gl-sand-clocks.pas

//{$apptype GUI}

uses Gl, Glu, Glut;

const width = 600;
      height = 600;

var rotation: integer;

procedure display;
cdecl;
begin
  glClear(GL_COLOR_BUFFER_BIT or GL_DEPTH_BUFFER_BIT);
  glLoadIdentity();
  
  glRotatef(rotation, 0.0, 0.0, 1.0);

  //top triangle
  
  glBegin(GL_TRIANGLES);
    glColor3f(1.0, 1.0, 0.0); // rgb
    glVertex3f(-1.2, 2.4, 0.0);
    glVertex3f(-1.8, 2.4, 0.0);
    glColor3f(1.0, 1.0, 1.0); // rgb
    glVertex3f(-1.5, 1.8, 0.0); //<--
  glEnd();

  //bottom triangle
  
  glBegin(GL_TRIANGLES);
    glColor3f(1.0, 1.0, 1.0); // rgb
    glVertex3f(-1.5, 1.8, 0.0); //<--
    glColor3f(0.0, 1.0, 1.0); // rgb
    glVertex3f(-1.8, 1.2, 0.0);
    glVertex3f(-1.2, 1.2, 0.0);
  glEnd();
  
  glFlush();
end;

procedure rotate;
begin
  rotation := rotation + 1;
  display();
end;

procedure keyboard(code: byte; x, y: longint);
cdecl;
begin
  case code of
    27: halt;
    32: rotate();
  end;
end;

procedure initGl;
begin
  //glClearColor(0.0, 0.0, 0.0, 0.0);
  
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(-4, 4, -4*height/width, 4*height/width, -4, 4);
  
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  
  // Z!
  glClearDepth(1.0);
  glEnable(GL_DEPTH_TEST);
  glDepthFunc(GL_LEQUAL);
end;

procedure initGlut;
begin
  glutInitDisplayMode(GLUT_SINGLE or GLUT_RGB);
  glutInitWindowSize(width, height);
  glutCreateWindow('HW');
  glutDisplayFunc(@display);
  glutKeyboardFunc(@keyboard);
end;

Begin
  initGlut;
  initGl;
  glutMainLoop();
End.