The Mesa 3D Graphics Library

# Off-screen Rendering

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:

1. llvmpipe - this is the high-performance Gallium LLVM driver
2. softpipe - this it the reference Gallium software driver
3. swrast - this is the legacy Mesa software rasterizer

There are several examples of OSMesa in the mesa/demos repository.

## Building OSMesa

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