The OpenGL Utility Toolkit (GLUT) is a

library A library is a collection of materials, books or media that are accessible for use and not just for display purposes. A library provides physical (hard copies) or digital access (soft copies) materials, and may be a physical location or a vir ...

of utilities for

OpenGL OpenGL (Open Graphics Library) is a cross-language, cross-platform application programming interface (API) for rendering 2D and 3D vector graphics. The API is typically used to interact with a graphics processing unit (GPU), to achieve hardwa ...

programs, which primarily perform system-level I/O with the host

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...

. Functions performed include window definition, window control, and monitoring of

keyboard Keyboard may refer to: Text input * Keyboard, part of a typewriter * Computer keyboard ** Keyboard layout, the software control of computer keyboards and their mapping ** Keyboard technology, computer keyboard hardware and firmware Music * Musi ...

and

mouse A mouse ( : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...

input. Routines for drawing a number of geometric primitives (both in solid and wireframe mode) are also provided, including

cubes In geometry, a cube is a three-dimensional space, three-dimensional solid object bounded by six square (geometry), square faces, Facet (geometry), facets or sides, with three meeting at each vertex (geometry), vertex. Viewed from a corner it i ...

sphere A sphere () is a Geometry, geometrical object that is a solid geometry, three-dimensional analogue to a two-dimensional circle. A sphere is the Locus (mathematics), set of points that are all at the same distance from a given point in three ...

s and the

Utah teapot The Utah teapot, or the Newell teapot, is a 3D test model that has become a standard reference object and an in-joke within the computer graphics community. It is a mathematical model of an ordinary Melitta-brand teapot that appears solid w ...

. GLUT also has some limited support for creating pop-up menus. GLUT was written by Mark J. Kilgard, author of ''OpenGL Programming for the X Window System'' and ''The Cg Tutorial: The Definitive Guide to Programmable Real-Time Graphics'', while he was working for

Silicon Graphics Silicon Graphics, Inc. (stylized as SiliconGraphics before 1999, later rebranded SGI, historically known as Silicon Graphics Computer Systems or SGCS) was an American high-performance computing manufacturer, producing computer hardware and soft ...

Inc. The two aims of GLUT are to allow the creation of rather portable code between operating systems (GLUT is

cross-platform In computing, cross-platform software (also called multi-platform software, platform-agnostic software, or platform-independent software) is computer software that is designed to work in several computing platforms. Some cross-platform software r ...

) and to make learning OpenGL easier. Getting started with OpenGL programming while using GLUT often takes only a few lines of code and does not require knowledge of operating system–specific windowing APIs. All GLUT functions start with the glut prefix (for example, glutPostRedisplay marks the current window as needing to be redrawn).

Implementations

The original GLUT library by Mark Kilgard supports the

X Window System The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems. X provides the basic framework for a GUI environment: drawing and moving windows on the display device and interacting wit ...

(

GLX GLX (initialism for "OpenGL Extension to the X Window System") is an extension to the X Window System core protocol providing an interface between OpenGL and the X Window System as well as extensions to OpenGL itself. It enables programs wishing ...

) and was ported to

Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...

( WGL) by Nate Robins. Additionally,

macOS macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lapt ...

ships with a GLUT framework that supports its own NSGL/ CGL. Kilgard's GLUT library is no longer maintained, and its license did not permit the redistribution of modified versions of the library. This spurred the need for

free software Free software or libre software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versions. Free software is a matter of liberty, no ...

open source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...

reimplementations of the API from scratch. The first such library was

FreeGLUT FreeGLUT is an open-source alternative to the OpenGL Utility Toolkit (GLUT) library. GLUT (and hence FreeGLUT) allows the user to create and manage windows containing OpenGL contexts on a wide range of platforms and also read the mouse, keyboard ...

, which aims to be a reasonably close reproduction, though introducing a small number of new functions to deal with GLUT's limitations. OpenGLUT, a

fork In cutlery or kitchenware, a fork (from la, furca 'pitchfork') is a utensil, now usually made of metal, whose long handle terminates in a head that branches into several narrow and often slightly curved tines with which one can spear foods ei ...

of FreeGLUT, adds a number of new features to the original API, but work on it ceased in May 2005. Mark Kilgard has a GitHub repository for GLUT. The glut.h header file contains the following license: /* Copyright (c) Mark J. Kilgard, 1994, 1995, 1996, 1998, 2000, 2006, 2010. */ /* This program is freely distributable without licensing fees and is provided without guarantee or warrantee expressed or implied. This program is -not- in the public domain. */

Limitations

Some of GLUT's original design decisions made it hard for programmers to perform desired tasks. This led many to create non-canon patches and extensions to GLU

Some

reimplementations also include fixes. Some of the more notable limitations of the original GLUT library include: * The library requires programmers to call glutMainLoop(), a function which never returns. This makes it hard for programmers to integrate GLUT into a program or library which wishes to have control of its own event loop. A common patch to fix this is to introduce a new function, called glutCheckLoop() (macOS) or glutMainLoopEvent() (FreeGLUT/OpenGLUT), which runs only a single iteration of the GLUT event loop. Another common workaround is to run GLUT's event loop in a separate thread (computing), thread, although this may vary by operating system, and also may introduce

synchronization Synchronization is the coordination of events to operate a system in unison. For example, the conductor of an orchestra keeps the orchestra synchronized or ''in time''. Systems that operate with all parts in synchrony are said to be synchronou ...

issues or other problems: for example, the macOS GLUT implementation requires that glutMainLoop() be run in the main thread. * The fact that glutMainLoop() never returns also means that a GLUT program cannot exit the event loop.

fixes this by introducing a new function, glutLeaveMainLoop(). * The library terminates the process when the window is closed; for some applications this may not be desired. Thus, many implementations include an extra callback, such as glutWMCloseFunc(). Since it is no longer maintained (essentially replaced by the

) the above design issues are still not resolved in the original GLUT.

References

External links

GLUT - The OpenGL Utility Toolkit
{{Webarchive, url=https://web.archive.org/web/20180118221325/https://www.opengl.org/resources/libraries/glut/ , date=2018-01-18

(official documentation)
The OpenGL Utility Toolkit (GLUT) downloads
(source and pre-compiled libraries) OpenGL

Implementations

Limitations

See also

References

External links