#include <GLUT/glut.h>
#include <iostream>
using namespace std;
 
//initialising variables
float x_positie = 0.0, x_doel = 0.0, x_doel2, x_kracht = 0.02, x_versnelling = -0.001, weerstand = 0.99, doeldist = 0.0;
float y_positie = 0.0, y_doel = 0.0, y_doel2, y_kracht = 0.02, y_versnelling = -0.001, rot = 0.0;
float z_positie = 0.0, z_doel = 0.0, z_doel2, z_kracht = 0.02, z_versnelling = -0.001, t = 0.0;
//initialising states 
void init()
{
	glClearColor(0.0,0.0,0.0,1.0);
	glEnable(GL_BLEND);
	glBlendFunc(GL_ONE, GL_ONE);
}
 
//reshaping the viewport and projection
void reshape(int width, int height)
{
	glViewport(0, 0, 1024, 768);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(60.,(GLfloat) width/(GLfloat) height,0.1, 800.0);
	glMatrixMode(GL_MODELVIEW);
	gluLookAt(0.0,0.0,200.0, 0.0, 0.0, 0.0, 0,1,0);
 
}
 
//reading the keyboard input
void key(unsigned char key, int x, int y){
	switch (key){
		case 32:
		x_doel2 = (rand()%160-80);
		y_doel2 = (rand()%160-80);
		z_doel2 = (rand()%160-80);
		doeldist = sqrt (pow((x_doel-x_doel2),2.0) + pow((y_doel-y_doel2),2.0) + pow((z_doel-z_doel2),2.0));
		break;
		}
}
 
//drawing and displaying 
void display()
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
		//glRotatef(0.5,0,1,0);
 
		glPushMatrix();
			x_positie += x_kracht ; 
			y_positie += y_kracht ;
			z_positie += z_kracht ;
			x_versnelling = (x_doel2 - x_positie)*0.0003;
			y_versnelling = (y_doel2 - y_positie)*0.0003;
			z_versnelling = (z_doel2 - z_positie)*0.0003;
			x_kracht += x_versnelling;
			y_kracht += y_versnelling;
			z_kracht += z_versnelling;
			x_kracht *= weerstand;
			y_kracht *= weerstand;
			z_kracht *= weerstand;
 
			glBegin(GL_LINES);
				glVertex3f(x_doel,y_doel,z_doel);
				glVertex3f(x_positie,y_positie,z_positie);
			glEnd();
 
			glTranslatef(x_positie, y_positie, z_positie);
			glColor4f(0.6, 0.0, 0.0, 1.0);
			glutSolidSphere(2.0,9,9);
		glPopMatrix();
 
		glPushMatrix();
		glTranslatef(x_positie+sin(t)*9,y_positie+cos(t)*9,z_positie);
		glutSolidSphere(2.0,9,9);
		        if (t > 6.2829){
			    t = 0;
			}
		t += 0.02;
		glPopMatrix();
 
		glPushMatrix();
		        glTranslatef(x_doel, y_doel, z_doel);
		        glColor4f(0.3,0.3,0.3,0.3);
		        glutSolidSphere(5.0,15,15);
		glPopMatrix();
		glutSwapBuffers();
}
 
//main loop with initialising of window and glut, assigning functions
int main(int argc, char** argv)
{
	srand(time(NULL));
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
	glutGameModeString("1024x768:32");
	glutEnterGameMode();
	init();
	glutDisplayFunc(display);
	glutIdleFunc(display);
	glutReshapeFunc(reshape);
	glutKeyboardFunc(key);
	glutMainLoop();
	return 0;	
}