//http://www.timestocome.com

//linda cobb

//fall 99

//plot routine for physics data





//open a display window

//and plot data from coffee cooling problem



#include <stdlib.h>

#include <stdio.h>

#include <math.h>

#include <GLUT/glut.h>





#define TIMESTEP  0.001

#define XMIN     - 0.5

#define YMIN      70.0

#define XMAX      1.0

#define YMAX      95.0



void display (void){

  

  double i,j;

  double Ts = 20;           //room temperature

  double Told = 90.0;       //begining temperature of coffee

  double t =0.0;            // begining time

  double r=0.27;            //estimated cooling constant

  double Tnew = 90.0;       //new temperature

  typedef GLfloat point2[2];//define a point array

  double h = TIMESTEP;      //size of increment

  int temp;





  //plot black coffee in red	

  point2 p = {0.0, Tnew};                   //start somewhere

  glClear(GL_COLOR_BUFFER_BIT);             //clear window

 

  glColor3f(1.0, 0.0, 0.0);

	while(Tnew >= 80){

	  if(t<TIMESTEP){

	    Tnew = Told;

	  }else{

	    Tnew = Told - h*r*Told;

	  }

	  t += TIMESTEP;

	  Told = Tnew;

	  

	  p[0] = t;	              //time

	  p[1] = Tnew;	              //temp

	 //plot points

		glBegin(GL_POINTS);

		glVertex2fv(p);

		glEnd();

	}

	

	for(i=0; i<5; i+=0.1){          //add cream now

	p[0] = t;

	p[1] = Tnew-i;

	glBegin(GL_POINTS);

	glVertex2fv(p);

        glEnd();

	}





  //plot coffee w/ cream in green

  glColor3f(0.0, 1.0, 0.0);

  r = 0.25;                    //new cooling constant

  Told = 90 - 5.0;             //coffee temp adjusted for cream

  Tnew = Told;                 //set begining variable

  t = 0.0;                     //restart timer



  while(Tnew >= 75){

    if(t<TIMESTEP){

      Tnew = Told;

    }else{

      Tnew = Told -h*r*Told;

    }

    t += TIMESTEP;

    Told = Tnew;

    p[0] = t;

    p[1] = Tnew;

    //plot points

           glBegin(GL_POINTS);

	   glVertex2fv(p);

	   glEnd();



  }



  Told = 85;

  Tnew = Told;

  t = 0.0;

  r = 0.25; 



 

  //draw axis in black 

  //verticle line at x = 0

  glColor3f( 0.0, 0.0, 0.0);

    for(j = 70.0; j < 100; j+=0.01){

    p[0]= 0.0;

    p[1]= j;

    glBegin(GL_POINTS);

    glVertex2fv(p);

    glEnd();

  }  

 

  //horizontal line at y = 75'C

  glColor3f(0.0, 0.0, 0.0);

    for(j = 0.0; j <100.00; j+= 0.001){

     p[0]=j;

     p[1]=75;

     glBegin(GL_POINTS);

     glVertex2fv(p);

     glEnd();

    }



}



 void myinit (void){

//attributes

	glClearColor(1.0, 1.0, 1.0, 0.0);	//backround



//set up viewing

	glMatrixMode(GL_PROJECTION);

       	gluOrtho2D(XMIN, XMAX, YMIN, YMAX);	//size of x and y axis

//2d coordinate sys lower left corner 0,0

	glMatrixMode(GL_MODELVIEW);

 }





void main(int argc, char **argv)

{

    glutInit(&argc, argv);

    glutInitWindowSize(500, 250);

    glutInitDisplayMode(GLUT_RGB|GLUT_SINGLE);

    (void)glutCreateWindow("coffee cooling");

    glutDisplayFunc(display);

    myinit();

    glutMainLoop();



}