diff --git a/sources/reactphysics3d/engine/PhysicsEngine.cpp b/sources/reactphysics3d/engine/PhysicsEngine.cpp
index 5465a817..4b9d84c8 100644
--- a/sources/reactphysics3d/engine/PhysicsEngine.cpp
+++ b/sources/reactphysics3d/engine/PhysicsEngine.cpp
@@ -19,6 +19,7 @@
 
 // Libraries
 #include "PhysicsEngine.h"
+#include "../integration/SemiImplicitEuler.h"
 
 // We want to use the ReactPhysics3D namespace
 using namespace reactphysics3d;
@@ -31,15 +32,118 @@ PhysicsEngine::PhysicsEngine(PhysicsWorld* world, const Time& timeStep) throw (s
         // Throw an exception
         throw std::invalid_argument("Exception in PhysicsEngine constructor : World pointer cannot be NULL");
     }
-}
-
-// Copy-constructor
-PhysicsEngine::PhysicsEngine(const PhysicsEngine& engine)
-              :world(engine.world), timer(engine.timer) {
 
+    // Creation of the Semi-Implicit Euler integration algorithm
+    integrationAlgorithm = new SemiImplicitEuler();
 }
 
 // Destructor
 PhysicsEngine::~PhysicsEngine() {
-
+    delete integrationAlgorithm;
+}
+
+void PhysicsEngine::update() {
+    updateCollision();
+}
+
+// TODO : Delete this method
+// Update the physics simulation
+void PhysicsEngine::updateDynamic() {
+    // Check if the physics simulation is running
+    if (timer.getIsRunning()) {
+        // While the time accumulator is not empty
+        while(timer.getAccumulator() >= timer.getTimeStep().getValue()) {
+            // For each body in the dynamic world
+            for(std::vector<Body*>::const_iterator it = world->getBodyListStartIterator(); it != world->getBodyListEndIterator(); ++it) {
+                // If the body is a RigidBody and if the rigid body motion is enabled
+                RigidBody* rigidBody = dynamic_cast<RigidBody*>(*it);
+                if (rigidBody && rigidBody->getIsMotionEnabled()) {
+                    // Update the state of the rigid body
+                    updateBodyState(rigidBody, timer.getTimeStep());
+                }
+            }
+
+            // Update the timer
+            timer.update();
+        }
+
+        // For each body in the dynamic world
+        for(std::vector<Body*>::const_iterator it = world->getBodyListStartIterator(); it != world->getBodyListEndIterator(); ++it) {
+            // If the body is a RigidBody and if the rigid body motion is enabled
+            RigidBody* rigidBody = dynamic_cast<RigidBody*>(*it);
+            if (rigidBody && rigidBody->getIsMotionEnabled()) {
+                // Update the interpolation factor of the rigid body
+                // This one will be used to compute the interpolated state
+                rigidBody->setInterpolationFactor(timer.getInterpolationFactor());
+            }
+        }
+    }
+}
+
+// TODO : Delethe this method
+// Update the physics simulation
+void PhysicsEngine::updateCollision() {
+
+    // While the time accumulator is not empty
+    while(timer.getAccumulator() >= timer.getTimeStep().getValue()) {
+
+        // Remove all old collision contact constraints
+        world->removeAllContactConstraints();
+
+        // Compute the collision detection
+        if (collisionDetection.computeCollisionDetection(world)) {
+
+            // TODO : Delete this ----------------------------------------------------------
+            for (std::vector<Constraint*>::const_iterator it = world->getConstraintListStartIterator(); it != world->getConstraintListEndIterator(); ++it) {
+                RigidBody* rigidBody1 = dynamic_cast<RigidBody*>((*it)->getBody1());
+                RigidBody* rigidBody2 = dynamic_cast<RigidBody*>((*it)->getBody2());
+                rigidBody1->setIsMotionEnabled(false);
+                rigidBody2->setIsMotionEnabled(false);
+            }
+            // -----------------------------------------------------------------------------
+        }
+
+        // For each body in the dynamic world
+        for(std::vector<Body*>::const_iterator it = world->getBodyListStartIterator(); it != world->getBodyListEndIterator(); ++it) {
+            // If the body is a RigidBody and if the rigid body motion is enabled
+            RigidBody* rigidBody = dynamic_cast<RigidBody*>(*it);
+            if (rigidBody && rigidBody->getIsMotionEnabled()) {
+                // Update the state of the rigid body with an entire time step
+                updateBodyState(rigidBody, timer.getTimeStep());
+            }
+        }
+
+        // Update the timer
+        timer.update();
+    }
+
+    // For each body in the the dynamic world
+    for(std::vector<Body*>::const_iterator it = world->getBodyListStartIterator(); it != world->getBodyListEndIterator(); ++it) {
+        // If the body is a RigidBody and if the rigid body motion is enabled
+        RigidBody* rigidBody = dynamic_cast<RigidBody*>(*it);
+        if (rigidBody && rigidBody->getIsMotionEnabled()) {
+            // Update the interpolation factor of the rigid body
+            // This one will be used to compute the interpolated state
+            rigidBody->setInterpolationFactor(timer.getInterpolationFactor());
+        }
+    }
+}
+
+// Update the state of a rigid body
+void PhysicsEngine::updateBodyState(RigidBody* const rigidBody, const Time& timeStep) {
+
+    // If the gravity force is on
+    if(world->getIsGravityOn()) {
+        // Apply the current gravity force to the body
+        rigidBody->getCurrentBodyState().setForce(world->getGravity());
+    }
+
+    // The current body state of the body becomes the previous body state
+    rigidBody->updatePreviousBodyState();
+
+    // Integrate the current body state at time t to get the next state at time t + dt
+    integrationAlgorithm->integrate(rigidBody->getCurrentBodyState(), timer.getTime(), timeStep);
+
+    // If the body state has changed, we have to update some informations in the rigid body
+    rigidBody->update();
 }
diff --git a/sources/reactphysics3d/engine/PhysicsEngine.h b/sources/reactphysics3d/engine/PhysicsEngine.h
index 550b969f..59ca4836 100644
--- a/sources/reactphysics3d/engine/PhysicsEngine.h
+++ b/sources/reactphysics3d/engine/PhysicsEngine.h
@@ -22,6 +22,9 @@
 
 // Libraries
 #include "PhysicsWorld.h"
+#include "../integration/IntegrationAlgorithm.h"
+#include "../collision/CollisionDetection.h"
+#include "../body/RigidBody.h"
 #include "Timer.h"
 
 // Namespace ReactPhysics3D
@@ -29,23 +32,29 @@ namespace reactphysics3d {
 
 /*  -------------------------------------------------------------------
     Class PhysicsEngine :
-        This is an abstract class that represents the physics engine
+        This class represents the physics engine
         of the library.
     -------------------------------------------------------------------
 */
 class PhysicsEngine {
     protected :
-        PhysicsWorld* world;                    // Pointer to the physics world of the physics engine
-        Timer timer;                            // Timer of the physics engine
+        PhysicsWorld* world;                            // Pointer to the physics world of the physics engine
+        Timer timer;                                    // Timer of the physics engine
+        IntegrationAlgorithm* integrationAlgorithm;     // Integration algorithm used to solve differential equations of movement
+        CollisionDetection collisionDetection;          // Collision detection
+
+        void updateBodyState(RigidBody* const rigidBody, const Time& timeStep);           // Update the state of a rigid body
 
     public :
         PhysicsEngine(PhysicsWorld* world, const Time& timeStep) throw (std::invalid_argument);     // Constructor
         PhysicsEngine(const PhysicsEngine& engine);                                                 // Copy-constructor
-        virtual ~PhysicsEngine();                                                                   // Destructor
+        ~PhysicsEngine();                                                                           // Destructor
 
-        virtual void start();                                   // Start the physics simulation
-        virtual void stop();                                    // Stop the physics simulation
-        virtual void update()=0;                                // Update the physics simulation
+        void start();                                           // Start the physics simulation
+        void stop();                                            // Stop the physics simulation
+        void update();                                          // Update the physics simulation
+        void updateDynamic();                                   // TODO : Delete this method
+        void updateCollision();                                 // TODO : Delete this collision
         void initializeDisplayTime(const Time& displayTime);    // Initialize the display time
         void updateDisplayTime(const Time& newDisplayTime);     // Update the display time
 };