The Open-Source

OpenGL Utility Toolkit

(freeglut)

Application Programming Interface

Version 4.0

The freeglut Programming Consortium

November, 2002


OpenGL is a trademark of Silicon Graphics, Inc. X Window System is a trademark of X Consortium, Inc.  Spaceball is a registered trademark of Spatial Systems Inc.
The authors have taken care in preparation of this documentation but make no expressed or implied warranty of any kind and assumes no responsibility for errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising from the use of information or programs contained herein.
 

1.0  Contents

1.0  Contents

2.0  Introduction

3.0  Background

3.1  Design Philosophy
3.2  Conventions
3.3  Terminology
3.4  Differences from GLUT 3.7


4.0  Initialization Functions

4.1  glutInit
4.2  glutInitWindowPosition, glutInitWindowSize
4.3  glutInitDisplayMode
4.4  glutInitDisplayString


5.0  Event Processing Functions

5.1  glutMainLoop
5.2  glutMainLoopEvent
5.3  glutLeaveMainLoop


6.0  Window Functions

6.1  glutCreateWindow
6.2  glutCreateSubwindow
6.3  glutDestroyWindow
6.4  glutSetWindow, glutGetWindow
6.5  glutSetWindowTitle, glutSetIconTitle
6.6  glutReshapeWindow
6.7  glutPositionWindow
6.8  glutShowWindow, glutHideWindow, glutIconifyWindow
6.9  glutPushWindow, glutPopWindow
6.10  glutFullScreen


7.0  Display Functions

7.1  glutPostRedisplay
7.2  glutPostWindowRedisplay
7.3  glutSwapBuffers


8.0  Mouse Cursor Functions

8.1  glutSetCursor
8.2  glutWarpPointer


9.0  Overlay Functions

9.1  glutEstablishOverlay
9.2  glutRemoveOverlay
9.3  glutUseLayer
9.4  glutPostOverlayRedisplay
9.5  glutPostWindowOverlayRedisplay
9.6  glutShowOverlay, glutHideOverlay


10.0  Menu Functions

10.1  glutCreateMenu
10.2  glutDestroyMenu
10.3  glutGetMenu, glutSetMenu
10.4  glutAddMenuEntry
10.5  glutAddSubMenu
10.6  glutChangeToMenuEntry
10.7  glutChangeToSubMenu
10.8  glutRemoveMenuItem
10.9  glutAttachMenu, glutDetachMenu


11.0  Global Callback Registration Functions

11.1  glutTimerFunc
11.2  glutIdleFunc


12.0  Window-Specific Callback Registration Functions

12.1  glutDisplayFunc
12.2  glutOverlayDisplayFunc
12.3  glutReshapeFunc
12.4  glutCloseFunc
12.5  glutKeyboardFunc
12.6  glutSpecialFunc
12.7  glutKeyboardUpFunc
12.8  glutSpecialUpFunc
12.9  glutMouseFunc
12.10  glutMotionFunc, glutPassiveMotionFunc
12.11  glutVisibilityFunc
12.12  glutEntryFunc
12.13  glutJoystickFunc
12.14  glutSpaceballMotionFunc
12.15  glutSpaceballRotateFunc
12.16  glutSpaceballButtonFunc
12.17  glutButtonBoxFunc
12.18  glutDialsFunc
12.19  glutTabletMotionFunc
12.20  glutTabletButtonFunc

12.21  glutMenuStatusFunc
12.22  glutWindowStatusFunc


13.0  State Setting and Retrieval Functions

13.1  glutSetOption
13.2  glutGet
13.3  glutDeviceGet
13.4  glutGetModifiers
13.5  glutLayerGet
13.6  glutExtensionSupported
13.7  glutGetProcAddress


14.0  Font Rendering Functions

14.1  glutBitmapCharacter
14.2  glutBitmapString
14.3  glutBitmapWidth
14.4  glutBitmapLength
14.5  glutBitmapHeight
14.6  glutStrokeCharacter
14.7  glutStrokeString
14.8  glutStrokeWidth
14.9  glutStrokeLength
14.10  glutStrokeHeight


15.0  Geometric Object Rendering Functions

15.1  glutWireSphere, glutSolidSphere
15.2  glutWireTorus, glutSolidTorus
15.3  glutWireCone, glutSolidCone
15.4  glutWireCube, glutSolidCube
15.5  glutWireTetrahedron, glutSolidTetrahedron
15.6  glutWireOctahedron, glutSolidOctahedron
15.7  glutWireDodecahedron, glutSolidDodecahedron
15.8  glutWireIcosahedron, glutSolidIcosahedron
15.9  glutWireRhombicDodecahedron, glutSolidRhombicDodecahedron
15.10  glutWireTeapot, glutSolidTeapot


16.0  Game Mode Functions

16.1  glutGameModeString
16.2  glutEnterGameMode, glutLeaveGameMode
16.3  glutGameModeGet


17.0  Video Resize Functions

17.1  glutVideoResizeGet
17.2  glutSetupVideoResizing, glutStopVideoResizing
17.3  glutVideoResize
17.4  glutVideoPan


18.0  Color Map Functions

18.1  glutSetColor, glutGetColor
18.2  glutCopyColormap


19.0  Miscellaneous Functions

19.1  glutIgnoreKeyRepeat, glutSetKeyRepeat
19.2  glutForceJoystickFunc
19.3  glutReportErrors


20.0  Usage Notes

21.0  Implementation Notes

22.0  GLUT State

23.0  "freeglut.h" Header File

24.0  References

25.0  Index
 
 

2.0  Introduction

 

3.0  Background

The OpenGL programming world owes a tremendous debt to Mr. Mark J. Kilgard for writing the OpenGL Utility Toolkit, or GLUT.  The GLUT library of functions allows an application programmer to create, control, and manipulate windows independent of what operating system the program is running on.  By hiding the dependency on the operating system from the application programmer, he allowed people to write truly portable OpenGL applications.

    Mr. Kilgard copyrighted his library and gave it a rather unusual license.  Under his license, people are allowed freely to copy and distribute the libraries and the source code, but they are not allowed to modify it.  For a long time this did not matter because the GLUT library worked so well and because Mr. Kilgard was releasing updates on a regular basis.  But with the passage of time, people started wanting some slightly different behaviours in their windowing system.  When Mr. Kilgard stopped supporting the GLUT library in 1999, having moved on to bigger and better things, this started to become a problem.

    In December 1999, Mr. Pawel Olzsta started work on an open-source clone of the GLUT library.  This open-source clone, which does not use any of the GLUT source code, has evolved into the present freeglut library.  This documentation specifies the application program interface to the freeglut library.

3.1  Design Philosophy

3.2  Conventions

3.3  Terminology

3.4  Differences from GLUT 3.7

Since the freeglut library was developed in order to update GLUT, it is natural that there will be some differences between the two.  Each function in the API notes any differences between the GLUT and the freeglut function behaviours.  The important ones are summarized here.

3.4.1  glutMainLoop Behaviour

One of the commonest complaints about the GLUT library was that once an application called "glutMainLoop", it never got control back.  There was no way for an application to loop in GLUT for a while, possibly as a subloop while a specific window was open, and then return to the calling function.  A new function, "glutMainLoopEvent", has been added to allow this functionality.  Another function, "glutLeaveMainLoop ", has also been added to allow the application to tell freeglut to clean up and close down.

3.4.2  Action on Window Closure

Another difficulty with GLUT, especially with multiple-window programs, is that if the user clicks on the "x" in the window header the application exits immediately.  The application programmer can now set an option, " GLUT_ACTION_ON_WINDOW_CLOSE", to specify whether execution should continue, whether GLUT should return control to the main program, or whether GLUT should simply exit (the default).

3.4.3  Changes to Callbacks

Several new callbacks have been added and several callbacks which were specific to Silicon Graphics hardware have not been implemented.  Most or all of the new callbacks are listed in the GLUT Version 4 "glut.h" header file but did not make it into the documentation.  The new callbacks consist of regular and special key release callbacks, a joystick callback, a menu state callback (with one argument, distinct from the menu status callback which has three arguments), and a window status callback
(also with one argument).  Unsupported callbacks are the three Spaceball callbacks, the ButtonBox callback, the Dials callback, and the two Tablet callbacks.  If the user has a need for an unsupported callback he should contact the freeglut development team.

3.4.4  String Rendering

New functions have been added to render full character strings (including carriage returns) rather than rendering one character at a time.  More functions return the widths of character strings and the font heights, in pixels for bitmapped fonts and in OpenGL units for the stroke fonts.

3.4.5  Geometry Rendering

Two functions have been added to render a wireframe and a solid rhombic dodecahedron.

3.4.5  Extension Function Queries

glutGetProcAddress is a wrapper for the glXGetProcAddressARB and wglGetProcAddress functions.

4.0  Initialization Functions

4.1  glutInit

4.2  glutInitWindowPosition, glutInitWindowSize

The "glutInitWindowPosition " and "glutInitWindowSize " functions specify a desired position and size for windows that freeglut will create in the future.

Usage

void glutInitWindowPosition ( int x, int y ) ;
void glutInitWindowSize ( int width, int height ) ;

Description

The "glutInitWindowPosition " and "glutInitWindowSize" functions specify a desired position and size for windows that freeglut will create in the future.  The position is measured in pixels from the upper left hand corner of the screen, with "x" increasing to the right and "y" increasing towards the bottom of the screen.  The size is measured in pixels.  Freeglut does not promise to follow these specifications in creating its windows, it certainly makes an attempt to.

The position and size of a window are a matter of some subtlety.  Most windows have a usable area surrounded by a border and with a title bar on the top.  The border and title bar are commonly called "decorations."  The position of the window unfortunately varies with the operating system.  On Linux, it is the coordinates of the upper left-hand corner of its decorations.  On Windows, it is the coordinates of the upper left hand corner of its usable interior.  For both operating systems, the size of the window is the size of the usable interior.

Windows has some additional quirks which the application programmer should know about.  First, the minimum y-coordinate of a window decoration is zero.  (This is a feature of freeglut and can be adjusted if so desired.)  Second, there appears to be a minimum window width on Windows which is 104 pixels.  The user may specify a smaller width, but the Windows system calls ignore it.  It is also impossible to make a window narrower than this by dragging on its corner.

Changes From GLUT

For some reason, GLUT is not affected by the 104-pixel minimum window width.  If the user clicks on the corner of a window which is narrower than this amount, the window will immediately snap out to this width, but the application can call "glutReshapeWindow " and make a window narrower again.

4.3  glutInitDisplayMode

4.4  glutInitDisplayString

5.0  Event Processing Functions

After an application has finished initializing its windows and menus, it enters an event loop.  Within this loop, freeglut polls the data entry devices (keyboard, mouse, etc.) and calls the application's appropriate callbacks.

In GLUT, control never returned from the event loop (as invoked by the "glutMainLoop" function) to the calling function.  This prevented an application from having re-entrant code, in which GLUT could be invoked from within a callback, and it prevented the application from doing any post-processing (such as freeing allocated memory) after GLUT had closed down.  Freeglut allows the application programmer to specify more direct control over the event loop by means of two new functions.  The first, "glutMainLoopEvent", processes a single iteration of the event loop and allows the application to use a different event loop controller or to contain re-entrant code.  The second, " glutLeaveMainLoop", causes the event loop to exit nicely; this is preferable to the application's calling "exit" from within a GLUT callback.

5.1  glutMainLoop

The "glutMainLoop" function enters the event loop.

Usage

void glutMainLoop ( void ) ;

Description

The  "glutMainLoop" function causes the program to enter the window event loop.  An application should call this function at most once.  It will call any application callback functions as required to process mouse clicks, mouse motion, key presses, and so on.

Changes From GLUT

In GLUT, there was absolutely no way for the application programmer to have control return from the "glutMainLoop " function to the calling function.  Freeglut allows the programmer to force this by setting the "GLUT_ACTION_ON_WINDOW_CLOSE" option and invoking the "glutLeaveMainLoop" function from one of the callbacks.  Stopping the program this way is preferable to simply calling "exit " from within a callback because this allows freeglut to free allocated memory and otherwise clean up after itself.  (I know I just said this, but I think it is important enough that it bears repeating.)

5.2  glutMainLoopEvent

The "glutMainLoopEvent" function processes a single iteration in the freeglut event loop.

Usage

void glutMainLoopEvent ( void ) ;

Description

The  "glutMainLoopEvent " function causes freeglut to process one iteration's worth of events in its event loop.  This allows the application to control its own event loop and still use the freeglut windowing system.

Changes From GLUT

GLUT does not include this function.

5.3  glutLeaveMainLoop

The "glutLeaveMainLoop" function causes freeglut to stop its event loop.

Usage

void glutLeaveMainLoop ( void ) ;

Description

The  "glutLeaveMainLoop " function causes freeglut to stop the event loop.  If the " GLUT_ACTION_ON_WINDOW_CLOSE" option has been set to "GLUT_ACTION_CONTINUE_EXECUTION ", control will return to the function which called "glutMainLoop "; otherwise the application will exit.

If the application has two nested calls to "glutMainLoop" and calls "glutLeaveMainLoop", the behaviour of freeglut is undefined.  It may leave only the inner nested loop or it may leave both loops.  If the reader has a strong preference for one behaviour over the other he should contact the freeglut Programming Consortium and ask for the code to be fixed.

Changes From GLUT

GLUT does not include this function.

6.0  Window Functions

6.1  glutCreateWindow

6.2  glutCreateSubwindow

6.3  glutDestroyWindow

6.4  glutSetWindow, glutGetWindow

6.5  glutSetWindowTitle, glutSetIconTitle

6.6  glutReshapeWindow

6.7  glutPositionWindow

6.8  glutShowWindow, glutHideWindow, glutIconifyWindow

6.9  glutPushWindow, glutPopWindow

6.10  glutFullScreen

7.0  Display Functions

7.1  glutPostRedisplay

7.2  glutPostWindowRedisplay

7.3  glutSwapBuffers

8.0  Mouse Cursor Functions

8.1  glutSetCursor

8.2  glutWarpPointer

9.0  Overlay Functions

Freeglut does not allow overlays, although it does "answer the mail" with function stubs so that GLUT-based programs can compile and link against freeglut without modification.  If the reader needs overlays, he should contact the freeglut Programming Consortium and ask for them to be implemented.  He should also be prepared to assist in the implementation.

9.1  glutEstablishOverlay

The "glutEstablishOverlay" function is not implemented in freeglut .

Usage

void glutEstablishOverlay ( void ) ;

Description

The "glutEstablishOverlay" function is not implemented in freeglut.

Changes From GLUT

GLUT implements this function.

9.2  glutRemoveOverlay

The "glutRemoveOverlay" function is not implemented in freeglut .

Usage

void glutRemoveOverlay ( void ) ;

Description

The "glutRemoveOverlay" function is not implemented in freeglut.

Changes From GLUT

GLUT implements this function.

9.3  glutUseLayer

The "glutUseLayer" function is not implemented in freeglut .

Usage

void glutUseLayer (  GLenum layer ) ;

Description

The "glutUseLayer" function is not implemented in freeglut.

Changes From GLUT

GLUT implements this function.

9.4  glutPostOverlayRedisplay

The "glutPostOverlayRedisplay " function is not implemented in freeglut.

Usage

void glutPostOverlayRedisplay ( void ) ;

Description

The "glutPostOverlayRedisplay " function is not implemented in freeglut.

Changes From GLUT

GLUT implements this function.

9.5  glutPostWindowOverlayRedisplay

The "glutPostWindowOverlayRedisplay " function is not implemented in freeglut.

Usage

void glutPostWindowOverlayRedisplay ( int window ) ;

Description

The "glutPostWindowOverlayRedisplay " function is not implemented in freeglut.

Changes From GLUT

GLUT implements this function.

9.6  glutShowOverlay, glutHideOverlay

The "glutShowOverlay" and "glutHideOverlay" functions are not implemented in freeglut .

Usage

void glutShowOverlay( void ) ;
void glutHideOverlay( void ) ;

Description

The "glutShowOverlay" and " glutHideOverlay" functions are not implemented in freeglut .

Changes From GLUT

GLUT implements these functions.

10.0  Menu Functions

10.1  glutCreateMenu

10.2  glutDestroyMenu

10.3  glutGetMenu, glutSetMenu

10.4  glutAddMenuEntry

10.5  glutAddSubMenu

10.6  glutChangeToMenuEntry

10.7  glutChangeToSubMenu

10.8  glutRemoveMenuItem

10.9  glutAttachMenu, glutDetachMenu

11.0  Global Callback Registration Functions

11.1  glutTimerFunc

11.2  glutIdleFunc

The "glutIdleFunc" function sets the global idle callback. Freeglut calls the idle callback when there are no inputs from the user.

Usage

void glutIdleFunc ( void (*func) ( void ) ) ;

func    The new global idle callback function

Description

The  "glutIdleFunc" function specifies the function that freeglut will call to perform background processing tasks such as continuous animation when window system events are not being received.  If enabled, this function is called continuously from freeglut while no events are received.  The callback function has no parameters and returns no value.  Freeglut does not change the current window or the current menu before invoking the idle callback; programs with multiple windows or menus must explicitly set the current window and current menu and not rely on its current setting.
    The amount of computation and rendering done in an idle callback should be minimized to avoid affecting the program's interactive response.  In general, no more than a single frame of rendering should be done in a single invocation of an idle callback.
    Calling "glutIdleFunc" with a NULL argument disables the call to an idle callback.

Changes From GLUT

Application programmers should note that if they have specified the "continue execution" action on window closure, freeglut will continue to call the idle callback after the user has closed a window by clicking on the "x" in the window header bar.  If the idle callback renders a particular window (this is considered bad form but is frequently done anyway), the programmer should supply a window closure callback for that window which changes or disables the idle callback.

12.0  Window-Specific Callback Registration Functions

12.1  glutDisplayFunc

12.2  glutOverlayDisplayFunc

12.3  glutReshapeFunc

12.4  glutCloseFunc

12.5  glutKeyboardFunc

12.6  glutSpecialFunc

The "glutSpecialFunc" function sets the window's special key press callback. Freeglut calls the special key press callback when the user presses a special key.

Usage

void glutSpecialFunc ( void (*func) ( int key, int x, int y ) ) ;

func    The window's new special key press callback function
key     The key whose press triggers the callback
x       The x-coordinate of the mouse relative to the window at the time the key is pressed
y       The y-coordinate of the mouse relative to the window at the time the key is pressed

Description

The  "glutSpecialFunc" function specifies the function that freeglut will call when the user presses a special key on the keyboard.  The callback function has one argument:  the name of the function to be invoked ("called back") at the time at which the special key is pressed.  The function returns no value.  Freeglut sets the current window to the window which is active when the callback is invoked.  "Special keys" are the function keys, the arrow keys, the Page Up and Page Down keys, and the Insert key.  The Delete key is considered to be a regular key.
    Calling "glutSpecialUpFunc" with a NULL argument disables the call to the window's special key press callback.

    The "key " argument may take one of the following defined constant values:

Changes From GLUT

None.

12.7  glutKeyboardUpFunc

The "glutKeyboardUpFunc" function sets the window's key release callback. Freeglut calls the key release callback when the user releases a key.

Usage

void glutKeyboardUpFunc ( void (*func) ( unsigned char key, int x, int y ) ) ;

func    The window's new key release callback function
key     The key whose release triggers the callback
x       The x-coordinate of the mouse relative to the window at the time the key is released
y       The y-coordinate of the mouse relative to the window at the time the key is released

Description

The  "glutKeyboardUpFunc " function specifies the function that freeglut will call when the user releases a key from the keyboard.  The callback function has one argument:  the name of the function to be invoked ("called back") at the time at which the key is released.  The function returns no value.  Freeglut sets the current window to the window which is active when the callback is invoked.
    While freeglut checks for upper or lower case letters, it does not do so for non-alphabetical characters.  Nor does it account for the Caps-Lock key being on.  The operating system may send some unexpected characters to freeglut, such as "8" when the user is pressing the Shift key.  Freeglut also invokes the callback when the user releases the Control, Alt, or Shift keys, among others.  Releasing the Delete key causes this function to be invoked with a value of 127 for "key".
    Calling "glutKeyboardUpFunc" with a NULL argument disables the call to the window's key release callback.

Changes From GLUT

This function is not implemented in GLUT versions before Version 4.  It has been designed to be as close to GLUT as possible.  Users who find differences should contact the freeglut Programming Consortium to have them fixed.

12.8  glutSpecialUpFunc

The "glutSpecialUpFunc" function sets the window's special key release callback. Freeglut calls the special key release callback when the user releases a special key.

Usage

void glutSpecialUpFunc ( void (*func) ( int key, int x, int y ) ) ;

func    The window's new special key release callback function
key     The key whose release triggers the callback
x       The x-coordinate of the mouse relative to the window at the time the key is released
y       The y-coordinate of the mouse relative to the window at the time the key is released

Description

The  "glutSpecialUpFunc " function specifies the function that freeglut will call when the user releases a special key from the keyboard.  The callback function has one argument:  the name of the function to be invoked ("called back") at the time at which the special key is released.  The function returns no value.  Freeglut sets the current window to the window which is active when the callback is invoked.  "Special keys" are the function keys, the arrow keys, the Page Up and Page Down keys, and the Insert key.  The Delete key is considered to be a regular key.
    Calling "glutSpecialUpFunc" with a NULL argument disables the call to the window's special key release callback.

    The "key " argument may take one of the following defined constant values:

Changes From GLUT

This function is not implemented in GLUT versions before Version 4.  It has been designed to be as close to GLUT as possible.  Users who find differences should contact the freeglut Programming Consortium to have them fixed.

12.9  glutMouseFunc

12.10  glutMotionFunc, glutPassiveMotionFunc

12.11  glutVisibilityFunc

12.12  glutEntryFunc

12.13  glutJoystickFunc

12.14  glutSpaceballMotionFunc

The "glutSpaceballMotionFunc" function is not implemented in freeglut, although the library does "answer the mail" to the extent that a call to the function will not produce an error..

Usage

void glutSpaceballMotionFunc ( void (* callback)( int x, int y, int z ) ) ;

Description

The "glutSpaceballMotionFunc " function is not implemented in freeglut.

Changes From GLUT

GLUT implements this function.

12.15  glutSpaceballRotateFunc

The "glutSpaceballRotateFunc" function is not implemented in freeglut, although the library does "answer the mail" to the extent that a call to the function will not produce an error..

Usage

void glutSpaceballRotateFunc ( void (* callback)( int x, int y, int z ) ) ;

Description

The "glutSpaceballRotateFunc " function is not implemented in freeglut.

Changes From GLUT

GLUT implements this function.

12.16  glutSpaceballButtonFunc

The "glutSpaceballButtonFunc" function is not implemented in freeglut, although the library does "answer the mail" to the extent that a call to the function will not produce an error..

Usage

void glutSpaceballButtonFunc ( void (* callback)( int button, int updown ) ) ;

Description

The "glutSpaceballButtonFunc " function is not implemented in freeglut.

Changes From GLUT

GLUT implements this function.

12.17  glutButtonBoxFunc

The "glutSpaceballButtonBoxFunc" function is not implemented in freeglut, although the library does "answer the mail" to the extent that a call to the function will not produce an error..

Usage

void glutSpaceballButtonBoxFunc ( void (* callback)( int button, int updown ) ) ;

Description

The "glutSpaceballButtonBoxFunc " function is not implemented in freeglut.

Changes From GLUT

GLUT implements this function.

12.18  glutDialsFunc

The "glutDialsFunc" function is not implemented in freeglut , although the library does "answer the mail" to the extent that a call to the function will not produce an error..

Usage

void glutDialsFunc ( void (* callback)( int dial, int value ) ) ;

Description

The "glutDialsFunc" function is not implemented in freeglut.

Changes From GLUT

GLUT implements this function.

12.19  glutTabletMotionFunc

The "glutTabletMotionFunc" function is not implemented in freeglut, although the library does "answer the mail" to the extent that a call to the function will not produce an error..

Usage

void glutTabletMotionFunc ( void (* callback)( int x, int y ) ) ;

Description

The "glutTabletMotionFunc" function is not implemented in freeglut.

Changes From GLUT

GLUT implements this function.

12.20  glutTabletButtonFunc

The "glutTabletButtonFunc" function is not implemented in freeglut, although the library does "answer the mail" to the extent that a call to the function will not produce an error..

Usage

void glutTabletButtonFunc ( void (* callback)( int button, int updown, int x, int y ) ) ;

Description

The "glutTabletButtonFunc" function is not implemented in freeglut.

Changes From GLUT

GLUT implements this function.

12.21  glutMenuStatusFunc

12.22  glutWindowStatusFunc

13.0  State Setting and Retrieval Functions

13.1  glutSetOption

13.2  glutGet

13.3  glutDeviceGet

13.4  glutGetModifiers

13.5  glutLayerGet

13.6  glutExtensionSupported

13.7  glutGetProcAddress

glutGetProcAddress returns a pointer to a named GL or FreeGLUT function.

Usage

void *glutGetProcAddress ( const char *procName ) ;

procName        Name of an OpenGL or GLUT function.

Description

glutGetProcAddress is useful for dealing with OpenGL extensions. If an application calls OpenGL extension functions directly, that application will only link/run with an OpenGL library that supports the extension. By using a function pointer returned from glutGetProcAddress(), the application will avoid this hard dependency and be more portable and interoperate better with various implementations of OpenGL.

Both OpenGL functions and FreeGLUT functions can be queried with this function.

NOTE: this function is not supported in GLUT.

14.0  Font Rendering Functions

Freeglut supports two types of font rendering:  bitmap fonts, which are rendered using the "glBitmap" function call, and stroke fonts, which are rendered as sequences of OpenGL line segments.  Because they are rendered as bitmaps, the bitmap fonts tend to render more quickly than stroke fonts, but they are less flexible in terms of scaling and rendering.  Bitmap font characters are positioned with calls to the "glRasterPos* " functions while stroke font characters use the OpenGL transformations to position characters.

    It should be noted that freeglut fonts are similar but not identical to GLUT fonts.  At the moment, freeglut fonts do not support the "`" (backquote) and "|" (vertical line) characters; in their place it renders asterisks.

    Freeglut supports the following bitmap fonts:

Freeglut calls "glRasterPos4v" to advance the cursor by the width of a character and to render carriage returns when appropriate.  It does not use any display lists in it rendering in bitmap fonts.

    Freeglut supports the following stroke fonts:

Freeglut does not use any display lists in its rendering of stroke fonts.  It calls "glTranslatef" to advance the cursor by the width of a character and to render carriage returns when appropriate.

14.1  glutBitmapCharacter

The "glutBitmapCharacter" function renders a single bitmapped character in the current window using the specified font.

Usage

void glutBitmapCharacter ( void *font, int character ) ;

font        The bitmapped font to use in rendering the character
character   The ASCII code of the character to be rendered

Description

The  "glutBitmapCharacter " function renders the given character in the specified bitmap font.  Freeglut automatically sets the necessary pixel unpack storage modes and restores the existing modes when it has finished.  Before the first call to "glutBitMapCharacter " the application program should call "glRasterPos*" to set the position of the character in the window.  The "glutBitmapCharacter " function advances the cursor position as part of its call to "glBitmap " and so the application does not need to call "glRasterPos*" again for successive characters on the same line.

Changes From GLUT

Nonexistent characters are rendered as asterisks.  The rendering position in freeglut is apparently off from GLUT's position by a few pixels vertically and one or two pixels horizontally.

14.2  glutBitmapString

The "glutBitmapString" function renders a string of bitmapped characters in the current window using the specified font.

Usage

void glutBitmapString ( void *font, char *string ) ;

font      The bitmapped font to use in rendering the character string
string    String of characters to be rendered

Description

The  "glutBitmapString " function renders the given character string in the specified bitmap font.  Freeglut automatically sets the necessary pixel unpack storage modes and restores the existing modes when it has finished.  Before calling "glutBitMapString" the application program should call "glRasterPos*" to set the position of the string in the window.  The "glutBitmapString" function handles carriage returns.  Nonexistent characters are rendered as asterisks.

Changes From GLUT

GLUT does not include this function.

14.3  glutBitmapWidth

The "glutBitmapWidth" function returns the width in pixels of a single bitmapped character in the specified font.

Usage

int glutBitmapWidth ( void *font, int character ) ;

font        The bitmapped font to use in calculating the character width
character   The ASCII code of the character

Description

The  "glutBitmapWidth" function returns the width of the given character in the specified bitmap font.  Because the font is bitmapped, the width is an exact integer.

Changes From GLUT

Nonexistent characters return the width of an asterisk.

14.4  glutBitmapLength

The "glutBitmapLength" function returns the width in pixels of a string of bitmapped characters in the specified font.

Usage

int glutBitmapLength ( void *font, char *string ) ;

font    The bitmapped font to use in calculating the character width
string  String of characters whose width is to be calculated

Description

The  "glutBitmapLength " function returns the width in pixels of the given character string in the specified bitmap font.  Because the font is bitmapped, the width is an exact integer:  the return value is identical to the sum of the character widths returned by a series of calls to "glutBitmapWidth ".  The width of nonexistent characters is counted to be the width of an asterisk.

    If the string contains one or more carriage returns, freeglut calculates the widths in pixels of the lines separately and returns the largest width.

Changes From GLUT

GLUT does not include this function.

14.5  glutBitmapHeight

The "glutBitmapHeight" function returns the height in pixels of the specified font.

Usage

int glutBitmapHeight ( void *font ) ;

font        The bitmapped font to use in calculating the character height

Description

The  "glutBitmapHeight " function returns the height of a character in the specified bitmap font.  Because the font is bitmapped, the height is an exact integer.  The fonts are designed such that all characters have (nominally) the same height.

Changes From GLUT

GLUT does not include this function.

14.6  glutStrokeCharacter

The "glutStrokeCharacter" function renders a single stroke character in the current window using the specified font.

Usage

void glutStrokeCharacter ( void *font, int character ) ;

font        The stroke font to use in rendering the character
character   The ASCII code of the character to be rendered

Description

The  "glutStrokeCharacter " function renders the given character in the specified stroke font.  Before the first call to "glutStrokeCharacter" the application program should call the OpenGL transformation (positioning and scaling) functions to set the position of the character in the window.  The "glutStrokeCharacter " function advances the cursor position by a call to "glTranslatef " and so the application does not need to call the OpenGL positioning functions again for successive characters on the same line.

Changes From GLUT

Nonexistent characters are rendered as asterisks.

14.7  glutStrokeString

The "glutStrokeString" function renders a string of characters in the current window using the specified stroke font.

Usage

void glutStrokeString ( void *font, char *string ) ;

font      The stroke font to use in rendering the character string
string    String of characters to be rendered

Description

The  "glutStrokeString " function renders the given character string in the specified stroke font.  Before calling "glutStrokeString" the application program should call the OpenGL transformation (positioning and scaling) functions to set the position of the string in the window.  The "glutStrokeString " function handles carriage returns.  Nonexistent characters are rendered as asterisks.

Changes From GLUT

GLUT does not include this function.

14.8  glutStrokeWidth

The "glutStrokeWidth" function returns the width in pixels of a single character in the specified stroke font.

Usage

int glutStrokeWidth ( void *font, int character ) ;

font        The stroke font to use in calculating the character width
character   The ASCII code of the character

Description

The  "glutStrokeWidth" function returns the width of the given character in the specified stroke font.  Because the font is a stroke font, the width is actually a floating-point number; the function rounds it to the nearest integer for the return value.

Changes From GLUT

Nonexistent characters return the width of an asterisk.

14.9  glutStrokeLength

The "glutStrokeLength" function returns the width in pixels of a string of characters in the specified stroke font.

Usage

int glutStrokeLength ( void *font, char *string ) ;

font    The stroke font to use in calculating the character width
string  String of characters whose width is to be calculated

Description

The  "glutStrokeLength " function returns the width in pixels of the given character string in the specified stroke font.  Because the font is a stroke font, the width of an individual character is a floating-point number.  Freeglut adds the floating-point widths and rounds the funal result to return the integer value.  Thus the return value may differ from the sum of the character widths returned by a series of calls to "glutStrokeWidth ".  The width of nonexistent characters is counted to be the width of an asterisk.

    If the string contains one or more carriage returns, freeglut calculates the widths in pixels of the lines separately and returns the largest width.

Changes From GLUT

GLUT does not include this function.

14.10  glutStrokeHeight

The "glutStrokeHeight" function returns the height in pixels of the specified font.

Usage

GLfloat glutStrokeHeight ( void *font ) ;

font        The stroke font to use in calculating the character height

Description

The  "glutStrokeHeight " function returns the height of a character in the specified stroke font.  The application programmer should note that, unlike the other freeglut font functions, this one returns a floating-point number.  The fonts are designed such that all characters have (nominally) the same height.

Changes From GLUT

GLUT does not include this function.

15.0  Geometric Object Rendering Functions

Freeglut includes eighteen routines for generating easily-recognizable 3-d geometric objects.  These routines are effectively the same ones that are included in the GLUT library, and reflect the functionality available in the aux toolkit described in the OpenGL Programmer's Guide .  They are included to allow programmers to create with a single line of code a three-dimensional object which can be used to test a variety of OpenGL functionality.  None of the routines generates a display list for the object which it draws.  The functions generate normals appropriate for lighting but, except for the teapon functions, do not generate texture coordinates.

15.1  glutWireSphere, glutSolidSphere

The "glutWireSphere" and "glutSolidSphere" functions draw a wireframe and solid sphere respectively.

Usage

void glutWireSphere ( GLdouble dRadius, GLint slices, GLint stacks ) ;

void glutSolidSphere ( GLdouble dRadius, GLint slices, GLint stacks ) ;

dRadius       The desired radius of the sphere

slices        The desired number of slices (divisions in the longitudinal direction) in the sphere

stacks        The desired number of stacks (divisions in the latitudinal direction) in the sphere.  The number of points in this direction, including the north and south poles, is stacks+1

Description

The "glutWireSphere" and " glutSolidSphere" functions render a sphere centered at the origin of the modeling coordinate system.  The north and south poles of the sphere are on the positive and negative Z-axes respectively and the prime meridian crosses the positive X-axis.

Changes From GLUT

None that we know of.

15.2  glutWireTorus, glutSolidTorus

The "glutWireTorus" and "glutSolidTorus" functions draw a wireframe and solid torus (donut shape) respectively.

Usage

void glutWireTorus ( GLdouble dInnerRadius, GLdouble dOuterRadius, GLint nSides, GLint nRings ) ;

void glutSolidTorus ( GLdouble dInnerRadius, GLdouble dOuterRadius, GLint nSides, GLint nRings ) ;

dInnerRadius        The desired inner radius of the torus, from the origin to the circle defining the centers of the outer circles

dOuterRadius        The desired outer radius of the torus, from the center of the outer circle to the actual surface of the torus

nSides        The desired number of segments in a single outer circle of the torus

nRings        The desired number of outer circles around the origin of the torus

Description

The "glutWireTorus" and " glutSolidTorus" functions render a torus centered at the origin of the modeling coordinate system.  The torus is circularly symmetric about the Z-axis and starts at the positive X-axis.

Changes From GLUT

None that we know of.

15.3  glutWireCone, glutSolidCone

The "glutWireCone" and "glutSolidCone" functions draw a wireframe and solid cone respectively.

Usage

void glutWireCone ( GLdouble base, GLdouble height, GLint slices, GLint stacks ) ;

void glutSolidCone ( GLdouble base, GLdouble height, GLint slices, GLint stacks ) ;

base          The desired radius of the base of the cone

height        The desired height of the cone

slices        The desired number of slices around the base of the cone

stacks        The desired number of segments between the base and the tip of the cone (the number of points, including the tip, is stacks + 1)

Description

The "glutWireCone" and " glutSolidCone" functions render a right circular cone with a base centered at the origin and in the X-Y plane and its tip on the positive Z-axis.  The wire cone is rendered with triangular elements.

Changes From GLUT

None that we know of.

15.4  glutWireCube, glutSolidCube

The "glutWireCube" and "glutSolidCube" functions draw a wireframe and solid cube respectively.

Usage

void glutWireCube ( GLdouble dSize ) ;

void glutSolidCube ( GLdouble dSize ) ;

dSize         The desired length of an edge of the cube

Description

The "glutWireCube" and " glutSolidCube" functions render a cube of the desired size, centered at the origin.  Its faces are normal to the coordinate directions.

Changes From GLUT

None that we know of.

15.5  glutWireTetrahedron, glutSolidTetrahedron

The "glutWireTetrahedron" and "glutSolidTetrahedron" functions draw a wireframe and solid tetrahedron (four-sided Platonic solid) respectively.

Usage

void glutWireTetrahedron ( void ) ;

void glutSolidTetrahedron ( void ) ;

Description

The "glutWireTetrahedron" and "glutSolidTetrahedron" functions render a tetrahedron whose corners are each a distance of one from the origin.  The length of each side is 2/3 sqrt(6).  One corner is on the positive X-axis and another is in the X-Y plane with a positive Y-coordinate.

Changes From GLUT

None that we know of.

15.6  glutWireOctahedron, glutSolidOctahedron

The "glutWireOctahedron" and "glutSolidOctahedron" functions draw a wireframe and solid octahedron (eight-sided Platonic solid) respectively.

Usage

void glutWireOctahedron ( void ) ;

void glutSolidOctahedron ( void ) ;

Description

The "glutWireOctahedron" and "glutSolidOctahedron" functions render an octahedron whose corners are each a distance of one from the origin.  The length of each side is sqrt(2).  The corners are on the positive and negative coordinate axes.

Changes From GLUT

None that we know of.

15.7  glutWireDodecahedron, glutSolidDodecahedron

The "glutWireDodecahedron" and "glutSolidDodecahedron " functions draw a wireframe and solid dodecahedron (twelve-sided Platonic solid) respectively.

Usage

void glutWireDodecahedron ( void ) ;

void glutSolidDodecahedron ( void ) ;

Description

The "glutWireDodecahedron" and "glutSolidDodecahedron" functions render a dodecahedron whose corners are each a distance of sqrt(3) from the origin.  The length of each side is sqrt(5)-1.  There are twenty corners; interestingly enough, eight of them coincide with the corners of a cube with sizes of length 2.

Changes From GLUT

None that we know of.

15.8  glutWireIcosahedron, glutSolidIcosahedron

The "glutWireIcosahedron" and "glutSolidIcosahedron" functions draw a wireframe and solid icosahedron (twenty-sided Platonic solid) respectively.

Usage

void glutWireIcosahedron ( void ) ;

void glutSolidIcosahedron ( void ) ;

Description

The "glutWireIcosahedron" and "glutSolidIcosahedron" functions render an icosahedron whose corners are each a unit distance from the origin.  The length of each side is slightly greater than one.  Two of the corners lie on the positive and negative X-axes.

Changes From GLUT

None that we know of.

15.7  glutWireRhombicDodecahedron, glutSolidRhombicDodecahedron

The "glutWireRhombicDodecahedron" and "glutSolidRhombicDodecahedron " functions draw a wireframe and solid rhombic dodecahedron (twelve-sided semi-regular solid) respectively.

Usage

void glutWireRhombicDodecahedron ( void ) ;

void glutSolidRhombicDodecahedron ( void ) ;

Description

The "glutWireRhombicDodecahedron " and "glutSolidRhombicDodecahedron" functions render a rhombic dodecahedron whose corners are at most a distance of one from the origin.  The rhombic dodecahedron has faces which are identical rhombuses (rhombi?) but which have some vertices at which three faces meet and some vertices at which four faces meet.  The length of each side is sqrt(3)/2.  Vertices at which four faces meet are found at (0, 0, +1) and ( +sqrt(2)/2, +sqrt(2)/2, 0).

Changes From GLUT

GLUT does not include these functions.

15.10  glutWireTeapot, glutSolidTeapot

The "glutWireTeapot" and "glutSolidTeapot" functions draw a wireframe and solid teapot respectively.

Usage

void glutWireTeapot ( GLdouble dSize ) ;

void glutSolidTeapot ( GLdouble dSize ) ;

dSize         The desired size of the teapot

Description

The "glutWireTeapot" and " glutSolidTeapot" functions render a teapot of the desired size, centered at the origin.  This is the famous OpenGL teapot [add reference].

Changes From GLUT

None that we know of.

16.0  Game Mode Functions

16.1  glutGameModeString

16.2  glutEnterGameMode, glutLeaveGameMode

16.3  glutGameModeGet

17.0  Video Resize Functions

17.1  glutVideoResizeGet

17.2  glutSetupVideoResizing, glutStopVideoResizing

17.3  glutVideoResize

17.4  glutVideoPan

18.0  Color Map Functions

18.1  glutSetColor, glutGetColor

18.2  glutCopyColormap

19.0  Miscellaneous Functions

19.1  glutIgnoreKeyRepeat, glutSetKeyRepeat

19.2  glutForceJoystickFunc

19.3  glutReportErrors

20.0  Usage Notes

The following environment variables are recognized by freeglut:

21.0  Implementation Notes

22.0  GLUT State

23.0  "freeglut.h" Header File

24.0  References

25.0  Index