diff --git a/src/engine.cpp b/src/engine.cpp
index 0abb007..f11f9fb 100644
--- a/src/engine.cpp
+++ b/src/engine.cpp
@@ -30,7 +30,6 @@ Engine::Engine() :
     m_clock = new sf::Clock();
     m_clock->restart();
     m_renderer = new SparrowRenderer();
-    m_guiTools = new GuiTools(this);
 }
 
 Engine::~Engine()
@@ -65,6 +64,7 @@ void Engine::createWindow(std::string title,
     m_input = new Input(m_window);
     m_renderer->initGL(w, h);
     m_sparrowshell = new SparrowShell(m_window);
+    m_guiTools = new GuiTools();
 }
 
 void Engine::initPhysics()
@@ -118,8 +118,6 @@ void Engine::update()
             ImGui::End();
         }
 	}
-
-    m_guiTools->update();
 	
     // update Physics
     if(m_world != nullptr)
@@ -134,6 +132,7 @@ void Engine::update()
 
     // update Scene
     getScene()->update();
+    getScene()->updateShaders();
 
     // update Display
     if(m_input->isResized())
@@ -181,10 +180,13 @@ void Engine::setScene(std::string scene)
     }
 
     previous_scene->getRootObject()->removeChild(m_sparrowshell);
+    previous_scene->getRootObject()->removeChild(m_guiTools);
+
     m_renderer->setScene(new_scene);
     m_renderer->resizeGL(m_window->getSize().x, m_window->getSize().y);
+
     new_scene->getRootObject()->addChild(m_sparrowshell);
-    new_scene->updateShaders();
+    new_scene->getRootObject()->addChild(m_guiTools);
 }
 
 void Engine::enablePhysicsDebug()
@@ -195,7 +197,6 @@ void Engine::enablePhysicsDebug()
         getScene()->addToIndex(m_physicsDebugNode);
         m_world->setDebugDrawer(m_physicsDebugNode);
         m_world->getDebugDrawer()->setDebugMode(btIDebugDraw::DBG_DrawWireframe);
-        getScene()->updateShaders();
     }
 }
 
@@ -269,7 +270,7 @@ void Engine::checkSpecialInputs()
 
 void Engine::createScene(std::string scene_name)
 {
-    RESOURCE_ADD(new SceneTree(*this),SceneTree,scene_name);
+    RESOURCE_ADD(new SceneTree(*this), SceneTree, scene_name);
     //return new SceneTree(*this);
 }
 
diff --git a/src/guitools.cpp b/src/guitools.cpp
index 883b3ba..a431ddd 100644
--- a/src/guitools.cpp
+++ b/src/guitools.cpp
@@ -2,51 +2,28 @@
 #include "imgui/imgui.h"
 
 #include "engine.h"
+#include "tools/scenepicker.h"
 #include "scene/scenetree.h"
-#include "SparrowRenderer/deferredpipeline.h"
-#include "scene/playercharacternode.h"
 
-#include <btBulletCollisionCommon.h>
-#include <btBulletDynamicsCommon.h>
-#include <BulletDynamics/Character/btKinematicCharacterController.h>
-
-GuiTools::GuiTools(Engine* engine) :
-    m_engine(engine),
+GuiTools::GuiTools() :
+    m_pickerNode(new ScenePicker()),
     m_pickerEnabled(false)
 {
-
+    addChild(m_pickerNode);
+    m_pickerNode->setVisible(false);
 }
 
 void GuiTools::update()
 {
+    // no automatic update of children, we want to update them manually
+    // ContainerNode::update();
+
     if(m_pickerEnabled)
-    {
-        DeferredPipeline* pip = (DeferredPipeline*) m_engine->getScene()->getPipeline();
-        FirstPersonCamera* cam = (FirstPersonCamera*) pip->getCamera();
-        glm::vec3 dir_cam = cam->getDirection()*100;
-        btVector3 start(cam->getEyePosition().x,cam->getEyePosition().y,cam->getEyePosition().z);
-        btVector3 end(start.x() + dir_cam.x,start.y() + dir_cam.y,start.z() + dir_cam.z);
-        btCollisionWorld::ClosestRayResultCallback RayCallback(start, end);
-        m_engine->getPhysics()->rayTest(start,end,RayCallback);
-
-        ImGui::Begin("Picker", &m_pickerEnabled);
-        if(RayCallback.hasHit())
-        {
-            btVector3 target = RayCallback.m_hitPointWorld;
-            ImGui::Text("Target coordinates : (%.3f,%.3f,%.3f)",target.x(),target.y(),target.z());
-
-        }
-        else
-        {
-            ImGui::Text("Nothing");
-        }
-        //        if(ImGui::Button("Teleport"))
-            //move player to target coordinate
-        ImGui::End();
-    }
+        m_pickerNode->update();
 }
 
 void GuiTools::togglePicker()
 {
     m_pickerEnabled = !m_pickerEnabled;
+    m_pickerNode->setVisible(m_pickerEnabled);
 }
diff --git a/src/guitools.h b/src/guitools.h
index 6629278..b2c8da6 100644
--- a/src/guitools.h
+++ b/src/guitools.h
@@ -1,14 +1,17 @@
 #ifndef GUITOOLS_H
 #define GUITOOLS_H
 
-class Engine;
+#include "scene/containernode.h"
 
-class GuiTools
+class Engine;
+class ScenePicker;
+
+class GuiTools : public ContainerNode
 {
-    Engine* m_engine;
+    ScenePicker* m_pickerNode;
     bool m_pickerEnabled;
 public:
-    GuiTools(Engine*);
+    GuiTools();
     void update();
     void togglePicker();
 };
diff --git a/src/scene/gibgeneratornode.cpp b/src/scene/gibgeneratornode.cpp
index 963fcb5..d965aa7 100644
--- a/src/scene/gibgeneratornode.cpp
+++ b/src/scene/gibgeneratornode.cpp
@@ -26,7 +26,6 @@ void GibGeneratorNode::createGib(GraphicalNode* graphicalPart,
 
         m_gibs.push_back(new Gib(body, graphicalPart, getEngine().getTime()+lifeSpan));
         addChild(graphicalPart);
-        m_scene->updateShaders(); // TODO : optimisations needed
     }
 }
 
diff --git a/src/scene/graphicalnode.cpp b/src/scene/graphicalnode.cpp
index 0902be1..a8f8960 100644
--- a/src/scene/graphicalnode.cpp
+++ b/src/scene/graphicalnode.cpp
@@ -3,7 +3,8 @@
 #include "glm/ext.hpp"
 #include <iostream>
 
-void GraphicalNode::setSceneTree(SceneTree *tree){
+void GraphicalNode::setSceneTree(SceneTree *tree)
+{
     if(isVisible())
     {
         if(m_scene != nullptr)
@@ -14,7 +15,8 @@ void GraphicalNode::setSceneTree(SceneTree *tree){
     m_scene = tree;
 }
 
-void GraphicalNode::resetTransform(){
+void GraphicalNode::resetTransform()
+{
     setTransform(glm::mat4());
 }
 
diff --git a/src/scene/gui/buttonnode.cpp b/src/scene/gui/buttonnode.cpp
index ca7d0f8..fc62010 100644
--- a/src/scene/gui/buttonnode.cpp
+++ b/src/scene/gui/buttonnode.cpp
@@ -43,7 +43,6 @@ void ButtonNode::update()
 
     if(m_label->wasUpdated()){
         m_label->setPosition(m_shape->getDimension()/glm::vec2(2,2) - m_label->getDimension()/glm::vec2(2,2));
-        getEngine().getScene()->updateShaders();
     }
 
     for (auto action : input->getActions())
diff --git a/src/scene/lightnode.cpp b/src/scene/lightnode.cpp
index d8748f7..c198a64 100644
--- a/src/scene/lightnode.cpp
+++ b/src/scene/lightnode.cpp
@@ -3,6 +3,13 @@
 #include <SparrowRenderer/light.h>
 #include <glm/mat3x3.hpp>
 
+void LightNode::setSceneTree(SceneTree *tree)
+{
+    GraphicalNode::setSceneTree(tree);
+    if(m_scene != nullptr)
+        m_scene->registerLightType(m_light->getFlags());
+}
+
 void LightNode::update()
 {
     if(m_transformChanged)
diff --git a/src/scene/lightnode.h b/src/scene/lightnode.h
index 8cb11a1..49d343a 100644
--- a/src/scene/lightnode.h
+++ b/src/scene/lightnode.h
@@ -11,6 +11,8 @@ class LightNode : public GraphicalNode
 public:
     LightNode(Light* light) : m_light(light) {}
 
+    virtual void setSceneTree(SceneTree* tree);
+
     virtual void update();
 
     virtual Light* getLight() { return m_light; }
diff --git a/src/scene/meshnode.cpp b/src/scene/meshnode.cpp
index 72b8c92..d0dca2a 100644
--- a/src/scene/meshnode.cpp
+++ b/src/scene/meshnode.cpp
@@ -6,6 +6,13 @@
 #include <btBulletCollisionCommon.h>
 #include <btBulletDynamicsCommon.h>
 
+void MeshNode::setSceneTree(SceneTree *tree)
+{
+    GraphicalNode::setSceneTree(tree);
+    if(m_scene != nullptr)
+        m_scene->registerMeshType(m_geometry.mesh->getFlags());
+}
+
 void MeshNode::setDepth(float depth){
     m_geometry.mesh->setDepth(depth);
 }
diff --git a/src/scene/meshnode.h b/src/scene/meshnode.h
index a214855..e1aeae6 100644
--- a/src/scene/meshnode.h
+++ b/src/scene/meshnode.h
@@ -26,6 +26,8 @@ public:
     // this behaviour allows the use of the same meshes in multiple nodes
     MeshNode(Mesh* mesh, bool visible = true) : GraphicalNode(visible), m_geometry(mesh, glm::mat4()), m_rigidBody(nullptr) {}
 
+    virtual void setSceneTree(SceneTree* tree);
+
     virtual void update();
 
     void setDepth(float depth);
diff --git a/src/scene/scenetree.cpp b/src/scene/scenetree.cpp
index e3df85c..6a6fc08 100644
--- a/src/scene/scenetree.cpp
+++ b/src/scene/scenetree.cpp
@@ -13,7 +13,8 @@
 SceneTree::SceneTree(const Engine &engine) :
     Scene(),
     m_engine(engine),
-    m_skybox(NULL)
+    m_shaderRefreshRequired(false),
+    m_camera(nullptr)
 {
     DeferredPipeline *pipeline = new DeferredPipeline();
     m_pipeline = pipeline;
@@ -28,9 +29,10 @@ SceneTree::~SceneTree()
 
 void SceneTree::setMainCamera(CameraNode *camNode)
 {
-    ((DeferredPipeline*)m_pipeline)->setCamera(camNode->getCamera());
+    m_camera = camNode->getCamera();
+    ((DeferredPipeline*)m_pipeline)->setCamera(m_camera);
     sf::Vector2u size = getEngine().getWindow()->getSize();
-    camNode->getCamera()->resize(size.x, size.y);
+    m_camera->resize(size.x, size.y);
 }
 
 SceneIterator<Light*>* SceneTree::getLights()
@@ -43,11 +45,37 @@ SceneIterator<GeometryNode*>* SceneTree::getGeometry()
     return new ArrayIterator<GeometryNode*>(m_geometries);
 }
 
+void SceneTree::getMeshTypes(std::vector<unsigned int> &meshTypes)
+{
+    for(unsigned int type : m_meshTypes)
+        meshTypes.push_back(type);
+}
+
+void SceneTree::getLightTypes(std::vector<unsigned int> &lightTypes)
+{
+    for(unsigned int type : m_lightTypes)
+        lightTypes.push_back(type);
+}
+
 void SceneTree::update()
 {
     m_root.update();
 }
 
+void SceneTree::registerMeshType(unsigned int meshType)
+{
+    auto ret = m_meshTypes.emplace(meshType);
+    if(ret.second)
+        m_shaderRefreshRequired = true;
+}
+
+void SceneTree::registerLightType(unsigned int lightType)
+{
+    auto ret = m_lightTypes.emplace(lightType);
+    if(ret.second)
+        m_shaderRefreshRequired = true;
+}
+
 void SceneTree::addToIndex(SceneNode* node){
     Light *light = node->getLight();
     GeometryNode *geometrynode = node->getGeometryNode();
@@ -80,5 +108,9 @@ void SceneTree::removeFromIndex(SceneNode *node){
 
 void SceneTree::updateShaders()
 {
-    ((DeferredPipeline*) m_pipeline)->refreshScene(this);
+    if(m_shaderRefreshRequired)
+    {
+        ((DeferredPipeline*) m_pipeline)->refreshScene(this);
+        m_shaderRefreshRequired = false;
+    }
 }
diff --git a/src/scene/scenetree.h b/src/scene/scenetree.h
index eb23d51..dede801 100644
--- a/src/scene/scenetree.h
+++ b/src/scene/scenetree.h
@@ -3,6 +3,7 @@
 
 #include <vector>
 #include <string>
+#include <unordered_set>
 #include "SparrowRenderer/scene.h"
 #include "containernode.h"
 #include "engine.h"
@@ -23,14 +24,17 @@ public:
     virtual SceneIterator<Light*>* getLights();
     virtual SceneIterator<GeometryNode*>* getGeometry();
 
+    virtual void getMeshTypes(std::vector<unsigned int> &meshTypes);
+    virtual void getLightTypes(std::vector<unsigned int> &lightTypes);
+
     void update();
 
-    Texture* getSkybox() {return m_skybox;}
-    void setSkybox(Texture* skybox) {m_skybox = skybox;}
-
     void setMainCamera(CameraNode *camNode);
+    Camera* getCamera() const { return m_camera; }
 
     ContainerNode* getRootObject(){return &m_root;}
+    void registerMeshType(unsigned int meshType);
+    void registerLightType(unsigned int lightType);
     void addToIndex(SceneNode* node);
     void removeFromIndex(SceneNode *node);
     void updateShaders();
@@ -47,7 +51,10 @@ private:
     ContainerNode m_root;
     std::vector<Light*> m_lights;
     std::vector<GeometryNode*> m_geometries;
-    Texture* m_skybox;
+    std::unordered_set<unsigned int> m_meshTypes;
+    std::unordered_set<unsigned int> m_lightTypes;
+    bool m_shaderRefreshRequired;
+    Camera* m_camera;
 };
 
 #endif // SCENETREE_H
diff --git a/src/sparrowshell/sparrowshell.cpp b/src/sparrowshell/sparrowshell.cpp
index 7f4477a..57970b9 100644
--- a/src/sparrowshell/sparrowshell.cpp
+++ b/src/sparrowshell/sparrowshell.cpp
@@ -147,7 +147,6 @@ void SparrowShell::toggleShell()
   //  for(auto child : m_children)
    //     child->toggleVisibility();
 //    m_buffer->toggleBuffer();
-    m_scene->updateShaders();
 }
 
 void SparrowShell::update()
diff --git a/src/test/main.cpp b/src/test/main.cpp
index 4020ad5..2b33b19 100644
--- a/src/test/main.cpp
+++ b/src/test/main.cpp
@@ -213,7 +213,6 @@ public:
         LightNode *sunLight = new LightNode(sun);
 
         scene->getRootObject()->addChild(ambientLight);
-        scene->getRootObject()->addChild(sunLight);
 
         if(m_config->scene == "sponza")
         {
@@ -248,6 +247,7 @@ public:
             sun->setShadowView(glm::vec3(80));
         }
 
+        scene->getRootObject()->addChild(sunLight);
     }
 
     std::string getScene(){return m_demo_scene;}
@@ -427,7 +427,6 @@ int main(){
 //    engine.getScene()->getRootObject()->addChild(bgrn);
 
     // preparing shaders and launching the engine
-    engine.getScene()->updateShaders();
     engine.start();
 
     // pathfinding tests
diff --git a/src/tools/scenepicker.cpp b/src/tools/scenepicker.cpp
new file mode 100644
index 0000000..db0ec70
--- /dev/null
+++ b/src/tools/scenepicker.cpp
@@ -0,0 +1,90 @@
+#include "scenepicker.h"
+
+#include "engine.h"
+#include "guitools.h"
+#include "scene/scenetree.h"
+#include "scene/playercharacternode.h"
+
+#include <SparrowRenderer/parametricmesh.h>
+#include <SparrowRenderer/pbrmaterial.h>
+#include <SparrowRenderer/camera.h>
+
+#include <imgui/imgui.h>
+
+#include <btBulletCollisionCommon.h>
+#include <btBulletDynamicsCommon.h>
+#include <BulletDynamics/Character/btKinematicCharacterController.h>
+
+Mesh* ScenePicker::generateMesh()
+{
+    SphereGenerator generator;
+    PBRMaterial* mat = new PBRMaterial();
+    mat->albedo = glm::vec3(1, 0, 0); // red
+    mat->emission = glm::vec3(0.3, 0, 0); // emits some red
+    mat->metallic = 0.6f;
+    mat->roughness = 0.3f; // quite shiny
+    Mesh* m = generator.generateGeodesicMesh(mat, 2, 0.3f);
+    m->computeNormals();
+    m->setName("scenePicker");
+    m->initGL();
+    return m;
+}
+
+ScenePicker::ScenePicker() :
+    MeshNode(generateMesh()),
+    m_pickSucceeded(false)
+{
+}
+
+ScenePicker::~ScenePicker()
+{
+    delete m_geometry.mesh->getMaterial();
+    delete m_geometry.mesh;
+}
+
+void ScenePicker::update()
+{
+    pick();
+
+    bool isEnabled = true;
+    ImGui::Begin("Picker", &isEnabled);
+    if(m_pickSucceeded)
+    {
+        ImGui::Text("Intersection : ( %.3f, %.3f, %.3f )", m_pickedPos.x, m_pickedPos.y, m_pickedPos.z);
+    }
+    else
+    {
+        ImGui::Text("No intesection");
+    }
+    //        if(ImGui::Button("Teleport"))
+        //move player to target coordinate
+    ImGui::End();
+
+    if(!isEnabled)
+        getEngine().getGuiTools()->togglePicker();
+}
+
+void ScenePicker::pick()
+{
+    FirstPersonCamera* cam = dynamic_cast<FirstPersonCamera*>(getEngine().getScene()->getCamera());
+    if(cam != nullptr)
+    {
+        glm::vec3 dir_cam = cam->getDirection()*100;
+        btVector3 start(cam->getEyePosition().x, cam->getEyePosition().y, cam->getEyePosition().z);
+        btVector3 end = start;
+        end += btVector3(start.x() + dir_cam.x, start.y() + dir_cam.y, start.z() + dir_cam.z);
+        btCollisionWorld::ClosestRayResultCallback RayCallback(start, end);
+        getEngine().getPhysics()->rayTest(start,end,RayCallback);
+
+        m_pickSucceeded = RayCallback.hasHit();
+        if(m_pickSucceeded)
+        {
+            btVector3 target = RayCallback.m_hitPointWorld;
+            m_pickedPos = glm::vec3(target.x(), target.y(), target.z());
+            m_geometry.modelMatrix = glm::translate(glm::mat4(), m_pickedPos);
+        }
+    }
+    else
+        m_pickSucceeded = false;
+}
+
diff --git a/src/tools/scenepicker.h b/src/tools/scenepicker.h
new file mode 100644
index 0000000..41ab04d
--- /dev/null
+++ b/src/tools/scenepicker.h
@@ -0,0 +1,26 @@
+#ifndef SCENEPICKER_H
+#define SCENEPICKER_H
+
+#include "scene/meshnode.h"
+
+class ScenePicker : public MeshNode
+{
+    static Mesh* generateMesh();
+
+    glm::vec3 m_pickedPos;
+    bool m_pickSucceeded;
+
+public:
+    ScenePicker();
+
+    virtual ~ScenePicker();
+
+    virtual void update();
+
+    void pick();
+
+    glm::vec3 getIntersection() { return m_pickedPos; }
+    bool getTraceSucceeded() { m_pickSucceeded; }
+};
+
+#endif // SCENEPICKER_H