intro

glut(3GLUT)                          GLUT                          glut(3GLUT)



NAME
       glut - an introduction to the OpenGL Utility Toolkit

SYNOPSIS
       #include <GL/glut.h>

DESCRIPTION
       The OpenGL Utility Toolkit (GLUT) is a programming interface with ANSI
       C and FORTRAN bindings for writing window system independent OpenGL
       programs. The toolkit supports the following functionality:

              Multiple windows for OpenGL rendering.

              Callback driven event processing.

              Sophisticated input devices.

              An ``idle'' routine and timers.

              A simple, cascading pop-up menu facility.

              Utility routines to generate various solid and wire frame
              objects.

              Support for bitmap and stroke fonts.

              Miscellaneous window management functions, including managing
              overlays.

       An ANSI C implementation of GLUT for the X Window System has been
       implemented by the author. Windows NT and OS/2 versions of GLUT are
       also available.

BACKGROUND
       One of the major accomplishments in the specification of OpenGL was the
       isolation of window system dependencies from OpenGL's rendering model.
       The result is that OpenGL is window system independent.

       Window system operations such as the creation of a rendering window and
       the handling of window system events are left to the native window
       system to define. Necessary interactions between OpenGL and the window
       system such as creating and binding an OpenGL context to a window are
       described separately from the OpenGL specification in a window system
       dependent specification. For example, the GLX specification describes
       the standard by which OpenGL interacts with the X Window System.

       The predecessor to OpenGL is IRIS GL. Unlike OpenGL, IRIS GL does
       specify how rendering windows are created and manipulated. IRIS GL's
       windowing interface is reasonably popular largely because it is simple
       to use. IRIS GL programmers can worry about graphics programming
       without needing to be an expert in programming the native window
       system.  Experience also demonstrated that IRIS GL's windowing
       interface was high-level enough that it could be retargeted to
       different window systems.  Silicon Graphics migrated from NeWS to the X
       Window System without any major changes to IRIS GL's basic windowing
       interface.

       Removing window system operations from OpenGL is a sound decision
       because it allows the OpenGL graphics system to be retargeted to
       various systems including powerful but expensive graphics workstations
       as well as mass-production graphics systems like video games, set-top
       boxes for interactive television, and PCs.

       Unfortunately, the lack of a window system interface for OpenGL is a
       gap in OpenGL's utility. Learning native window system APIs such as the
       X Window System's Xlib or Motif can be daunting. Even those familiar
       with native window system APIs need to understand the interface that
       binds OpenGL to the native window system. And when an OpenGL program is
       written using the native window system interface, despite the
       portability of the program's OpenGL rendering code, the program itself
       will be window system dependent.

       Testing and documenting OpenGL's functionality lead to the development
       of the tk and aux toolkits. The aux toolkit is used in the examples
       found in the OpenGL Programming Guide. Unfortunately, aux has numerous
       limitations and its utility is largely limited to toy programs. The tk
       library has more functionality than aux but was developed in an ad hoc
       fashion and still lacks much important functionality that IRIS GL
       programmers expect, like pop-up menus and overlays.

       GLUT is designed to fill the need for a window system independent
       programming interface for OpenGL programs. The interface is designed to
       be simple yet still meet the needs of useful OpenGL programs. Features
       from the IRIS GL, aux, and tk interfaces are included to make it easy
       for programmers used to these interfaces to develop programs for GLUT.

PHILOSPHY
       GLUT simplifies the implementation of programs using OpenGL rendering.
       The GLUT application programming interface (API) requires very few
       routines to display a graphics scene rendered using OpenGL. The GLUT
       API (like the OpenGL API) is stateful. Most initial GLUT state is
       defined and the initial state is reasonable for simple programs.

       The GLUT routines also take relatively few parameters. No pointers are
       returned. The only pointers passed into GLUT are pointers to character
       strings (all strings passed to GLUT are copied, not referenced) and
       opaque font handles.

       The GLUT API is (as much as reasonable) window system independent. For
       this reason, GLUT does not return any native window system handles,
       pointers, or other data structures. More subtle window system
       dependencies such as reliance on window system dependent fonts are
       avoided by GLUT; instead, GLUT supplies its own (limited) set of fonts.

       For programming ease, GLUT provides a simple menu sub-API. While the
       menuing support is designed to be implemented as pop-up menus, GLUT
       gives window system leeway to support the menu functionality in another
       manner (pull-down menus for example).

       Two of the most important pieces of GLUT state are the current window
       and current menu. Most window and menu routines affect the current
       window or menu respectively. Most callbacks implicitly set the current
       window and menu to the appropriate window or menu responsible for the
       callback. GLUT is designed so that a program with only a single window
       and/or menu will not need to keep track of any window or menu
       identifiers.  This greatly simplifies very simple GLUT programs.

       GLUT is designed for simple to moderately complex programs focused on
       OpenGL rendering. GLUT implements its own event loop. For this reason,
       mixing GLUT with other APIs that demand their own event handling
       structure may be difficult. The advantage of a builtin event dispatch
       loop is simplicity.

       GLUT contains routines for rendering fonts and geometric objects,
       however GLUT makes no claims on the OpenGL display list name space. For
       this reason, none of the GLUT rendering routines use OpenGL display
       lists. It is up to the GLUT programmer to compile the output from GLUT
       rendering routines into display lists if this is desired.

       GLUT routines are logically organized into several sub-APIs according
       to their functionality. The sub-APIs are:

       Initialization.
              Command line processing, window system initialization, and
              initial window creation state are controlled by these routines.

       Beginning Event Processing.
              This routine enters GLUT's event processing loop. This routine
              never returns, and it continuously calls GLUT callbacks as
              necessary.

       Window Management.
              These routines create and control windows.

       Overlay Management.
              These routines establish and manage overlays for windows.

       Menu Management.
              These routines create and control pop-up menus.

       Callback Registration.
              These routines register callbacks to be called by the GLUT event
              processing loop.

       Color Index Colormap Management.
              These routines allow the manipulation of color index colormaps
              for windows.

       State Retrieval.
              These routines allows programs to retrieve state from GLUT.

       Font Rendering.
              These routines allow rendering of stroke and bitmap fonts.

       Geometric Shape Rendering.
              These routines allow the rendering of 3D geometric objects
              including spheres, cones, icosahedrons, and teapots.

CONVENTIONS
       GLUT window and screen coordinates are expressed in pixels. The upper
       left hand corner of the screen or a window is (0,0). X coordinates
       increase in a rightward direction; Y coordinates increase in a downward
       direction. Note: This is inconsistent with OpenGL's coordinate scheme
       that generally considers the lower left hand coordinate of a window to
       be at (0,0) but is consistent with most popular window systems.

       Integer identifiers in GLUT begin with one, not zero. So window
       identifiers, menu identifiers, and menu item indexes are based from
       one, not zero.

       In GLUT's ANSI C binding, for most routines, basic types (int, char*)
       are used as parameters. In routines where the parameters are directly
       passed to OpenGL routines, OpenGL types (GLfloat) are used.

       The header files for GLUT should be included in GLUT programs with the
       following include directive:

       #include <GL/glut.h>

       Because a very large window system software vendor (who will remain
       nameless) has an apparent inability to appreciate that OpenGL's API is
       independent of their window system API, portable ANSI C GLUT programs
       should not directly include <GL/gl.h> or <GL/glu.h>. Instead, ANSI C
       GLUT programs should rely on <GL/glut.h> to include the necessary
       OpenGL and GLU related header files.

       The ANSI C GLUT library archive is typically named libglut.a on Unix
       systems. GLUT programs need to link with the system's OpenGL and GLUT
       libraries (and any libraries these libraries potentially depend on). A
       set of window system dependent libraries may also be necessary for
       linking GLUT programs. For example, programs using the X11 GLUT
       implementation typically need to link with Xlib, the X extension
       library, possibly the X Input extension library, the X miscellaneous
       utilities library, and the math library. An example X11/Unix compile
       line would look like:

       cc -o foo foo.c -lglut -lGLU -lGL -lXmu -lXi -lXext -lX11 -lm

SEE ALSO
       glutAddMenuEntry, glutAddSubMenu, glutAttachMenu, glutBitmapCharacter,
       glutBitmapWidth, glutButtonBoxFunc, glutChangeToMenuEntry,
       glutChangeToSubMenu, glutCopyColormap, glutCreateMenu,
       glutCreateSubWindow, glutCreateWindow, glutDestroyMenu,
       glutDestroyWindow, glutDeviceGet, glutDialsFunc, glutDisplayFunc,
       glutEntryFunc, glutEstablishOverlay, glutExtensionSupported,
       glutFullScreen, glutGet, glutGetColor, glutGetModifiers, glutIdleFunc,
       glutInit, glutInitDisplayMode, glutInitWindowPosition,
       glutKeyboardFunc, glutLayerGet, glutMainLoop, glutMenuStatusFunc,
       glutMotionFunc, glutMouseFunc, glutOverlayDisplayFunc, glutPopWindow,
       glutPositionWindow, glutPostOverlayRedisplay, glutPostRedisplay,
       glutRemoveMenuItem, glutRemoveOverlay, glutReshapeFunc,
       glutReshapeWindow, glutSetColor, glutSetCursor, glutSetMenu,
       glutSetWindow, glutSetWindowTitle, glutShowOverlay, glutShowWindow,
       glutSolidCone, glutSolidCube, glutSolidDodecahedron,
       glutSolidIcosahedron, glutSolidOctahedron, glutSolidSphere,
       glutSolidTeapot, glutSolidTetrahedron, glutSolidTorus,
       glutSpaceballButtonFunc, glutSpaceballMotionFunc,
       glutSpaceballRotateFunc, glutSpecialFunc, glutStrokeCharacter,
       glutStrokeWidth, glutSwapBuffers, glutTabletButtonFunc,
       glutTabletMotionFunc, glutTimerFunc, glutUseLayer, glutVisibilityFunc,

REFERENCES
       Mark Kilgard, Programming OpenGL for the X Window System, Addison-
       Wesley, ISBN 0-201-48359-9, 1996.

       Mark Kilgard, The OpenGL Utility Toolkit (GLUT) Programming Interface
       API Version 3 (the official GLUT specification).

WEB REFERENCES
       Main GLUT page
       http://reality.sgi.com/mjk/glut3/glut3.html

       GLUT Frequently Asked Question list
       http://reality.sgi.com/mjk/glut3/glut-faq.html

       The OpenGL Utility Toolkit (GLUT) Programming Interface API Version 3
       http://reality.sgi.com/mjk/spec3/spec3.html
       http://reality.sgi.com/mjk/glut3/glut-3.spec.ps.gz

       OpenGL and X: An OpenGL Toolkit article (PostScript)
       http://reality.sgi.com/mjk/glut3/glut.column1.ps.gz

AUTHOR
       Mark J. Kilgard (mjk@nvidia.com)




GLUT                                  3.7                          glut(3GLUT)