diff --git a/include/eepp/math/interpolation1d.hpp b/include/eepp/math/interpolation1d.hpp
index 6383da740..e7978c9e4 100644
--- a/include/eepp/math/interpolation1d.hpp
+++ b/include/eepp/math/interpolation1d.hpp
@@ -47,7 +47,10 @@ class EE_API Interpolation1d {
 		Interpolation1d& waitAndAdd( const Float& pos, const Time& waitTime, const Time& addTime );
 
 		/** Start the animation */
-		Interpolation1d& start( OnPathEndCallback PathEndCallback = OnPathEndCallback(), OnStepCallback StepCallback = OnStepCallback() );
+		Interpolation1d& start();
+
+		/** Start the animation */
+		Interpolation1d& start( OnPathEndCallback PathEndCallback, OnStepCallback StepCallback = OnStepCallback() );
 
 		/** Stop the animation */
 		Interpolation1d& stop();
diff --git a/include/eepp/math/interpolation2d.hpp b/include/eepp/math/interpolation2d.hpp
index f3fe7f9ac..ac9465a43 100755
--- a/include/eepp/math/interpolation2d.hpp
+++ b/include/eepp/math/interpolation2d.hpp
@@ -47,11 +47,14 @@ class EE_API Interpolation2d {
 		/** Same as add( pos, waitTime ).add( pos, addTime ); */
 		Interpolation2d& waitAndAdd( const Vector2f& pos, const Time& waitTime, const Time& addTime );
 
+		/** Start the animation ( will reset the current state, and start from the beginning ) */
+		Interpolation2d& start();
+
 		/** Start the animation ( will reset the current state, and start from the beginning )
 		*	@param PathEndCallback An optional callback fired when the animation ends.
 		*	@param StepCallback An optional callback that is fired every time that a step is completed.
 		*/
-		Interpolation2d& start( OnPathEndCallback PathEndCallback = OnPathEndCallback(), OnStepCallback StepCallback = OnStepCallback() );
+		Interpolation2d& start( OnPathEndCallback PathEndCallback, OnStepCallback StepCallback = OnStepCallback() );
 
 		/** Stop the animation ( Enable = false ) */
 		Interpolation2d& stop();
diff --git a/src/eepp/math/interpolation1d.cpp b/src/eepp/math/interpolation1d.cpp
index 31d8d6f5e..04987dee1 100644
--- a/src/eepp/math/interpolation1d.cpp
+++ b/src/eepp/math/interpolation1d.cpp
@@ -18,19 +18,16 @@ Interpolation1d::Interpolation1d() :
 	mSpeed(1.3f),
 	mActP(NULL),
 	mNexP(NULL),
-	mOnPathEndCallback(NULL),
-	mOnStepCallback(NULL)
+	mOnPathEndCallback(),
+	mOnStepCallback()
 {
 }
 
 Interpolation1d::~Interpolation1d() {
 }
 
-Interpolation1d& Interpolation1d::start( OnPathEndCallback PathEndCallback, OnStepCallback StepCallback) {
+Interpolation1d& Interpolation1d::start() {
 	mEnable				= true;
-	mOnPathEndCallback	= PathEndCallback;
-	mOnStepCallback		= StepCallback;
-
 	if ( mPoints.size() ) {
 		mActP = &mPoints[ 0 ];
 
@@ -45,6 +42,13 @@ Interpolation1d& Interpolation1d::start( OnPathEndCallback PathEndCallback, OnSt
 	return *this;
 }
 
+Interpolation1d& Interpolation1d::start( OnPathEndCallback PathEndCallback, OnStepCallback StepCallback) {
+	start();
+	mOnPathEndCallback	= PathEndCallback;
+	mOnStepCallback		= StepCallback;
+	return *this;
+}
+
 Interpolation1d& Interpolation1d::stop() {
 	mEnable	= false;
 	return *this;
@@ -79,8 +83,8 @@ Interpolation1d & Interpolation1d::reset() {
 	mUpdate	= true;
 	mEnded = false;
 	mCurTime = Time::Zero;
-	mOnPathEndCallback = NULL;
-	mOnStepCallback = NULL;
+	mOnPathEndCallback = OnPathEndCallback();
+	mOnStepCallback = OnStepCallback();
 
 	if ( mPoints.size() )
 		mCurPos = mPoints[0].p;
diff --git a/src/eepp/math/interpolation2d.cpp b/src/eepp/math/interpolation2d.cpp
index 53ee8e004..9cf3e9584 100755
--- a/src/eepp/math/interpolation2d.cpp
+++ b/src/eepp/math/interpolation2d.cpp
@@ -15,18 +15,16 @@ Interpolation2d::Interpolation2d() :
 	mCurPoint(0),
 	mCurTime(Time::Zero),
 	mSpeed(1.3f),
-	mOnPathEndCallback(NULL),
-	mOnStepCallback(NULL)
+	mOnPathEndCallback(),
+	mOnStepCallback()
 {
 }
 
 Interpolation2d::~Interpolation2d() {
 }
 
-Interpolation2d& Interpolation2d::start( OnPathEndCallback PathEndCallback, OnStepCallback StepCallback ) {
+Interpolation2d& Interpolation2d::start() {
 	mEnable				= true;
-	mOnPathEndCallback	= PathEndCallback;
-	mOnStepCallback		= StepCallback;
 
 	if ( mPoints.size() ) {
 		mActP = &mPoints[ 0 ];
@@ -42,6 +40,13 @@ Interpolation2d& Interpolation2d::start( OnPathEndCallback PathEndCallback, OnSt
 	return *this;
 }
 
+Interpolation2d& Interpolation2d::start( OnPathEndCallback PathEndCallback, OnStepCallback StepCallback ) {
+	start();
+	mOnPathEndCallback	= PathEndCallback;
+	mOnStepCallback		= StepCallback;
+	return *this;
+}
+
 Interpolation2d& Interpolation2d::stop() {
 	mEnable = false;
 	return *this;
@@ -65,8 +70,8 @@ Interpolation2d& Interpolation2d::reset() {
 	mCurTime = Time::Zero;
 	mUpdate = true;
 	mEnded = false;
-	mOnPathEndCallback = NULL;
-	mOnStepCallback = NULL;
+	mOnPathEndCallback = OnPathEndCallback();
+	mOnStepCallback = OnStepCallback();
 
 	if ( mPoints.size() )
 		mCurPos = mPoints[0].p;