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diff --git a/mesalib/docs/README.CYGWIN b/mesalib/docs/README.CYGWIN new file mode 100644 index 000000000..58d5af3e2 --- /dev/null +++ b/mesalib/docs/README.CYGWIN @@ -0,0 +1,256 @@ + + Mesa Cygwin/X11 Information + + +WARNING +======= + +If you installed X11 (packages xorg-x11-devel and xorg-x11-bin-dlls ) with the +latest setup.exe from Cygwin the GL (Mesa) libraries and include are already +installed in /usr/X11R6. + +The following will explain how to "replace" them. + +Installation +============ + +How to compile Mesa on Cygwin/X11 systems: + +1. Shared libs: + type 'make cygwin-sl'. + + When finished, the Mesa DLL will be in the Mesa-x.y/lib/ and + Mesa-x.y/bin directories. + + +2. Static libs: + type 'make cygwin-static'. + When finished, the Mesa libraries will be in the Mesa-x.y/lib/ directory. + +Header and library files: + After you've compiled Mesa and tried the demos I recommend the following + procedure for "installing" Mesa. + + Copy the Mesa include/GL directory to /usr/X11R6/include: + cp -a include/GL /usr/X11R6/include + + Copy the Mesa library files to /usr/X11R6/lib: + cp -a lib/* /usr/X11R6ocal/lib + + Copy the Mesa bin files (used by the DLL stuff) to /usr/X11R6/bin: + cp -a lib/cyg* /usr/X11R6/bin + +Xt/Motif widgets: + If you want to use Mesa or OpenGL in your Xt/Motif program you can build + the widgets found in either the widgets-mesa or widgets-sgi directories. + The former were written for Mesa and the later are the original SGI + widgets. Look in those directories for more information. + For the Motif widgets you must have downloaded the lesstif package. + + +Using the library +================= + +Configuration options: + The file src/mesa/main/config.h has many parameters which you can adjust + such as maximum number of lights, clipping planes, maximum texture size, + etc. In particular, you may want to change DEPTH_BITS from 16 to 32 + if a 16-bit depth buffer isn't precise enough for your application. + + +Shared libraries: + If you compile shared libraries (Win32 DLLS) you may have to set an + environment variable to specify where the Mesa libraries are located. + Set the PATH variable to include /your-dir/Mesa-2.6/bin. + Otherwise, when you try to run a demo it may fail with a message saying + that one or more DLL couldn't be found. + + +Xt/Motif Widgets: + Two versions of the Xt/Motif OpenGL drawing area widgets are included: + + widgets-sgi/ SGI's stock widgets + widgets-mesa/ Mesa-tuned widgets + + Look in those directories for details + + +Togl: + Togl is an OpenGL/Mesa widget for Tcl/Tk. + See http://togl.sourceforge.net for more information. + + + +X Display Modes: + Mesa supports RGB(A) rendering into almost any X visual type and depth. + + The glXChooseVisual function tries its best to pick an appropriate visual + for the given attribute list. However, if this doesn't suit your needs + you can force Mesa to use any X visual you want (any supported by your + X server that is) by setting the MESA_RGB_VISUAL and MESA_CI_VISUAL + environment variables. When an RGB visual is requested, glXChooseVisual + will first look if the MESA_RGB_VISUAL variable is defined. If so, it + will try to use the specified visual. Similarly, when a color index + visual is requested, glXChooseVisual will look for the MESA_CI_VISUAL + variable. + + The format of accepted values is: <visual-class> <depth> + Here are some examples: + + using the C-shell: + % setenv MESA_RGB_VISUAL "TrueColor 8" // 8-bit TrueColor + % setenv MESA_CI_VISUAL "PseudoColor 12" // 12-bit PseudoColor + % setenv MESA_RGB_VISUAL "PseudoColor 8" // 8-bit PseudoColor + + using the KornShell: + $ export MESA_RGB_VISUAL="TrueColor 8" + $ export MESA_CI_VISUAL="PseudoColor 12" + $ export MESA_RGB_VISUAL="PseudoColor 8" + + +Double buffering: + Mesa can use either an X Pixmap or XImage as the backbuffer when in + double buffer mode. Using GLX, the default is to use an XImage. The + MESA_BACK_BUFFER environment variable can override this. The valid + values for MESA_BACK_BUFFER are: Pixmap and XImage (only the first + letter is checked, case doesn't matter). + + A pixmap is faster when drawing simple lines and polygons while an + XImage is faster when Mesa has to do pixel-by-pixel rendering. If you + need depth buffering the XImage will almost surely be faster. Exper- + iment with the MESA_BACK_BUFFER variable to see which is faster for + your application. + + +Colormaps: + When using Mesa directly or with GLX, it's up to the application writer + to create a window with an appropriate colormap. The aux, tk, and GLUT + toolkits try to minimize colormap "flashing" by sharing colormaps when + possible. Specifically, if the visual and depth of the window matches + that of the root window, the root window's colormap will be shared by + the Mesa window. Otherwise, a new, private colormap will be allocated. + + When sharing the root colormap, Mesa may be unable to allocate the colors + it needs, resulting in poor color quality. This can happen when a + large number of colorcells in the root colormap are already allocated. + To prevent colormap sharing in aux, tk and GLUT, define the environment + variable MESA_PRIVATE_CMAP. The value isn't significant. + + +Gamma correction: + To compensate for the nonlinear relationship between pixel values + and displayed intensities, there is a gamma correction feature in + Mesa. Some systems, such as Silicon Graphics, support gamma + correction in hardware (man gamma) so you won't need to use Mesa's + gamma facility. Other systems, however, may need gamma adjustment + to produce images which look correct. If in the past you thought + Mesa's images were too dim, read on. + + Gamma correction is controlled with the MESA_GAMMA environment + variable. Its value is of the form "Gr Gg Gb" or just "G" where + Gr is the red gamma value, Gg is the green gamma value, Gb is the + blue gamma value and G is one gamma value to use for all three + channels. Each value is a positive real number typically in the + range 1.0 to 2.5. The defaults are all 1.0, effectively disabling + gamma correction. Examples using csh: + + % setenv MESA_GAMMA "2.3 2.2 2.4" // separate R,G,B values + % setenv MESA_GAMMA "2.0" // same gamma for R,G,B + + The demos/gamma.c program may help you to determine reasonable gamma + value for your display. With correct gamma values, the color intensities + displayed in the top row (drawn by dithering) should nearly match those + in the bottom row (drawn as grays). + + Alex De Bruyn reports that gamma values of 1.6, 1.6 and 1.9 work well + on HP displays using the HP-ColorRecovery technology. + + Mesa implements gamma correction with a lookup table which translates + a "linear" pixel value to a gamma-corrected pixel value. There is a + small performance penalty. Gamma correction only works in RGB mode. + Also be aware that pixel values read back from the frame buffer will + not be "un-corrected" so glReadPixels may not return the same data + drawn with glDrawPixels. + + For more information about gamma correction see: + http://www.inforamp.net/~poynton/notes/colour_and_gamma/GammaFAQ.html + + +Overlay Planes + + Overlay planes in the frame buffer are supported by Mesa but require + hardware and X server support. To determine if your X server has + overlay support you can test for the SERVER_OVERLAY_VISUALS property: + + xprop -root | grep SERVER_OVERLAY_VISUALS + + +HPCR glClear(GL_COLOR_BUFFER_BIT) dithering + + If you set the MESA_HPCR_CLEAR environment variable then dithering + will be used when clearing the color buffer. This is only applicable + to HP systems with the HPCR (Color Recovery) system. + + +Extensions +========== + There are three Mesa-specific GLX extensions at this time. + + GLX_MESA_pixmap_colormap + + This extension adds the GLX function: + + GLXPixmap glXCreateGLXPixmapMESA( Display *dpy, XVisualInfo *visual, + Pixmap pixmap, Colormap cmap ) + + It is an alternative to the standard glXCreateGLXPixmap() function. + Since Mesa supports RGB rendering into any X visual, not just True- + Color or DirectColor, Mesa needs colormap information to convert RGB + values into pixel values. An X window carries this information but a + pixmap does not. This function associates a colormap to a GLX pixmap. + See the xdemos/glxpixmap.c file for an example of how to use this + extension. + + GLX_MESA_release_buffers + + Mesa associates a set of ancillary (depth, accumulation, stencil and + alpha) buffers with each X window it draws into. These ancillary + buffers are allocated for each X window the first time the X window + is passed to glXMakeCurrent(). Mesa, however, can't detect when an + X window has been destroyed in order to free the ancillary buffers. + + The best it can do is to check for recently destroyed windows whenever + the client calls the glXCreateContext() or glXDestroyContext() + functions. This may not be sufficient in all situations though. + + The GLX_MESA_release_buffers extension allows a client to explicitly + deallocate the ancillary buffers by calling glxReleaseBuffersMESA() + just before an X window is destroyed. For example: + + #ifdef GLX_MESA_release_buffers + glXReleaseBuffersMESA( dpy, window ); + #endif + XDestroyWindow( dpy, window ); + + This extension is new in Mesa 2.0. + + GLX_MESA_copy_sub_buffer + + This extension adds the glXCopySubBufferMESA() function. It works + like glXSwapBuffers() but only copies a sub-region of the window + instead of the whole window. + + This extension is new in Mesa version 2.6 + + + +Summary of X-related environment variables: + MESA_RGB_VISUAL - specifies the X visual and depth for RGB mode (X only) + MESA_CI_VISUAL - specifies the X visual and depth for CI mode (X only) + MESA_BACK_BUFFER - specifies how to implement the back color buffer (X only) + MESA_PRIVATE_CMAP - force aux/tk libraries to use private colormaps (X only) + MESA_GAMMA - gamma correction coefficients (X only) + + +---------------------------------------------------------------------- +README.CYGWIN - lassauge April 2004 - based on README.X11 |