////////////////////////////////////////////////////////////
// checkeredFloor.cpp
//
// This program uses flat shading to draw a checkered floor.
//
// Sumanta Guha
////////////////////////////////////////////////////////////

#include <iostream>

#ifdef __APPLE__
#  include <GLUT/glut.h>
#else
#  include <GL/glut.h>
#endif

using namespace std;

// Initialization routine.
void setup(void)
{    
   glClearColor(1.0, 1.0, 1.0, 0.0);
   glEnable(GL_DEPTH_TEST); // Enable depth testing.

   // Turn on OpenGL lighting.
   glEnable(GL_LIGHTING);    

   // Light property vectors.
   float lightAmb[] = { 0.0, 0.0, 0.0, 1.0 };
   float lightDifAndSpec[] = { 1.0, 1.0, 1.0, 1.0 };
   float lightPos[] = {0.0, 1.0, 0.0, 0.0 };
   float globAmb[] = { 0.2, 0.2, 0.2, 1.0 };

   // Light properties.
   glLightfv(GL_LIGHT0, GL_AMBIENT, lightAmb);
   glLightfv(GL_LIGHT0, GL_DIFFUSE, lightDifAndSpec);
   glLightfv(GL_LIGHT0, GL_SPECULAR, lightDifAndSpec);
   glLightfv(GL_LIGHT0, GL_POSITION, lightPos);

   glEnable(GL_LIGHT0); // Enable particular light source.
   glLightModelfv(GL_LIGHT_MODEL_AMBIENT, globAmb); // Global ambient light.

	// Material property vectors.
   float matSpec[] = { 1.0, 1.0, 1.0, 1.0 };
   float matShine[] = { 50.0 };

   // Material properties.
   glMaterialfv(GL_FRONT, GL_SPECULAR, matSpec);
   glMaterialfv(GL_FRONT, GL_SHININESS, matShine);

   // Enable color material mode.
   glEnable(GL_COLOR_MATERIAL); 
   glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE); 
   
   // Flat shading to obtain the checkered pattern of the floor.
   glShadeModel(GL_FLAT);

   // Cull back faces.
   glEnable(GL_CULL_FACE);
   glCullFace(GL_BACK);
}

// Drawing routine.
void drawScene(void)
{
   int i;
   float z;

   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

   glLoadIdentity();
   gluLookAt(0.0, 5.0, 30.0, 0.0, 10.0, 0.0, 0.0, 1.0, 0.0);

   // Draw floor as a stack of triangle strips.
   i = 0;
   for(z = 100.0; z > -100.0; z -= 5.0)
   {
      glBegin(GL_TRIANGLE_STRIP);
      for(float x = -100.0; x < 100.0; x += 5.0)
	  {
         if (i % 2) glColor4f(0.0, 0.5, 0.5, 1.0); 
         else glColor4f(1.0, 1.0, 1.0, 1.0); 
         glNormal3f(0.0, 1.0, 0.0);
		 glVertex3f(x, 0.0, z - 5.0);
	     glVertex3f(x, 0.0, z);
		 i++;
	  }
      glEnd();
	  i++;
   }

   glFlush();	
}

// OpenGL window reshape routine.
void resize(int w, int h)
{
   glViewport(0, 0, (GLsizei)w, (GLsizei)h);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glFrustum(-5.0, 5.0, -5.0, 5.0, 5.0, 100.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
}

// Keyboard input processing routine.
void keyInput(unsigned char key, int x, int y)
{
   switch(key) 
   {
      case 27:
         exit(0);
         break;
      default:
         break;
   }
}

// Main routine.
int main(int argc, char **argv) 
{
   glutInit(&argc, argv);
   glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
   glutInitWindowSize(500, 500);
   glutInitWindowPosition(100, 100);
   glutCreateWindow("checkeredFloor.cpp");
   setup();
   glutDisplayFunc(drawScene);
   glutReshapeFunc(resize);
   glutKeyboardFunc(keyInput);
   glutMainLoop();

   return 0; 
}