The Open-Source
OpenGL Utility Toolkit
(freeglut 2.0.0)
Application Programming Interface

Version 4.0

The freeglut Programming Consortium
July, 2003

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. Contents

  1. Contents
  2. Introduction
  3. Background
    1. Design Philosophy
    2. Conventions
    3. Terminology
    4. Differences from GLUT 3.7
  4. Initialization Functions
    1. glutInit
    2. glutInitWindowPosition, glutInitWindowSize
    3. glutInitDisplayMode
    4. glutInitDisplayString
  5. Event Processing Functions
    1. glutMainLoop
    2. glutMainLoopEvent
    3. glutLeaveMainLoop
  6. Window Functions
    1. glutCreateWindow
    2. glutCreateSubwindow
    3. glutDestroyWindow
    4. glutSetWindow, glutGetWindow
    5. glutSetWindowTitle, glutSetIconTitlew
    6. glutReshapeWindow
    7. glutPositionWindow
    8. glutShowWindow, glutHideWindow, glutIconifyWindow
    9. glutPushWindow, glutPopWindow
    10. glutFullScreen
  7. Display Functions
    1. glutPostRedisplay
    2. glutPostWindowRedisplay
    3. glutSwapBuffers
  8. Mouse Cursor Functions
    1. glutSetCursor
    2. glutWarpPointer
  9. Overlay Functions
    1. glutEstablishOverlay
    2. glutRemoveOverlay
    3. glutUseLayer
    4. glutPostOverlayRedisplay
    5. glutPostWindowOverlayRedisplay
    6. glutShowOverlay, glutHideOverlay
  10. Menu Functions
    1. glutCreateMenu
    2. glutDestroyMenu
    3. glutGetMenu, glutSetMenu
    4. glutAddMenuEntry
    5. glutAddSubMenu
    6. glutChangeToMenuEntry
    7. glutChangeToSubMenu
    8. glutRemoveMenuItem
    9. glutAttachMenu, glutDetachMenu
  11. Global Callback Registration Functions
    1. glutTimerFunc
    2. glutIdleFunc
  12. Window-Specific Callback Registration Functions
    1. glutDisplayFunc
    2. glutOverlayDisplayFunc
    3. glutReshapeFunc
    4. glutKeyboardFunc
    5. glutSpecialFunc
    6. glutKeyboardUpFunc
    7. glutSpecialUpFunc
    8. glutMotionFunc, glutPassiveMotionFunc
    9. glutVisibilityFunc
    10. glutEntryFunc
    11. glutJoystickFunc
    12. glutSpaceballMotionFunc
    13. glutSpaceballRotateFunc
    14. glutSpaceballButtonFunc
    15. glutButtonBoxFunc
    16. glutDialsFunc
    17. glutTabletMotionFunc
    18. glutTabletButtonFunc
    19. glutMenuStatusFunc
    20. glutWindowStatusFunc
  13. State Setting and Retrieval Functions
    1. glutSetOption
    2. glutGet
    3. glutDeviceGet
    4. glutGetModifiers
    5. glutLayerGet
    6. glutExtensionSupported
    7. glutGetProcAddress
  14. Font Rendering Functions
    1. glutBitmapCharacter
    2. glutBitmapString
    3. glutBitmapWidth
    4. glutBitmapLength
    5. glutBitmapHeight
    6. glutStrokeCharacter
    7. glutStrokeString
    8. glutStrokeWidth
    9. glutStrokeLength
    10. glutStrokeHeight
  15. Geometric Object Rendering Functions
    1. glutWireSphere, glutSolidSphere
    2. glutWireTorus, glutSolidTorus
    3. glutWireCone, glutSolidCone
    4. glutWireCube, glutSolidCube
    5. glutWireTetrahedron, glutSolidTetrahedron
    6. glutWireOctahedron, glutSolidOctahedron
    7. glutWireDodecahedron, glutSolidDodecahedron
    8. glutWireIcosahedron, glutSolidIcosahedron
    9. glutWireRhombicDodecahedron, glutSolidRhombicDodecahedron
    10. glutWireTeapot, glutSolidTeapot
  16. Game Mode Functions
    1. glutGameModeString
    2. glutEnterGameMode, glutLeaveGameMode
    3. glutGameModeGet
  17. Video Resize Functions
    1. glutVideoResizeGet
    2. glutSetupVideoResizing, glutStopVideoResizing
    3. glutVideoResize
    4. glutVideoPan
  18. Color Map Functions
    1. glutSetColor, glutGetColor
    2. glutCopyColormap
  19. Miscellaneous Functions
    1. glutIgnoreKeyRepeat, glutSetKeyRepeat
    2. glutForceJoystickFunc
    3. glutReportErrors
  20. Usage Notes
    1. Implementation Notes
    2. GLUT State
    3. "freeglut.h" Header File
    4. References
    5. Index

2. Introduction

3. 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. 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. 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. 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. Display Functions

7.1 glutPostRedisplay

7.2 glutPostWindowRedisplay

7.3 glutSwapBuffers

8. Mouse Cursor Functions

8.1 glutSetCursor

8.2 glutWarpPointer

9. 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. 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. 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 ) );

funcThe 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. 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 freeglutProgramming 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 glutSpecialUpFuncfunction 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. State Setting and Retrieval Functions

13.1 glutSetOption

13.2 glutGet

The following state variables may be queried with glutGet. The returned value is an integer.

These queries are with respect to the current window:

These queries do not depend on the current window.

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.

Changes From GLUT

GLUT does not include this function.

14. 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 );

fontThe stroke font to use in rendering the character
characterThe 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. 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. Game Mode Functions

16.1 glutGameModeString

16.2 glutEnterGameMode, glutLeaveGameMode

16.3 glutGameModeGet

17. Video Resize Functions

17.1 glutVideoResizeGet

17.2 glutSetupVideoResizing, glutStopVideoResizing

17.3 glutVideoResize

17.4 glutVideoPan

18. Color Map Functions

18.1 glutSetColor, glutGetColor

18.2 glutCopyColormap

19. Miscellaneous Functions

19.1 glutIgnoreKeyRepeat, glutSetKeyRepeat

19.2 glutForceJoystickFunc

19.3 glutReportErrors

20. Usage Notes

The following environment variables are recognized by freeglut:

21. Implementation Notes

22. GLUT State

23. "freeglut.h" Header File

Application programmers who are porting their GLUT programs to freeglut may continue to include <GL/glut.h> in their programs. Programs which use the freeglut-specific extensions to GLUT should include <GL/freeglut.h>. One possible arrangement is as follows:

#ifdef FREEGLUT
#include <GL/freeglut_ext.h>
#else
#include <GL/glut.h>
#endif

Compile-time freeglut version testing can be done as follows:

#ifdef FREEGLUT_VERSION_2_0
  code specific to freeglut 2.0 or later here
#endif

In future releases, FREEGLUT_VERSION_2_1, FREEGLUT_VERSION_2_2, etc will be defined. This scheme mimics OpenGL conventions.

The freeglut version can be queried at runtime by calling glutGet(GLUT_VERSION). The result will be X*10000+Y*100+Z where X is the major version, Y is the minor version and Z is the patch level.

This may be used as follows:

if (glutGet(GLUT_VERSION) < 20001) {
    printf("Sorry, you need freeglut version 2.0.1 or later to run this program.\n");
    exit(1);
}

24. References

25. Index