/* Huang-Jung Chang
   13207260
   Final Project on Virtual Location
   Please see paper for details
*/

#include <stdio.h>
#include <math.h>

#define R 0.5
#define FREQDIF 700.0


float ampgain(float x, float y, float xs, float ys);
float speakerdis(float r);


// calculating the amplitude gains for each speaker
// a = 1 - sqr(d)
float ampgain ( float x, float y, float xs, float ys)
{
	float xi, yi, a;
	
	xi = x - xs;
	yi = y - ys;
	a = 1 - (yi * yi + xi * xi);
	return a;
}


// speaker distance for the origin
float speakerdis(float r)
{
	return (r/sqrt(2.0));
}


void main()
{
	float x, y;
	float a1, a2, a3, a4, alla;
	float dis, ndis;
	float freq;
	float rx, ry;
	double q;
	
	printf("please enter x coordinate value of sound source: ");
	scanf("%f", &x);
	printf("please enter y coordinate value of sound source: ");
	scanf("%f", &y);
	printf("please enter frequency value of sound source: ");
	scanf("%f", &freq);
	dis = speakerdis(R);
	ndis = 0 - dis;					// negative value according to coordinate
	a1 = ampgain(x, y, ndis, dis);	// amplitudes for each speakers
	a2 = ampgain(x, y, dis, dis);
	a3 = ampgain(x, y, dis, ndis);
	a4 = ampgain(x, y, ndis, ndis);
	printf("the gain of speaker 1 is %f\n", a1);
	printf("the gain of speaker 2 is %f\n", a2);
	printf("the gain of speaker 3 is %f\n", a3);
	printf("the gain of speaker 4 is %f\n", a4);
	if ( freq > FREQDIF)
	{
		a1 = a1 * a1;
		a2 = a2 * a2;
		a3 = a3 * a3;
		a4 = a4 * a4;
	}
	alla = a1+a2+a3+a4;
	rx = (a1*ndis + a2*dis + a3*dis + a4*ndis) / alla;
	ry = (a1*dis + a2*dis + a3*ndis + a4*ndis) / alla;
	q = atan(ry/rx);
	if (freq <= FREQDIF)
	{
		printf("the velocity vector of the virtual sound source is (%f, %f) \n", rx, ry);
		printf("the velocity theta angle is %f in radian\n", q);
	}
	else
	{
		printf("the energy vector of the virtual sound source is (%f, %f) \n", rx, ry);
		printf("the energy theta angle is %f in radian\n", q);
	}
}