Hello,
Is there an implementation/driver that supports software fallback whenever a feature not part of the specified core version is not present? This way I can make sure my program will run even if the hardware or drivers dont support the required version.
Is Mesa3D the way to go?
Thanks.
Is there an implementation/driver that supports software fallback whenever a feature not part of the specified core version is not present?
With the exception of GLSL and the implementation-dependent limits, OpenGL implementations are required to do whatever you tell them, whether hardware or software. So if some spec-defined behavior fails, it’s a driver bug.
What feature are you talking about? Imaging subset?
Is Mesa3D the way to go?
I don’t know. Is there anything other then Mesa and that offers a GL API at the same time?
The Mesa3D software renderer is ridiculously slow and therefore unusable.
Still, it’s better than Microsoft’s dreaded GDI software renderer. 
Mesa3D with the new Gallium3D softpipe driver should be quite a bit faster than the current implementation. The whole stack is undergoing some significant improvements and should become quite usable during in 2010 (with OpenGL 3.0+ support and several new APIs like OpenCL, OpenVG, …)
Besides, what’s the alternative?
I meant swrast (in the src/mesa tree), which is the default software driver, not softpipe.
Concerning Gallium3D, as far as I know, the softpipe driver will stay as it is: a slow reference rasterizer. However, they are planning to add another pipe driver that will be optimized for performance and to scale well on multi-core CPUs (I guess the proposed name was llvmpipe, but I am not sure).