//++++++++++++++++++++++++++++++++source for Pacific.h


// this class loads and stores a specific vector field data set
// NPacific.txt
class Pacific
{
	public:
	Pacific();

	void getVec(float X,float Y, float &dx, float &dy);
	// input a vector defined on [0..1][0..1]. 
	// output a velocity vector.

	private:

	int rows,cols;

	float **xv;
	float **yv;
};


//++++++++++++++++++++++++++++++++++++++++++++++++++

//+++++++++++++++++++++++++++++++++source for Pacific.cpp

#include <GL/glut.h>
#include <stdio.h>
#include <iostream.h>

#include "Pacific.h"


Pacific::Pacific()
{
	FILE *fp;

	int r,c,i,j;

	fp = fopen("NPacific.txt","r");

	fscanf(fp,"%d %d",&r,&c);

	cerr << "ROWS COLS " << r << " " << c << "\n";

	rows = r;
	cols = c;

	xv = new float*[rows];
	yv = new float*[rows];

	for(i=0;i<rows;++i)
	{

		xv[i] = new float[cols];
		yv[i] = new float[cols];
	}

	for(i=0;i<rows;++i)
	{
		for(j=0;j<cols;++j)
		{
			fscanf(fp,"%f %f",&xv[i][j],&yv[i][j]);
		}
	}

}

void Pacific::getVec(float X,float Y, float &dx, float &dy)
{
	// remaps x,y values into the grid
	// does bi-linear interpolation

	float xx,yy;
	int ix,iy;
	float px,py;
	float dx1,dx2,dy1,dy2;

	xx = X*(cols-1.2);
	yy = Y*(rows-1.2);

	ix = xx; 
	iy = yy;

	px = xx - ix;
	py = yy - iy;

	dx1 = (xv[iy][ix]*(1.0-px) + xv[iy][ix+1]*px)*0.1;
	dy1 = (yv[iy][ix]*(1.0-px) + yv[iy][ix+1]*px)*0.1;

	dx2 = (xv[iy+1][ix]*(1.0-px) + xv[iy+1][ix+1]*px)*0.1;
	dy2 = (yv[iy+1][ix]*(1.0-px) + yv[iy+1][ix+1]*px)*0.1;
	
	dx = dx1*(1.0-py) + dx2*py;
	dy = dy1*(1.0-py) + dy2*py;
}