/*
	Simple Solar system 
	An example of attenuation. 
	The light is in the position of viewer
	(C) Bedrich Benes 2003
*/

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


#define K 0.01

GLfloat c=1,l,q;


void Init(void) 
{
  GLfloat light_position[] = {0, 0, 1, 1.0};
  GLfloat specular[] = {1, 1, 1, 1};
  GLfloat diffuse[] = {1, 1, 1, 1};

  glClearColor(0.1,0.1,0.1,1.0);
  glClearDepth(10000000);

  /* Set up Lighting */
  glLightfv(GL_LIGHT0, GL_POSITION, light_position);
  glLightfv(GL_LIGHT0, GL_DIFFUSE, diffuse);
  glLightfv(GL_LIGHT0, GL_SPECULAR, specular);
  glLightf(GL_LIGHT0, GL_CONSTANT_ATTENUATION, c);
  glLightf(GL_LIGHT0, GL_LINEAR_ATTENUATION, l);
  glLightf(GL_LIGHT0, GL_QUADRATIC_ATTENUATION, q);
  
  glEnable(GL_LIGHTING);
  glEnable(GL_LIGHT0);
  glDepthFunc(GL_LESS);
  glEnable(GL_DEPTH_TEST);
  glShadeModel(GL_SMOOTH);
  printf("Attenuation test. Usage\nc,C constant term\n");
  printf("l,L linear term\n");
  printf("q,Q quadratic term\n");
}


void Display(void)
{
}

void Idle(void)
{
  GLfloat sunSpec[] = {1, 1, 0, 1.0};
  GLfloat sunDiff[] =  {1, 1, 0, 1.0};
  GLfloat sunShi[] = {50.0};
  GLfloat earthSpec[] = {0, 0.5, 1, 1.0};
  GLfloat earthDiff[] =  {0, 0.5, 1, 1.0};
  GLfloat earthShi[] = {50.0};
  GLfloat moonSpec[] = {1, 1, 1, 1.0};
  GLfloat moonDiff[] =  {0.5, 0.5, 0.5, 1.0};
  GLfloat moonShi[] = {50.0};
     
     
     
   static GLfloat time;

   glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
   glPushMatrix();
	   glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR,  sunSpec);
	   glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE,   sunDiff);
	   glMaterialfv(GL_FRONT_AND_BACK, GL_SHININESS, sunShi);
	   glutSolidSphere(0.7,20,20);   

	   glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR,  earthSpec);
	   glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE,   earthDiff);
	   glMaterialfv(GL_FRONT_AND_BACK, GL_SHININESS, earthShi);
	   glColor3ub(0,255,0);	//Earth
	   glRotatef(time/180, 0, 1, 0);
	   glTranslatef(2,0,0);
	   glRotatef(time/10.f,0.0,1.0,0.0);
	   glutSolidSphere(0.2,10,8);  

	   glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR,  moonSpec);
	   glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE,   moonDiff);
	   glMaterialfv(GL_FRONT_AND_BACK, GL_SHININESS, moonShi);
	   glRotatef(-time/10.f,0.0,1.0,0.0);
	   glRotatef(15,1,0.0,0.0);
	   glRotatef(time/28,0.0,1.0,0.0);
	   glTranslatef(1,0,0);  //Moon
	   glRotatef(time/28,0.0,1.0,0.0);
	   glColor3ub(0,255,255);
	   glutWireTeapot(0.1);  
   glPopMatrix();
   time +=150;
   glutSwapBuffers();
}

void Reshape (int w, int h)
{
   glViewport (0, 0, (GLsizei) w, (GLsizei) h); 
   glMatrixMode (GL_PROJECTION);
   glLoadIdentity ();
   gluPerspective(60.0, (GLfloat) w/(GLfloat) h, 1.0, 20.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
   gluLookAt(0.0,0.0,5.0,0.0,0.0,0.0,0.0,1.0,0.0);
}

void Kbd(unsigned char key, int x, int y)
{
	switch (key){
	 case 27:  exit(0);break;
	 case 'c': c-=K;break;
	 case 'C': c+=K;break;
	 case 'l': l-=K;break;
	 case 'L': l+=K;break;
	 case 'q': q-=K;break;
	 case 'Q': q+=K;break;
	}
    if (q<0) q=0;
	if (l<0) l=0;
	if (c<0) c=0;
    glLightf(GL_LIGHT0, GL_CONSTANT_ATTENUATION, c);
    glLightf(GL_LIGHT0, GL_LINEAR_ATTENUATION, l);
    glLightf(GL_LIGHT0, GL_QUADRATIC_ATTENUATION, q);
	printf("Attenuation c=%f l=%f, q=%f\n",c,l,q);
}

int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGBA|GLUT_DEPTH);
   glutInitWindowSize(500,500); 
   glutInitWindowPosition(100,100);
   glutCreateWindow("Attenuation");
   glutDisplayFunc(Display); 
   glutIdleFunc(Idle); 
   glutReshapeFunc(Reshape);
   glutKeyboardFunc(Kbd);
   Init();
   glutMainLoop();
   return 0;
}