A viewport is a polygon viewing region in

computer graphics Computer graphics deals with generating images with the aid of computers. Today, computer graphics is a core technology in digital photography, film, video games, cell phone and computer displays, and many specialized applications. A great de ...

. In

theory, there are two region-like notions of relevance when rendering some objects to an image. In textbook terminology, the '' world coordinate window'' is the area of interest (meaning what the user wants to visualize) in some application-specific coordinates, e.g. miles, centimeters etc. The word ''window'' as used here should not be confused with the GUI window, i.e. the notion used in

window manager A window manager is system software that controls the placement and appearance of windows within a windowing system in a graphical user interface. Most window managers are designed to help provide a desktop environment. They work in conjunctio ...

s. Rather it is an analogy with how a

window A window is an opening in a wall, door, roof, or vehicle that allows the exchange of light and may also allow the passage of sound and sometimes air. Modern windows are usually glazed or covered in some other transparent or translucent mat ...

limits what one can see outside a room. In contrast, the ''viewport'' is an area (typically rectangular) expressed in rendering-device-specific coordinates, e.g. pixels for screen coordinates, in which the objects of interest are going to be rendered. Clipping to the world-coordinates window is usually applied to the objects before they are passed through the window-to-viewport transformation. For a 2D object, the latter transformation is simply a combination of

translation Translation is the communication of the meaning of a source-language text by means of an equivalent target-language text. The English language draws a terminological distinction (which does not exist in every language) between ''transla ...

and scaling, the latter not necessarily uniform. An analogy of this transformation process based on traditional

photography Photography is the art, application, and practice of creating durable images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is emplo ...

notions is to equate the world-clipping window with the camera settings and the variously sized prints that can be obtained from the resulting film image as possible viewports. Because the physical-device-based coordinates may not be portable from one device to another, a software

abstraction layer In computing, an abstraction layer or abstraction level is a way of hiding the working details of a subsystem. Examples of software models that use layers of abstraction include the OSI model for network protocols, OpenGL, and other graphics libr ...

known as

normalized device coordinates Normalization or normalisation refers to a process that makes something more normal or regular. Most commonly it refers to: * Normalization (sociology) or social normalization, the process through which ideas and behaviors that may fall outside of ...

is typically introduced for expressing viewports; it appears for example in the

Graphical Kernel System The Graphical Kernel System (GKS) was the first ISO standard for low-level computer graphics, introduced in 1977. A draft international standard was circulated for review in September 1983. Final ratification of the standard was achieved in 1985 ...

(GKS) and later systems inspired from it. In

3D computer graphics 3D computer graphics, or “3D graphics,” sometimes called CGI, 3D-CGI or three-dimensional computer graphics are graphics that use a three-dimensional representation of geometric data (often Cartesian) that is stored in the computer for th ...

it refers to the 2D rectangle used to project the 3D scene to the position of a

virtual camera In 3D video games, a virtual camera system aims at controlling a camera or a set of cameras to display a view of a 3D virtual world. Camera systems are used in video games where their purpose is to show the action at the best possible angle; m ...

. A viewport is a region of the screen used to display a portion of the total image to be shown. In

virtual desktop In computing, a virtual desktop is a term used with respect to user interfaces, usually within the WIMP paradigm, to describe ways in which the virtual space of a computer's desktop environment is expanded beyond the physical limits of the ...

s, the viewport is the visible portion of a 2D area which is larger than the visualization device. When viewing a document in a

web browser A web browser is application software for accessing websites. When a user requests a web page from a particular website, the browser retrieves its files from a web server and then displays the page on the user's screen. Browsers are used o ...

, the viewport is the region of the browser window which contains the visible portion of the document. If the size of the viewport changes, for example as a result of the user resizing the browser window, then the browser may reflow the document (recalculate the locations and sizes of elements of the document). If the document is larger than the viewport, the user can control the portion of the document which is visible by

scrolling In computer displays, filmmaking, television production, and other kinetic displays, scrolling is sliding text, images or video across a monitor or display, vertically or horizontally. "Scrolling," as such, does not change the layout of the text ...

in the viewport.

References

{{Reflist

External links

* http://www.tecgraf.puc-rio.br/ftp_pub/lfm/L1J_WindowViewport.pdf * https://www.siggraph.org/education/materials/HyperGraph/viewing/view2d/2dview0.htm Computer graphics 3D computer graphics Computer graphics data structures

See also

References

External links