Off-screen Rendering
+Off-screen Rendering
-Mesa 1.2.4 introduced off-screen rendering, a facility for generating -3-D imagery without having to open a window on your display. Mesa's -simple off-screen rendering interface is completely operating system -and window system independent so programs which use off-screen -rendering should be very portable. This feature effectively -enables you to use Mesa as an off-line, batch-oriented renderer. +Mesa's off-screen interface is used for rendering into user-allocated memory +without any sort of window system or operating system dependencies. +That is, the GL_FRONT colorbuffer is actually a buffer in main memory, +rather than a window on your display.
+-The "OSMesa" API provides 3 functions for making off-screen +The OSMesa API provides three basic functions for making off-screen renderings: OSMesaCreateContext(), OSMesaMakeCurrent(), and OSMesaDestroyContext(). See the Mesa/include/GL/osmesa.h header for -more information. See the demos/osdemo.c file for an example program. -There is no facility for writing images to files. That's up to you. +more information about the API functions.
+-If you want to generate large images (larger than 1280x1024) you'll -have to edit the src/config.h file to change MAX_WIDTH and MAX_HEIGHT -then recompile Mesa. Image size should only be limited by available -memory. +The OSMesa interface may be used with any of three software renderers:
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- llvmpipe - this is the high-performance Gallium LLVM driver +
- softpipe - this it the reference Gallium software driver +
- swrast - this is the legacy Mesa software rasterizer +
Deep color channels
-- For some applications 8-bit color channels don't have sufficient - accuracy (film and IBR, for example). If you're in this situation - you'll be happy to know that Mesa supports 16-bit and 32-bit color - channels through the OSMesa interface. When using 16-bit channels, - channels are GLushorts and RGBA pixels occupy 8 bytes. When using 32-bit - channels, channels are GLfloats and RGBA pixels occupy 16 bytes. +There are several examples of OSMesa in the mesa/demos repository.
+ +Building OSMesa
+- To build Mesa/OSMesa with 16-bit color channels: -
- cd Mesa-5.x/src - make -f Makefile.X11 clean - make -f Makefile.OSMesa16 linux-osmesa16 -+Configure and build Mesa with something like: - For 32-bit channels:
- cd Mesa-5.x/src - make -f Makefile.X11 clean - make -f Makefile.OSMesa16 linux-osmesa32 +configure --enable-osmesa --disable-driglx-direct --disable-dri --with-gallium-drivers=swrast +make
-You'll wind up with a library named libOSMesa16.so or libOSMesa32.so. +Make sure you have LLVM installed first if you want to use the llvmpipe driver.
-If you're not using Linux, you can easily edit Make-config and add -an appropriate configuration. +When the build is complete you should find:
++lib/libOSMesa.so (swrast-based OSMesa) +lib/gallium/libOSMsea.so (gallium-based OSMesa) ++
-The Mesa/tests/osdemo16.c file (available via CVS) demonstrates how -to use this feature. +Set your LD_LIBRARY_PATH to point to one directory or the other to select +the library you want to use.
+-BE WARNED: 16 and 32-bit channel support has not been exhaustively -tested and there may be some bugs. However, a number of people have -been using this feature successfully so it can't be too broken. +When you link your application, link with -lOSMesa
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