CS184 Section 1
Introduction/Simple OpenGL

example_00

int main(int argc, char *argv[]) {
    //This initializes glut
    glutInit(&argc, argv);

    //This tells glut to use a double-buffered window with RGB channels 
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);

    // Initalize theviewport size
    viewport.w = 400;
    viewport.h = 400;

    //The size and position of the window
    glutInitWindowSize(viewport.w, viewport.h);
    glutInitWindowPosition(0, 0);
    glutCreateWindow("CS184!");

    initScene();                     // quick function to set up scene

                                     // functions to run when...
    glutDisplayFunc(myDisplay);      // it's time to draw something
    glutReshapeFunc(myReshape);      // window gets resized
    glutIdleFunc(myFrameMove);       // not handling any other task
    glutMainLoop();                  // infinite loop
    return 0;
  }
    

example_00

void myReshape(int w, int h) {
  viewport.w = w;
  viewport.h = h;

  // sets the rectangle that will be the window
  glViewport(0,0,viewport.w,viewport.h);
  glMatrixMode(GL_PROJECTION);

  // loading the identity matrix for the screen
  glLoadIdentity();                

  // glOrtho sets left, right, bottom, top, zNear, zFar of the chord system

  // glOrtho(-1, 1 + (w-400)/200.0 , -1 -(h-400)/200.0, 1, 1, -1); // add
  // glOrtho(-w/400.0, w/400.0, -h/400.0, h/400.0, 1, -1); // center

  glOrtho(-1, 1, -1, 1, 1, -1);    // resize type = stretch

}

example_00

void myDisplay() {
  // This is a quick hack to add a little bit of animation.
  static float tip = 0.5f;
  const  float stp = 0.0001f;
  const  float beg = 0.1f;
  const  float end = 0.9f;

  tip += stp;
  if (tip>end) tip = beg;

  glClear(GL_COLOR_BUFFER_BIT);                // clear the color buffer (sets everything to black)

  glMatrixMode(GL_MODELVIEW);                  // indicate we are specifying camera transformations
  glLoadIdentity();                            // make sure transformation is "zero'd"

...

example_00

  //----------------------- code to draw objects --------------------------
  // Rectangle Code
  //glColor3f(red component, green component, blue component);
  glColor3f(1.0f,0.0f,0.0f);                   // setting the color to pure red 90% for the rect

  glBegin(GL_POLYGON);                         // draw rectangle 
  //glVertex3f(x val, y val, z val (won't change the point because of the projection type));
  glVertex3f(-0.8f, 0.0f, 0.0f);               // bottom left corner of rectangle
  glVertex3f(-0.8f, 0.5f, 0.0f);               // top left corner of rectangle
  glVertex3f( 0.0f, 0.5f, 0.0f);               // top right corner of rectangle
  glVertex3f( 0.0f, 0.0f, 0.0f);               // bottom right corner of rectangle
  glEnd();
  // Triangle Code
  glColor3f(1.0f,0.5f,0.0f);                   // setting the color to orange for the triangle

  float basey = -sqrt(0.48f);                  // height of triangle = sqrt(.8^2-.4^2)
  glBegin(GL_POLYGON);
  glVertex3f(tip,  0.0f, 0.0f);                // top tip of triangle
  glVertex3f(0.1f, basey, 0.0f);               // lower left corner of triangle
  glVertex3f(0.9f, basey, 0.0f);               // lower right corner of triangle
  glEnd();
  //-----------------------------------------------------------------------

  glFlush();
  glutSwapBuffers();                           // swap buffers (we earlier set double buffer)
}

example_00

void initScene(){
  glClearColor(0.0f, 0.0f, 0.0f, 0.0f); // Clear to black, fully transparent

  myReshape(viewport.w,viewport.h);
}

void myFrameMove() {
  //nothing here for now
  glutPostRedisplay(); // forces glut to call the display function (myDisplay())
}

Now... Do something interesting!