The progressive lightmapper is a path tracing based lightmapper backend that provides baked lightmaps and light probes with progressive updates in the Editor.
The progressive lightmapper goes through a short prepare step (geometry and instance updates, G-buffer and chart mask generation) and starts producing the output very quickly. New lightmaps and light probes are shown as soon as a new intermediate result is ready. This allows for a very fast iteration workflow.
The old Enlighten-based lightmapper for baked lightmaps relied on precomputed realtime GI to generate indirect lighting. That was both an advantage, as just changing the lighting could produce new lightmaps fairly quickly, and a disadvantage, as it imposed all the UV layout limitations even for users only interested in baking. The UV requirements in the progressive lightmapper are the usual for baked lightmapping: non-overlapping UVs with small area and angle errors, and sensible padding between the charts.
The new lightmapper starts producing the output immediately and progressively refines it over time for a much improved lighting workflow - this means an interactive lighting workflow. Additionally, baking times are much more predictable.
See an in-depth video showing the interactive workflow here.
Moreover the new technique bakes global illumination at the lightmap resolution - for each texel individually - without upsampling schemes or relying on any irradiance caches or other global data structures. This makes it robust and allows you to bake selected portions of lightmaps, which means that iteration speed can be improved greatly.
Newly created scenes have the progressive lightmapper enabled by default. Existing scenes will stick to Enlighten until you choose the “Progressive (experimental)” Bake Backend.
The panel below the ‘Auto Generate’ and ‘Generate Lighting’ options shows the amount of lightmaps that were created, how many are in view (converged / not converged) and out of view (converged / not converged) and the bake performance.
In addition to the Baked GI settings in the Lighting window, there are new parameters in the Lightmap Parameters asset that can be configured. These are Anti-aliasing Samples, Pushoff and Backface Tolerance. Default lightmap parameters can be set for the scene in General GI > Default Parameters or set per renderer.
The rest is the default Unity 5 workflow. Mark your objects as static and set some light inputs (lights, environment lighting or emissive materials on static objects) as baked.
In “Auto” mode the lightmaps and light probes will be calculated automatically. If you have “Auto” disabled you will need to press the “Build” button for the bake to start.
Force stop: Allows for stopping the bake at an arbitrary point in time, before the requested amount of samples has actually been done. It works when the lighting is built manually. With the 100,000 max sample count and the ability to disable view prioritization, one can leave the machine baking and just stop whenever the results look pleasing.
Invalid texels: Texels are marked as invalid based on the Backface Tolerance parameter (LightmapParameters > General GI) and invalid texels are filled from the valid neighbours. The dilation process that takes care of that does more iterations once the lightmap has converged than when it’s still improving.
Supersampling: The lighting quality is influenced by the supersampling amount. Control it using the ‘Anti-aliasing Samples’ property (Lightmap Parameters > Baked GI, see the Lightmap Parameters section above).
This project is set up with the settings needed for the progressive lightmapper. It is a version of the Tanks! project also available on the Asset Store. It bakes in less than 5 minutes and has 11 1024x1024 lightmaps. Watch a video showing the interactive workflow in this project.