1. 1 Input and Interaction

2. 2 Input Devices Physical input devices Keyboard devices and pointing devices Logical input devices

3. 3 Pointing Devices – 1/2 Mouse Mechanical versus optical Trackball Trackpoint (Pressure-sensitive) Data tablet

4. 4 Pointing Devices – 2/2 Lightpen Light-sensing device Joystick Two velocities Variable-sentivity device Haptic device Spaceball Six degrees of freedom Data gloves

5. 5 Positioning Relative Mouse, trackball, trackpoint Absolute Data tablet

6. 6 Logical Input Devices – 1/2 Characteristics The measurements returned to the programs The time these measurements returned Six classes

7. 7 Logical Input Devices – 2/2 String: by keyboard Locator: by mouse or trackball Pick: id of the selected object is returned Choice: select one of a distinct number of options, e.g. menus Dial or valuators: e.g. slidebars Stroke: returns an array of locations: multiple uses of a locator, could be implemented by a “mouse dragging”

8. 8 Clients and Servers Servers: provide services Print servers, file servers, graphics servers… Clients: users and user programs that make use of these services OpenGL application programs

9. 9 Programming Event-Driven Input Using the pointing device Move event Mouse is moved and one of the button pressed Passive move event Mouse is moved and no buttons are pressed Mouse event: one of mouse buttons is pressed or released glutMouseFunc(mouse): register the function void mouse(int button, int state, int x, int y)

10. 10 Other Events and CallBacks Reshape event: whenever the window is resized glutReshapeFunc(myReshape); Motion event: glutMotionFunc(drawSquare); Keyboard event: glutKeyboardFunc(keyboard); void keyboard(unsigned char key, int x, int y) { if(key==‘q’ || key == ‘Q’) exit(); }

11. 11 Display and Idle CallBacks glutDisplay(display); Idle callback: is invoked when there is no other events Callback could be changed at any time or disabled by set to NULL

12. 12 A Program Example: Drawing Squares with Mouse?

13. 13 A Program Example: Drawing Squares with Mouse Demo

14. 14 A Simple Paint Program – 1/4 Draw geometric primitives: line segments, polygons Manipulate pixels Control attributes of primitives Include menus Should behave correctly when moved or resized

15. 15 A Simple Paint Program – 2/4 Initial display of paint program Menu structure of paint program

16. 16 A Simple Paint Program – 3/4 Five drawing modes: line segment, rectangle, triangle, pixel, and text Two (or three) clicks determine the locations of the end points of line segments, rectangles… Choose colors, pixel size, fill patterns…

17. 17 A Simple Paint Program – 4/4 Demo

18. 18 Animating Interacitve Programs A Rotating Square – 1/4 x=cos  y=sin  (cos , sin  ), (-sin , cos  ), (-cos , -sin  ), (sin , -cos  ) lie on the unit circle

19. 19 A Rotating Square 2/2 Demo

20. 20 Double Buffering How to avoid flickering?

21. 21 Design of Interactive Programs A smooth display with no flickering A variety of interactive devices A variety of methods for entering and displaying information An easy-to-use interface Feedback to the user Tolerance for user error Consider human factors

22. 22 Rubberbanding Demo

23. 23 Logic Operation Copy or replacement mode There are 16 possible operations between 2 bits Source pixel and destination pixel d=d  s, where  means XOR (exclusive or) d=(d  s)  s, which means drawing something twice will erase it OpenGL support all 16 logic modes, GL_COPY is the default glEnable(GL_COLOR_LOGIC_OP); glLogicOP(GL_XOR); /* change it to XOR mode */

24. 24 Summary and Notes Input devices Event mode and callbacks Sample interaction code Double buffering XOR and Rubberbanding