Pointing device

A pointing device is a human interface device that allows a user to input spatial (i.e., continuous and multi-dimensional) data to a computer. Graphical user interfaces (GUI) and CAD systems allow the user to control and provide data to the computer using physical gestures by moving a hand-held mouse or similar device across the surface of the physical desktop and activating switches on the mouse. Movements of the pointing device are echoed on the screen by movements of the pointer (or cursor) and other visual changes. Common gestures are point and click and drag and drop.

This article is about computer pointing devices. For the measuring tool used to copy sculptures, see Pointing machine.

While the most common pointing device by far is the mouse, many more devices have been developed. However, the term mouse is commonly used as a metaphor for devices that move a computer cursor.

Fitts's law can be used to predict the speed with which users can use a pointing device.

direct vs. indirect input

To classify several pointing devices, a certain number of features can be considered. For example, the device's movement, controlling, positioning or resistance. The following points should provide an overview of the different classifications.^[1]

In case of a direct-input pointing device, the on-screen pointer is at the same physical position as the pointing device (e.g., finger on a touch screen, stylus on a tablet computer). An indirect-input pointing device is not at the same physical position as the pointer but translates its movement onto the screen (e.g., computer mouse, joystick, stylus on a graphics tablet).

An absolute-movement input device (e.g., stylus, finger on touch screen) provides a consistent mapping between a point in the input space (location/state of the input device) and a point in the output space (position of pointer on screen). A relative-movement input device (e.g., mouse, joystick) maps displacement in the input space to displacement in the output state. It therefore controls the relative position of the cursor compared to its initial position.

An isotonic pointing device is movable and measures its displacement (mouse, pen, human arm) whereas an isometric device is fixed and measures the force which acts on it (trackpoint, force-sensing touch screen). An elastic device increases its force resistance with displacement (joystick).

A position-control input device (e.g., mouse, finger on touch screen) directly changes the absolute or relative position of the on-screen pointer. A rate-control input device (e.g., trackpoint, joystick) changes the speed and direction of the movement of the on-screen pointer.

Another classification is the differentiation between whether the device is physically translated or rotated.

Different pointing devices have different degrees of freedom (DOF). A computer mouse has two degrees of freedom, namely its movement on the x- and y-axis. However the Wiimote has 6 degrees of freedom: x-, y- and z-axis for movement as well as for rotation.

As mentioned later in this article, pointing devices have different possible states. Examples for these states are out of range, tracking or dragging.

Examples

MT is the average time to complete the movement.

a and b are constants that depend on the choice of input device and are usually determined empirically by regression analysis.

ID is the index of difficulty.

D is the distance from the starting point to the center of the target.

W is the width of the target measured along the axis of motion. W can also be thought of as the allowed error tolerance in the final position, since the final point of the motion must fall within ±W⁄2 of the target's center.

A is a device similar to a touch screen, but uses a special light-sensitive pen instead of the finger, which allows for more accurate screen input. As the tip of the light pen makes contact with the screen, it sends a signal back to the computer containing the coordinates of the pixels at that point. It can be used to draw on the computer screen or make menu selections, and does not require a special touch screen because it can work with any CRT display.

light pen

Light gun

Palm mouse – held in the palm and operated with only two buttons; the movements across the screen correspond to a feather touch, and pressure increases the speed of movement

– sometimes called a mole – a mouse variant for those who do not wish to or cannot use the hands or the head; instead, it provides footclicks

Footmouse

Puck, similar to a mouse, but designed for absolute positioning rather than relative. It typically has a transparent plastic with crosshairs for precise positioning and tracing. Pucks are most commonly used for tracing in CAD/CAM/CAE work.

devices – a mouse controlled by the user's retinal movements, allowing cursor-manipulation without touch

Eye tracking

Finger-mouse – An extremely small mouse controlled by two fingers only; the user can hold it in any position

Gyroscopic mouse – a senses the movement of the mouse as it moves through the air. Users can operate a gyroscopic mouse when they have no room for a regular mouse or must give commands while standing up. This input device needs no cleaning and can have many extra buttons, in fact, some laptops doubling as TVs come with gyroscopic mice that resemble, and double as, remotes with LCD screens built in.

gyroscope

– can be thought of as a 1D pointing device – see also steering wheel section of game controller article

Steering wheel

– another 1D pointing device

Paddle

– another 1D pointing device

Jog dial

Yoke (aircraft)

Some high- input devices

degree-of-freedom

– six-degree controller

3Dconnexion

Discrete pointing devices

– a very simple keyboard

directional pad

– used to point at gross locations in space with feet

Dance pad

– a handheld, position-based pointing device based on existing wireless optical mouse technology