varying vec4 lastPosition;   //Fragment position in the last frame
varying vec4 currentPosition;//Fragment position in the current frame

uniform sampler2D SaliencyMap; //Saliency map: Edge detector (only magnitude) + center surround differences

uniform float time; //Frame time.
uniform float habituation; //Habituation time for pixel's object

//Constants for normalizing the optical fow map
uniform float m;  //0.4
uniform float Am; //700 pixels/s

//Constants for normalizing the habituation
uniform float h;  //5
uniform float Ah; //12.5s

//Viewport size
uniform vec2 size;

void main()
{		
	vec2 coordCurrent = (currentPosition.xy/currentPosition.w +1) /2.;
	vec2 coordLast =  (lastPosition.xy   /lastPosition.w   + 1 ) /2.;
	vec2 distance = abs(coordCurrent * size - coordLast * size);
		
	//////////////////////////////////////////////////////////////////////////////////////////
	//MOTION SALIENCY
	float speed = sqrt(dot(distance,distance))/time; //Mod
	float left = 1. / ( m * sqrt(2.*3.141566));
	float right = - ((speed/Am)*(speed/Am)) / (m*m);
	float motionSaliency = 1.-left*exp(right); 
		
	//////////////////////////////////////////////////////////////////////////////////////////
	//SCENE SALIENCY
	float sceneSaliency = texture2D(SaliencyMap,coordCurrent).r;

	//////////////////////////////////////////////////////////////////////////////////////////
	//HABITUATION SALIENCY
	left = 1. / ( h * sqrt(2.*3.141566));
	right = -(habituation*habituation)/(h*h);
	float habituationSaliency = left*exp(right)*Ah; 
	
	//////////////////////////////////////////////////////////////////////////////////////////

	float saliency = motionSaliency * (sceneSaliency * 0.8 + habituationSaliency * 0.2);

	gl_FragColor = saliency;
}