbstractItemModel>
+
+class MyItemModel : public QAbstractItemModel
+{
+public:
+    MyItemModel();
+};
+
+#endif // MYITEMMODEL_H

helloqube/primitive.cpp

 #include "primitive.h"
+#include "rigidbodytransformation.h"
 
 Primitive::Primitive()
 {

helloqube/primitive.h

@@ -2,8 +2,11 @@
 #define PRIMITIVE_H
 
 #include <QtOpenGL>
+#include "treeitem.h"
 
-class Primitive
+class RigidBodyTransformation;
+
+class Primitive : public TreeItem
 {
 public:
 

helloqube/rigidbodytransformation.cpp

 #include "rigidbodytransformation.h"
+#include "primitive.h"
 
 RigidBodyTransformation::RigidBodyTransformation(Primitive* child)
 {
     translation = QVector3D(0,0,0);
     rotation = QQuaternion();
-    this->child = child;
+//    this->child = child;
+
+    children.append(child);
 //    qDebug() << "new rbt " << tx << "," << ty << "," << tz << ", rot " << rotation;
 }
 
 RigidBodyTransformation::~RigidBodyTransformation(){
-    child->~Primitive();
+//apparently I do not need to call the baseclass destructor.
 }
 
 
@@ -34,6 +37,9 @@ void RigidBodyTransformation::setRotation(QQuaternion newRotation){
     rotation = newRotation;
 }
 
-Primitive* RigidBodyTransformation::getChild(){
-    return child;
+Primitive* RigidBodyTransformation::getChildPrimitive(){
+    if (children.length() > 0){
+        return static_cast<Primitive*>(children[0]);//TODO aufpassen falls höhere tiefe
+    }
+    qDebug("WAAAH");
 }

helloqube/rigidbodytransformation.h

@@ -2,9 +2,11 @@
 #define RIGIDBODYTRANSFORMATION_H
 
 #include <QQuaternion>
-#include <primitive.h>
+#include <QDebug>
+#include "treeitem.h"
+class Primitive;
 
-class RigidBodyTransformation
+class RigidBodyTransformation : public TreeItem
 {
 public:
     RigidBodyTransformation(Primitive* child);
@@ -16,7 +18,7 @@ public:
 
     const QQuaternion getRotation();
     const QVector3D getTranslation();
-    Primitive* getChild();
+    Primitive* getChildPrimitive();
 
     void drawChild();
 
@@ -27,7 +29,7 @@ private :
     QQuaternion rotation;
 
     //child in scene graph
-    Primitive* child;
+    Primitive* childPrimitive;
 };
 
 #endif // RIGIDBODYTRANSFORMATION_H

helloqube/scenegraph.cpp

 #include "scenegraph.h"
 #include "myglwidget.h"
+#include "primitive.h"
 
 SceneGraph::SceneGraph()
 {

helloqube/scenegraph.h

@@ -3,6 +3,7 @@
 
 #include <QList>
 #include <rigidbodytransformation.h>
+#include <QString>
 
 class MyGLWidget;
 

helloqube/treeitem.cpp

+#include "treeitem.h"
+
+TreeItem::TreeItem()
+{
+    children = QList<TreeItem*>();
+}
+
+TreeItem::~TreeItem(){
+    while(children.length() > 0){
+        TreeItem* t = children[0];
+        children.removeAt(0);
+        t->~TreeItem();
+    }
+}
+
+void TreeItem::setParent(TreeItem *parent){
+    this->parent = parent;
+}
+
+TreeItem* TreeItem::getParent(){
+    return parent;
+}
+
+int TreeItem::getChildrenCount(){
+    return children.length();
+}
+
+//adds to child list AND sets itself as parent.
+void TreeItem::addChild(TreeItem *item){
+    children.append(item);
+    item->setParent(this);
+}
+
+//removes from children list. Does NOT delet child.
+bool TreeItem::removeChild(TreeItem *item){
+    return children.removeOne(item);
+}
+
+QList<TreeItem*> TreeItem::getChildren(){
+    return children;
+}
+
+TreeItem* TreeItem::getChild(int index){
+    if (index < children.length()){
+        return children[index];
+    }
+    return 0;
+}

helloqube/treeitem.h

+#ifndef TREEITEM_H
+#define TREEITEM_H
+
+#include <QList>
+#include <QDebug>
+
+class TreeItem
+{
+public:
+    TreeItem();
+    ~TreeItem();
+
+    TreeItem* getParent();
+    QList<TreeItem*> getChildren();
+    TreeItem* getChild(int index);//return 0 if index too large
+    int getChildrenCount();
+
+    void addChild(TreeItem* item);
+    bool removeChild(TreeItem* item);
+    void setParent(TreeItem* parent);
+
+protected:
+    TreeItem* parent;
+    QList<TreeItem*> children;
+};
+
+#endif // TREEITEM_H