Rebuild only one lightmap or object

As several objects are packed together in a single lightmap i guess rebuilding only one object’s GI doesn’t have more sense. So my question is : is there a way to only rebuild one lightmap ?

To the best of my knowledge, no.

However, if you keep your “GI Cache” relatively high (around 10 GB or so, per project), then lightmap baking process goes fast relatively fast since a lot of unchanged things are loaded from cache. Saved a lot of time on my side if I just change the material on one object or such.

Do be warned, if you change something like a directional light that affects your whole scene, or change Terrain properties, it will have to do entire rebake at once. My suggestion: Don’t use lightmap baking as iterative design process. Go as far as you can in designing and compositing your level, try to predict as best as you can how stuff will look like. Then just bake once or twice when making a build or such, with minor tweaks if needed.

GI cache option is in:
Edit → Preferences, then “GI Cache” tab.

Thanks for your input !
(And sorry for the delay of my answer)