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Input and Interaction

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Input Devices Physical input devices

Keyboard devices and pointing devices Logical input devices

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Pointing Devices – 1/2 Mouse

Mechanical versus optical Trackball Trackpoint

(Pressure-sensitive) Data tablet

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Pointing Devices – 2/2 Lightpen

Light-sensing device

Joystick Two velocities Variable-sentivity device Haptic device

Spaceball Six degrees of freedom

Data gloves

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Positioning

Relative Mouse, trackball, trackpoint

Absolute Data tablet

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Logical Input Devices – 1/2 Characteristics

The measurements returned to the programs The time these measurements returned

Six classes

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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 use

s of a locator, could be implemented by a “mouse dragging”

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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

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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)

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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();}

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Display and Idle CallBacks glutDisplay(display); Idle callback: is invoked when there is no o

ther events Callback could be changed at any time or d

isabled by set to NULL

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A Program Example: Drawing Squares with Mouse?

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A Program Example: Drawing Squares with Mouse

Demo

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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

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A Simple Paint Program – 2/4

Initial display of paint program Menu structure of paint program

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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…

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A Simple Paint Program – 4/4

Demo

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Animating Interacitve Programs A Rotating Square – 1/4

x=cosy=sin

(cos, sin ), (-sin, cos), (-cos, -sin), (sin, -cos) lie on the unit circle

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A Rotating Square 2/2Demo

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Double Buffering How to avoid flickering?

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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

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Rubberbanding

Demo

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Logic Operation Copy or replacement mode There are 16 possible operations between 2 bits Source pixel and destination pixel d=ds, where means XOR (exclusive or)

d=(ds) 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 */

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