HOW TO OPEN THE WINDOW FOR DRAWING?? (OpenGL utility library)

Open the window for drawing:

Here is the sample code for opening window for drawing using OpenGL Toolkit. 

code for intializiation window for drawing :

int main(int argc, char **argv)

{

glutInit(&argc, argv);                                                      // initializes the toolkit

glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);     //set the display mode

glutInitWindowSize(640,480);                                      //set the window size

glutInitWindowPosition(100,100);                       //set the window position on screen

glutCreateWindow(“MyProgram”);                   //open the screen window

/* register callback functions */

myInit();                                                             // additional initializations, if necessary

glutMainLoop();                                             //go into a perpetual loop

}

Note: 

          the argument of glutinit() and main() must be same.

Define myInit();  function:

void myInit(void)

{

glClearColor(1.0,1.0,1.0,0.0);

glColor3f(0.0f,0.0f,0.0f);

glPointSize(4.0);

glMatrixMode(GL_PROJECTION);

glLoadIdentity();

gluOrtho2D(0.0,640.0,0.0,480.0);

}

OpenGL Events:

There are four main types of event functions that we work with in OpenGL.

int main(int argc, char **argv)

{

/* initialize basic things */

/* register callback functions */

glutDisplayFunc(myDisplay);                     //register the redraw function

glutReshapeFunc(myReshape);                //register the reshape function

glutMouseFunc(myMouse);                       //register the mouse action function

glutKeyboardFunc(myKeyboard);           //register the keyboard action function

/* end register callback functions */

/* may be more initializations */

glutMainLoop();                                            //enter the unending main loop

}

glutDisplayFunc(myDisplay):

 Windows issues a “redraw” event when it determines that a window should be redrawn on the screen. This happens when a window is first opened. Here myDisplay() is a registered callback function for the redraw event.

glutReshapeFunc(myReshape):

 Screen windows can be reshaped by a user, by resizing the windows. So myReshape() is registered with the reshape event.

glutMouseFunc(myMouse):

 This command registers the myMouse() function. It is called whenever a mouse event occurs like click. myMouse() is automatically passed arguments telling the exact position of mouse and the nature of action initiated.

glutKeyboardFunc(myKeyboard):

 This command registers the myKeyboard() function with the event of pressing or releasing any key on the keyboard.

Color in OpenGL:

Initialize color buffer before you use colors. You need to set the color value. You can

use the function glColor3f(red, green, blue) for this purpose. For example

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

                                                               // Clear The Screen And The Depth Buffer

glLoadIdentity();                                  // Reset The Current Modelview Matrix

glBegin(GL_TRIANGLES);                   // Begin Drawing Triangles

glColor3f(1.0,1.0,1.0)                           //set white color

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