// Shows the fully saturated colorwheel in a main window.

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

const double pi = std::acos(-1.0);

// Clears the current window and draws the wheel.
void display() {
  const int N = 600;            // Number of fans
  double delta = 6.0 / N;       // Amount by which to vary color component
  double theta = 0.0;           // Current angle

  // Start with red at 0 radians.
  GLfloat red = 1;
  GLfloat green = 0;
  GLfloat blue = 0;

  glClear(GL_COLOR_BUFFER_BIT);
  glBegin(GL_TRIANGLE_FAN);

  // Start the triangle fan with a white center point
  glColor3f(1, 1, 1);
  glVertex3f(0, 0, 0);

  // For N triangles we need N+1 vertices
  for (int i = 0; i <= N; i++) {
    if (i > 5*N/6) blue -= delta;
    else if (i > 4*N/6) red += delta;
    else if (i > 3*N/6) green -= delta;
    else if (i > 2*N/6) blue += delta;
    else if (i > 1*N/6) red -= delta;
    else green += delta;
    glColor3f(red, green, blue);
    glVertex3f(cos(theta), sin(theta), 0);
    theta += 2.0 * pi / N;
  }

  glEnd();
  glFlush();
}

// Run the application.
int main(int argc, char** argv) {
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
  glutInitWindowPosition(80, 80);
  glutInitWindowSize(500, 500);
  glutCreateWindow("The Color Wheel");
  glutDisplayFunc(display);
  glutMainLoop();
}

// A funky, psychedelic square.

#include <cstdlib>
#include <ctime>
#ifdef __APPLE_CC__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif

const int WIDTH = 10;

static GLfloat colors[WIDTH + 1][WIDTH + 1][3];

// Clears the window and draws the square.
void display() {

  glClear(GL_COLOR_BUFFER_BIT);

  for (int strip = 0; strip < WIDTH; strip++) {
    glBegin(GL_QUAD_STRIP);
    for (int v = 0; v < (WIDTH + 1) * 2; v++) {
      int x = v / 2;
      int z = (v & 1) ? strip + 1 : strip;
      glColor3fv(colors[x][z]);
      glVertex3i(x, 0, z);
    }
    glEnd();
  }
  glFlush();
}

// Sets up global attributes like clear color and drawing color, and sets up
// the desired projection and modelview matrices.
void init() {

  // Seed the random number generator.
  srand((unsigned)time(0));

  // Fill in the color table with random colors.
  for (int i = 0; i <= WIDTH; i++) {
    for (int j = 0; j <= WIDTH; j++) {
      for (int k = 0; k < 3; k++) {
        colors[i][j][k] = (float)rand()/(float)RAND_MAX;
      }
    }
  }

  // Black background for coolness.
  glClearColor(0.0, 0.0, 0.0, 1.0);

  // Set the camera lens to have a 70 degree (vertical) field of view, an
  // aspect ratio of 4/3, and have everything closer than 1 unit to the
  // camera and greater than 40 units distant clipped away.
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluPerspective(70.0, 4.0/3.0, 1, 40);

  // Position camera at (4, 7, 5) looking at (0, 0, 0) with the vector
  // <0, 1, 0> pointing upward.
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  gluLookAt(4, 7, 5, 0, 0, 0, 0, 1, 0);

  // We defined the square from 0-10 in x and 0-10 in z, but we want (0,0,0)
  // in the center, so move it.
  glTranslated(-5, 0, -5);
}

// Runs the app.
int main(int argc, char** argv) {
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
  glutInitWindowPosition(80, 80);
  glutInitWindowSize(800, 600);
  glutCreateWindow("An insipid square");
  glutDisplayFunc(display);
  init();
  glutMainLoop();
}