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Interaction I

Interaction I. Allowing the user to interact with the system. Interaction through keyboard or mouse For example to exit when you hit esc The keyboard and mouse call back functions are called using: glutKeyboardFunc (keyboard); glutMouseFunc (mouse);

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Interaction I

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  1. Interaction I • Allowing the user to interact with the system. • Interaction through keyboard or mouse • For example to exit when you hit esc • The keyboard and mouse call back functions are called using: glutKeyboardFunc(keyboard); glutMouseFunc(mouse); called in the main program before the glMainloop • The keyboard and mouse functions are user defined function

  2. Example of the keyboard function void keyboard(unsigned char key, int x, int y) {/* Details follows*/ if(key==27) exit(1); if (key == 'a') {if(++Theta > 359) Theta = 0;} else if(key == 's') {if(--Theta < 0) Theta = 359;} glutPostRedisplay(); }

  3. Keyboard Interaction • Theta is a global integer variable defining the angle of rotation • The function changes the global variable Theta according to the key pressed and redisplay or repaint the window • If the key pressed is the ESC exit the application • If ‘a’ is pressed the rotation is clockwise (increment Theta) • If ‘s’ is pressed the rotation is counter (Decrement Theta) • glutPostRedisplay(); • call the display function again. • we can not call display directly.

  4. Mouse Example void mouse(int button, int state, int x, int y) { if(state == GLUT_DOWN) { if(button==GLUT_LEFT_BUTTON) {if(++Theta > 359) Theta = 0;} else /* GLUT_RIGHT */ {if(--Theta< 0) Theta = 359;} } } else { /* GLUT_UP */ } glutPostRedisplay(); }

  5. Mouse interaction • glutMouseFunc(mouse); is the call back function • If a mouse is clicked there are two possibilities: The left button or the right one • Also when it is released, there could be some action for example redrew the window.

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