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 three basic functions for making off-screen renderings: OSMesaCreateContext(), OSMesaMakeCurrent(), and OSMesaDestroyContext(). See the Mesa/include/GL/osmesa.h header for more information about the API functions.
The OSMesa interface may be used with any of three software renderers:
- 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
There are several examples of OSMesa in the mesa/demos repository.
Configure and build Mesa with something like:
meson builddir -Dosmesa=gallium -Dgallium-drivers=swrast -Ddri-drivers= -Dvulkan-drivers= -Dprefix=$PWD/builddir/install ninja -C builddir install
Make sure you have LLVM installed first if you want to use the llvmpipe driver.
When the build is complete you should find:
$PWD/builddir/install/lib/libOSMesa.so (swrast-based OSMesa) $PWD/builddir/install/lib/gallium/libOSMsea.so (gallium-based OSMesa)
Set your LD_LIBRARY_PATH to point to $PWD/builddir/install to use the libraries
When you link your application, link with -lOSMesa