/* code by Iolaire McKinnon <iolaire@iolaire.com. Please give credit if you reuse. From http://iolaire.com */
#include <GL/glut.h>
#include <stdlib.h>
#include <math.h>

#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif

static int
	j = 0,
	size = 40,
	lambda = 10,
	i,
	a,
	doPoints = 0,
	direction = 1;

static float c, xaxis, xoffset, zaxis, shiny;

void
initlights(void)
{
    GLfloat ambient[] =
    {0.2, 0.2, 0.2, 1.0};
    GLfloat position[] =
    {1.0, 3.0, 4.0, 1.0};

    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);

    glLightfv(GL_LIGHT0, GL_AMBIENT, ambient);
    glLightfv(GL_LIGHT0, GL_POSITION, position);

}

void myinit(void)
{
	GLfloat fogColor[4] = {0.2, 0.1, 0.8, 1.0};

   glEnable(GL_FOG);
   glFogi (GL_FOG_MODE, GL_LINEAR);
   glHint (GL_FOG_HINT, GL_NICEST);  /*  per pixel   */
   glFogf (GL_FOG_START, 2.0);
   glFogf (GL_FOG_END, 10.0);
   glFogfv (GL_FOG_COLOR, fogColor);
   glClearColor(0.0, 0.0, 0.0, 1.0);

   glDepthFunc(GL_LESS);
   glEnable(GL_DEPTH_TEST);
   glShadeModel(GL_SMOOTH);
	initlights();
}

void display(void)
{
	if (lambda < 1) { lambda = 1; }
	if (lambda > 40) { lambda = 40; }
	if (shiny < 0) { shiny = 0; }

	GLfloat mat_diffuse[] =
    {0.6, 0.6, 0.6, 1.0};
    GLfloat mat_specular[] =
    {1.0, 1.0, 1.0, 0.2};
    GLfloat mat_shininess[] =
    {shiny};

    glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
    glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
    glMaterialfv(GL_FRONT, GL_SHININESS, mat_shininess);

	glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glColor3f(1.0, 1.0, 0.0);
	glPointSize(4.0);

	if(doPoints) { glBegin(GL_POINTS); }
	else { glBegin(GL_TRIANGLES);   }
   c = sin(j*M_PI/180.0);
   for (a = 1; a < size; a++) {

	   for (i = 1; i < size; i++) {
		   // Triangle 1
		   c = sin((j + (lambda * i)) * (M_PI / 180.0));
		   xoffset = cos((j + (lambda * i)) * (M_PI / 180.0));
		   xaxis = (float) i + xoffset;
		   zaxis = (float) a;
		   glVertex3f(xaxis, c, zaxis); //start

		   c = sin((j + (lambda * (i+1))) * (M_PI / 180.0));
		   xoffset = cos((j + (lambda * (i+1))) * (M_PI / 180.0));
		   xaxis = (float) (i+1) + xoffset;
		   zaxis = (float) a;
		   glVertex3f(xaxis, c, zaxis); // 1 up x

		   c = sin((j + (lambda * i)) * (M_PI / 180.0));
		   xoffset = cos((j + (lambda * i)) * (M_PI / 180.0));
		   xaxis = (float) i + xoffset;
		   zaxis = (float) a+1;
		   glVertex3f(xaxis, c, zaxis); // 1 up z

			//	   Triangle2
		   c = sin((j + (lambda * i)) * (M_PI / 180.0));
		   xoffset = cos((j + (lambda * i)) * (M_PI / 180.0));
		   xaxis = (float) i + xoffset;
		   zaxis = (float) a+1;
		   glVertex3f(xaxis, c, zaxis); // 1 up z

		   c = sin((j + (lambda * (i+1))) * (M_PI / 180.0));
		   xoffset = cos((j + (lambda * (i+1))) * (M_PI / 180.0));
		   xaxis = (float) (i+1) + xoffset;
		   zaxis = (float) a;
		   glVertex3f(xaxis, c, zaxis); // 1 up x

		   c = sin((j + (lambda * (i+1))) * (M_PI / 180.0));
		   xoffset = cos((j + (lambda * (i+1))) * (M_PI / 180.0));
		   xaxis = (float) (i+1) + xoffset;
		   zaxis = (float) a+1;
		   glVertex3f(xaxis, c, zaxis); // 1 up x and z

/*
35------6
|\\     |
| \\ T2 |
|  \\   |
|   \\  |   Layout
| T1 \\ |
| 	  \\|
1------24
*/
	   }

   }
	   glEnd();

   j++;

   glutSwapBuffers();

}

void reshape (int w, int h)
{
   glViewport (0, 0, (GLsizei) w, (GLsizei) h);
   glMatrixMode (GL_PROJECTION);
   glLoadIdentity ();
   gluPerspective(80.0, (GLfloat) w/(GLfloat) h, 1.0, 20.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
   glTranslatef (-20.0, -3.0, -30.0);
}

/* ARGSUSED1 */
void keyboard (unsigned char key, int x, int y)
{
   switch (key) {
      case 'z':
         lambda = lambda + 1;
         glutPostRedisplay();
         break;
      case 'x':
         lambda = lambda - 1;
         glutPostRedisplay();
         break;
      case ',':
         shiny = shiny + 1;
         glutPostRedisplay();
         break;
      case '.':
         shiny = shiny - 1;
         glutPostRedisplay();
         break;
      case 'p':
         doPoints = !doPoints;
         glutPostRedisplay();
         break;
      case 27:
         exit(0);
         break;
      default:
         break;
   }
}

int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
   glutInitWindowSize (500, 500);
   glutInitWindowPosition (100, 100);
   glutCreateWindow (argv[0]);
   myinit ();
   glutDisplayFunc(display);
   glutReshapeFunc(reshape);
   glutKeyboardFunc(keyboard);
   glutIdleFunc(display);
   glutMainLoop();
   return 0;
}