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 #include <GL/glut.h>
 #include <stdlib.h>
 #include <math.h>
 #include <iostream>
 #include <fstream>
 using namespace std;
 
 //fstream output("data.txt",ios::out);
 
 double dt = 0.05; // this is the time step
 float coeF = 0.5;
 float verysmall = 0.001;
-    glPushMatrix();
+float totaltime = 0.0;
 float gravity = 0.1;
 GLfloat near = 0.1,far = 20.0;
 GLfloat startdispz = -1.0;
 
 const float DEG2RAD = 3.14159/180;
 
 class ball
 {
 	private:
 		// ax acceleration in x, px position in x, vx velocity in x
 		double ax,ay,az,px,py,pz,vx,vy,vz,size;
 
 	public:
 		ball()
 		{
 			px=0.0;py=0.0;
 		}
 		ball(double dummyvx, double dummyvy,double dummyvz)
 		{
 			px=0;	py=0.1;	pz=0;	size=0.1;
 			vx=dummyvx;	vy=dummyvy;	vz=dummyvz;	ay=gravity;
 		}
 		double getpx(){return px;}  double getpy(){return py;}	double getpz(){return pz;}
 		double getvx(){return vx;}  double getvy(){return vy;}	double getvz(){return vz;}
 		double getballsize(){return size;}
 
 		double getspeed(){return  sqrt(py*py + px*px + pz*pz);}
 
 		void evolve()
 		{
 			//cout << "vy" << vy << "\n";
 			vy += (-gravity*dt);							// equation for the y component of v
 			px += vx*dt;	py += vy*dt;	pz += vz*dt;	// equations for all 3 components of p
 			totaltime += dt;								// update total time
 			//output << totaltime << " " << px << " "   << py << " "  << pz << "\n";
 			//cout << totaltime << " " << py  << " " << pz << "\n";
 			//terminate when we hit the ground i.e pz < 0
 
 			if(py < size)
 			{
 				py = size;
 				vy = -vy*coeF;
 
 				//cout << "The ball has hit the ground\n";
 				//vx=0;	vy=0;	vz=0;
 				//output.close();
 				//exit(0);
 			}
 		}
 };
 
 // ball start at origin with velocity vector as in the constructor
 ball golfball(0.0, 0.4, 0.8);
 
 void init(void)
 {
 	glClearColor(1.0,1.0,1.0,0.0);
 }
 
 void drawCircle(float Radius, int numPoints)
 {
 	glBegin( GL_LINE_LOOP );
 	for( int i=0; i<numPoints; i++ )
 	{
 		float Angle = i * (2.0*M_PI/numPoints);
 		float X = cos( Angle )*Radius;
 		float Y = sin( Angle )*Radius;
 		glVertex2f( X, Y );
 	}
 	glEnd();
 }
 
 void display(void)
 {
 	glMatrixMode(GL_PROJECTION);
 	glLoadIdentity();
 	gluPerspective(40,1,near,far);
 
 	glMatrixMode(GL_MODELVIEW);
 	glLoadIdentity();
 	gluLookAt(0.0, 2.0, -3.0, 0.0, 0.0, 10.0, 0.0, 1.0, 0.0);
 
 	glClear(GL_COLOR_BUFFER_BIT);
 
 	glPushMatrix();
 		glColor3f (0.0, 0.0, 0.0);
 		glTranslatef(golfball.getpx(),golfball.getpy(),startdispz - golfball.getpz());
 		glutSolidSphere(golfball.getballsize(),20,20);
 	glPopMatrix();
 
 	glPushMatrix();
 		glColor3f (0.0, 1.0, 0.0);
 		glTranslatef(0,0.0,-7.5);
 		glRotatef(90, 1.0, 0.0, 0.0);
 		drawCircle(0.1,24);
 		glRotatef(-90, 1.0, 0.0, 0.0);
 	glPopMatrix();
 
 	glFlush();
 	glutSwapBuffers();
 }
 
 void keyboard(unsigned char key, int x, int y)
 {
 	switch (key)
 	{
 		case 'q':
 		exit(0);
 	}
 }
 
 void evolve(int a)
 {
     // evolve system here
 	golfball.evolve();
 	glutPostRedisplay();
 	glutTimerFunc(20,evolve,20);
 }
 
 int main(int argc, char** argv)
 {
    glutInit(&argc, argv);
    glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize (800, 800);
    glutCreateWindow (argv[0]);   init();
    glutKeyboardFunc (keyboard);
    //  glutIdleFunc(evolve);
    glutTimerFunc(100,evolve,100);
    glutDisplayFunc (display);
    cout << "Hello All on CG6301\n";
    cout << "This program models projectile motion, the golf ball moves under gravity(no friction)\n";
    cout << "The file is closed and the program terminates when the ball is deemed to have hit the ground \n";
    cout << "The lab questions ask you to determine how accurately we have modelled the system\n";
 
    glutMainLoop();
    return 0;
 }