glXIntro man page on RedHat
[printable version]
GLXINTRO(3G) OpenGL Manual GLXINTRO(3G)
NAME
glXIntro - Introduction to OpenGL in the X window system
OVERVIEW
OpenGL (called GL in other pages) is a high-performance 3D-oriented
renderer. It is available in the X window system through the GLX
extension. To determine whether the GLX extension is supported by an X
server, and if so, what version is supported, call glXQueryExtension()
and glXQueryVersion().
GLX extended X servers make a subset of their visuals available for
OpenGL rendering. Drawables created with these visual can also be
rendered into using the core X renderer and or any other X extension
that is compatible with all core X visuals.
GLX extends a drawable's standard color buffer with additional buffers.
These buffers include back and auxiliary color buffers, a depth buffer,
a stencil buffer, and a color accumulation buffer. Some or all of the
buffers listed are included in each X visual that supports OpenGL.
GLX supports rendering into three types of drawables: windows, pixmaps,
and pbuffers (pixel buffers). GLX windows and pixmaps are X resources,
and capable of accepting core X rendering as well as OpenGL rendering.
GLX-pbuffers are GLX only resources and might not accept core X
rendering.
To render using OpenGL into a GLX drawable, you must determine the
appropriate GLXFBConfig that supports the rendering features your
application requires. glXChooseFBConfig() returns a GLXFBConfig
matching the required attributes or NULL if no match is found. A
complete list of GLXFBConfigs supported by a server can be obtained by
calling glXGetFBConfigs(). Attributes of a particular GLXFBConfig can
be queried by calling glXGetFBConfigAttrib().
For GLX windows and pixmaps, a suitable X drawable (using either
XCreateWindow or XCreatePixmap, respectively) with a matching visual
must be created first. Call glXGetVisualFromFBConfig() to obtain the
necessary XVisualInfo structure for creating the X drawable. For
pbuffers, no underlying X drawable is required.
To create a GLX window from an X window, call glXCreateWindow().
Likewise, to create a GLX pixmap, call glXCreatePixmap(). Pbuffers are
created by calling glXCreatePbuffer(). Use glXDestroyWindow(),
glXDestroyPixmap(), and glXDestroyPbuffer() to release previously
allocated resources.
A GLX context is required to bind OpenGL rendering to a GLX resource. A
GLX resource and rendering context must have compatible GLXFBConfigs.
To create a GLX context, call glXCreateNewContext(). A context may be
bound to a GLX drawable by using glXMakeContextCurrent(). This
context/drawable pair becomes the current context and current drawable,
and is used by all OpenGL rendering commands until
glXMakeContextCurrent() is called with different arguments.
Both core X and OpenGL commands can be used to operate on drawables;
however, the X and OpenGL command streams are not synchronized.
Synchronization can be explicitly specified using by calling
glXWaitGL(), glXWaitX(), XSync, and XFlush.
EXAMPLES
Below is a minimal example of creating an RGBA-format X window that's
compatible with OpenGL using GLX 1.3 commands. The window is cleared to
yellow when the program runs. The program does minimal error checking;
all return values should be checked.
#include <stdio.h>
#include <stdlib.h>
#include <GL/gl.h>
#include <GL/glx.h>
int singleBufferAttributess[] = {
GLX_DRAWABLE_TYPE, GLX_WINDOW_BIT,
GLX_RENDER_TYPE, GLX_RGBA_BIT,
GLX_RED_SIZE, 1, /* Request a single buffered color buffer */
GLX_GREEN_SIZE, 1, /* with the maximum number of color bits */
GLX_BLUE_SIZE, 1, /* for each component */
None
};
int doubleBufferAttributes[] = {
GLX_DRAWABLE_TYPE, GLX_WINDOW_BIT,
GLX_RENDER_TYPE, GLX_RGBA_BIT,
GLX_DOUBLEBUFFER, True, /* Request a double-buffered color buffer with */
GLX_RED_SIZE, 1, /* the maximum number of bits per component */
GLX_GREEN_SIZE, 1,
GLX_BLUE_SIZE, 1,
None
};
static Bool WaitForNotify( Display *dpy, XEvent *event, XPointer arg ) {
return (event->type == MapNotify) && (event->xmap.window == (Window) arg);
}
int main( int argc, char *argv[] )
{
Display *dpy;
Window xWin;
XEvent event;
XVisualInfo *vInfo;
XSetWindowAttributes swa;
GLXFBConfig *fbConfigs;
GLXContext context;
GLXWindow glxWin;
int swaMask;
int numReturned;
int swapFlag = True;
/* Open a connection to the X server */
dpy = XOpenDisplay( NULL );
if ( dpy == NULL ) {
printf( "Unable to open a connection to the X server\n" );
exit( EXIT_FAILURE );
}
/* Request a suitable framebuffer configuration - try for a double
** buffered configuration first */
fbConfigs = glXChooseFBConfig( dpy, DefaultScreen(dpy),
doubleBufferAttributes, &numReturned );
if ( fbConfigs == NULL ) { /* no double buffered configs available */
fbConfigs = glXChooseFBConfig( dpy, DefaultScreen(dpy),
singleBufferAttributess, &numReturned );
swapFlag = False;
}
/* Create an X colormap and window with a visual matching the first
** returned framebuffer config */
vInfo = glXGetVisualFromFBConfig( dpy, fbConfigs[0] );
swa.border_pixel = 0;
swa.event_mask = StructureNotifyMask;
swa.colormap = XCreateColormap( dpy, RootWindow(dpy, vInfo->screen),
vInfo->visual, AllocNone );
swaMask = CWBorderPixel | CWColormap | CWEventMask;
xWin = XCreateWindow( dpy, RootWindow(dpy, vInfo->screen), 0, 0, 256, 256,
0, vInfo->depth, InputOutput, vInfo->visual,
swaMask, &swa );
/* Create a GLX context for OpenGL rendering */
context = glXCreateNewContext( dpy, fbConfigs[0], GLX_RGBA_TYPE,
NULL, True );
/* Create a GLX window to associate the frame buffer configuration
** with the created X window */
glxWin = glXCreateWindow( dpy, fbConfigs[0], xWin, NULL );
/* Map the window to the screen, and wait for it to appear */
XMapWindow( dpy, xWin );
XIfEvent( dpy, &event, WaitForNotify, (XPointer) xWin );
/* Bind the GLX context to the Window */
glXMakeContextCurrent( dpy, glxWin, glxWin, context );
/* OpenGL rendering ... */
glClearColor( 1.0, 1.0, 0.0, 1.0 );
glClear( GL_COLOR_BUFFER_BIT );
glFlush();
if ( swapFlag )
glXSwapBuffers( dpy, glxWin );
sleep( 10 );
exit( EXIT_SUCCESS );
}
NOTES
An X color map must be created and passed to XCreateWindow.
A GLX context must be created and bound to a GLX drawable before OpenGL
commands can be executed. OpenGL commands executed while no
context/drawable pair is current result in undefined behavior.
Exposure events indicate that all buffers associated with the specified
window may be damaged and should be repainted. Although certain buffers
of some visuals on some systems may never require repainting (the depth
buffer, for example), it is incorrect to write a program assuming that
these buffers will not be damaged.
GLX commands utilize XVisualInfo structures rather than pointers to
visuals or visualIDs directly. XVisualInfo structures contain visual,
visualID, screen, and depth elements, as well as other X-specific
information.
USING GLX EXTENSIONS
All supported GLX extensions will have a corresponding definition in
glx.h and a token in the extension string returned by
glXQueryExtensionsString(). For example, if the EXT_visual_info
extension is supported, then this token will be defined in glx.h and
EXT_visual_info will appear in the extension string returned by
glXQueryExtensionsString(). The definitions in glx.h can be used at
compile time to determine if procedure calls corresponding to an
extension exist in the library.
OpenGL itself is capable of being extended.
GLX 1.1, GLX 1.2, AND GLX 1.3
GLX 1.3 is now supported and is backward compatible with GLX 1.1 and
GLX 1.2. It introduces new functionality (namely GLXFBConfigs) that
supersedes the GLX 1.2 functionality. GLX 1.2 commands are supported,
but their use in new application development is not recommended.
GLX 1.3 corresponds to OpenGL versions 1.2 and introduces the following
new calls: glXGetFBConfigs(), glXGetFBConfigAttrib(),
glXGetVisualFromFBConfig(), glXCreateWindow(), glXDestroyWindow(),
glXCreatePixmap(), glXDestroyPixmap(), glXCreatePbuffer(),
glXDestroyPbuffer(), glXQueryDrawable(), glXCreateNewContext(),
glXMakeContextCurrent(), glXGetCurrentReadDrawable(),
glXGetCurrentDisplay(), glXQueryContext(), and glXSelectEvent(),
glXGetSelectedEvent().
GLX 1.2 corresponds to OpenGL version 1.1 and introduces the following
new call: glXGetCurrentDisplay().
GLX 1.1 corresponds to OpenGL version 1.0 and introduces the following
new calls: glXQueryExtensionsString(), glXQueryServerString(), and
glXGetClientString().
Call glXQueryVersion() to determine at runtime what version of GLX is
available. glXQueryVersion() returns the version that is supported on
the connection. Thus, if 1.3 is returned, both the client and server
support GLX 1.3. You can also check the GLX version at compile time:
GLX_VERSION_1_1 will be defined in glx.h if GLX 1.1 calls are
supported, GLX_VERSION_1_2 will be defined if GLX 1.2 calls are
supported, and GLX_VERSION_1_3 will be defined if GLX 1.3 calls are
supported.
SEE ALSO
glFinish(), glFlush(), glXChooseVisual(), glXCopyContext(),
glXCreateContext(), glXCreateGLXPixmap(), glXCreateNewContext(),
glXCreatePbuffer(), glXCreatePixmap(), glXCreateWindow(),
glXDestroyContext(), glXDestroyPbuffer(), glXDestroyPixmap(),
glXDestroyWindow(), glXGetClientString(), glXGetConfig(),
glXGetCurrentDisplay(), glXGetCurrentReadDrawable(),
glXGetFBConfigAttrib(), glXGetFBConfigs(), glXGetProcAddress(),
glXGetSelectedEvent(), glXGetVisualFromFBConfig(), glXIsDirect(),
glXMakeContextCurrent(), glXMakeCurrent(), glXQueryContext(),
glXQueryDrawable(), glXQueryExtension(), glXQueryExtensionsString(),
glXQueryServerString(), glXQueryVersion(), glXSelectEvent(),
glXSwapBuffers(), glXUseXFont(), glXWaitGL(), glXWaitX().
XCreateColormap, XCreateWindow, XSync
COPYRIGHT
Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed
under the SGI Free Software B License. For details, see
http://oss.sgi.com/projects/FreeB/.
AUTHORS
opengl.org
opengl.org 03/16/2013 GLXINTRO(3G)
[top]
List of man pages available for RedHat
Copyright (c) for man pages and the logo by the respective OS vendor.
For those who want to learn more, the polarhome community provides shell access and support.
[legal]
[privacy]
[GNU]
[policy]
[cookies]
[netiquette]
[sponsors]
[FAQ]
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
|
|
Vote for polarhome
|
