I'm currently interested in writing a lightmap generator for the old Quake3 BSP format as a side project and was wondering what techniques the latest and greatest lightmap generators are using. I've come across a few such as photon mapping of some sort (UE4), rasterization + irradiance gradients (The Witness), and as far as I can tell the map compiler for Quake3 used some radiosity-based technique.
What techniques are games using nowadays? I'm looking for something which gives fast convergence and doesn't require too much tweaking to get the desired results. I initially thought to use photon mapping and actually made a start, but I thought it would be good to get some more opinions first. I'm initially writing this for CPU, and then moving to GPU when I have a good understanding of how the algorithm works. Any advice is welcome :D