/*
 * smooth.c
 * This program demonstrates smooth shading.
 * A smooth shaded polygon is drawn in a 2-D projection.
 * From OpenGL Programming Guide
 */
#include <stdlib.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>

void init(void) 
{
  glClearColor (0.0, 0.0, 0.0, 0.0);

  glShadeModel (GL_FLAT);
  /* glShadeModel (GL_SMOOTH); */
}

void triangle(void)
{
  glBegin (GL_TRIANGLES);
  glColor3f (1.0, 0.0, 0.0); /* red */
  glVertex2f (5.0, 5.0);
  glColor3f (0.0, 1.0, 0.0); /* green */
  glVertex2f (25.0, 5.0);
  glColor3f (0.0, 0.0, 1.0); /* blue */
  glVertex2f (5.0, 25.0);
  glEnd();
}

void display(void)
{
  glClear (GL_COLOR_BUFFER_BIT); /* clear buffer */
  triangle ();			/* draw triangle */
  glFlush ();			/* force display */
}

void reshape(int w, int h)
{
  glViewport (0, 0, (GLsizei) w, (GLsizei) h);
  glMatrixMode (GL_PROJECTION);
  glLoadIdentity ();
  if (w <= h)
    gluOrtho2D (0.0, 30.0, 0.0, 30.0 * (GLfloat) h/(GLfloat) w);
  else
    gluOrtho2D (0.0, 30.0 * (GLfloat) w/(GLfloat) h, 0.0, 30.0);
  glMatrixMode(GL_MODELVIEW);
}

void keyboard(unsigned char key, int x, int y)
{
  switch (key) {
  case 27:
    exit(0);
    break;
  }
}

int main(int argc, char** argv)
{
  glutInit(&argc, argv);
  glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
  glutInitWindowSize (500, 500); 
  glutInitWindowPosition (100, 100);
  glutCreateWindow (argv[0]);
  init ();
  /* set callback function */
  glutDisplayFunc(display); 
  glutReshapeFunc(reshape);
  glutKeyboardFunc (keyboard);
  glutMainLoop();
  return 0;
}