Back in 2007 we all went to visionday at DTU (Danish Technical University)
And among the speakers were Rune Vendler who presented a super simple and awesome way to simulate the flow of light by using a grid and a blur kernel.
Everybody immediately went home a did their own version of this method, mainly because Runes demos were very impressive. There is a link to the slides below.
Here are some screens from my implementation, that features transparent objects as well. To this day (2018) it still looks pretty convincing and there is some special vibe to the quality of the light. That maybe could be used in some indie game 🙂
Later on we tried to use it during our Lego collaboration, and use some Cuda based voxelization to create the grid. But when using the method with more complex and round geometry it does not such a great job. And better methods has been developed like Light Propagation Volumes and Voxel cone tracing.