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 sys-
tem 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 spec-
ify how rendering windows are created and manipulated. IRIS GL's win-
dowing 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. Expe-
rience 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 vari-
ous 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 portabil-
ity 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 pro-
grammers expect, like pop-up menus and overlays.
GLUT is designed to fill the need for a window system independent pro-
gramming 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 rou-
tines 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 dependen-
cies 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 win-
dow 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 identi-
fiers. 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 struc-
ture may be difficult. The advantage of a builtin event dispatch loop
is simplicity.
GLUT contains routines for rendering fonts and geometric objects, how-
ever 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 ini-
tial 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 nec-
essary.
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 identi-
fiers, 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 imple-
mentation 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(3), glutAddSubMenu(3), glutAttachMenu(3),
glutBitmapCharacter(3), glutBitmapWidth(3), glutButtonBoxFunc(3),
glutChangeToMenuEntry(3), glutChangeToSubMenu(3), glutCopyColormap(3),
glutCreateMenu(3), glutCreateSubWindow(3), glutCreateWindow(3),
glutDestroyMenu(3), glutDestroyWindow(3), glutDeviceGet(3),
glutDialsFunc(3), glutDisplayFunc(3), glutEntryFunc(3),
glutEstablishOverlay(3), glutExtensionSupported(3), glutFullScreen(3),
glutGet(3), glutGetColor(3), glutGetModifiers(3), glutIdleFunc(3),
glutInit(3), glutInitDisplayMode(3), glutInitWindowPosition(3),
glutKeyboardFunc(3), glutLayerGet(3), glutMainLoop(3),
glutMenuStatusFunc(3), glutMotionFunc(3), glutMouseFunc(3),
glutOverlayDisplayFunc(3), glutPopWindow(3), glutPositionWindow(3),
glutPostOverlayRedisplay(3), glutPostRedisplay(3), glutRemoveMenuItem(3),
glutRemoveOverlay(3), glutReshapeFunc(3), glutReshapeWindow(3),
glutSetColor(3), glutSetCursor(3), glutSetMenu(3), glutSetWindow(3),
glutSetWindowTitle(3), glutShowOverlay(3), glutShowWindow(3),
glutSolidCone(3), glutSolidCube(3), glutSolidDodecahedron(3),
glutSolidIcosahedron(3), glutSolidOctahedron(3), glutSolidSphere(3),
glutSolidTeapot(3), glutSolidTetrahedron(3), glutSolidTorus(3),
glutSpaceballButtonFunc(3), glutSpaceballMotionFunc(3),
glutSpaceballRotateFunc(3), glutSpecialFunc(3), glutStrokeCharacter(3),
glutStrokeWidth(3), glutSwapBuffers(3), glutTabletButtonFunc(3),
glutTabletMotionFunc(3), glutTimerFunc(3), glutUseLayer(3),
glutVisibilityFunc(3)
REFERENCES
Mark Kilgard, Programming OpenGL for the X Window System, Addison-Wes-
ley, 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://www.opengl.org/resources/libraries/glut/
GLUT Frequently Asked Question list
http://www.opengl.org/resources/libraries/glut/faq/
The OpenGL Utility Toolkit (GLUT) Programming Interface API Version 3
http://www.opengl.org/documentation/specs/glut/spec3/spec3.html
http://www.opengl.org/documentation/specs/glut/glut-3.spec.ps.gz
http://www.opengl.org/documentation/specs/glut/glut-3.spec.pdf
AUTHOR
Mark J. Kilgard (mjk@nvidia.com)
GLUT 3.7 glut(3GLUT)
Mac OS X 10.6 - Generated Thu Sep 17 20:20:37 CDT 2009