Assigning lightmap UVs without contributing to lighting

Hello!

In our game we switch lightmaps at runtime. We also do this after performing a static combine, so it's important that each of the lightmaps have the same UV layout.

In Unity 4, this was easy: bake once as a "UV" pass with all game objects enabled. Then lockAtlas and disable game objects that shouldn't contribute to the scene for each of the subsequent bakes. (Some game objects must be disabled during baking of certain lightmaps, such as shadow casters, etc.).

In Unity 5, there is no more "lockAtlas" functionality, so if I enable/disable any game objects with renderers the UV layout will change. This means I must have all the renderers active during any of the bakes to "save them a spot" on the lightmap UV layout.

But I still want to prevent these certain game objects from contributing to the lighting, even though their renderer is active. How do I do this?

I have tried changing these objects to use transparent shaders and no material at all, but the objects still contribute to indirect lighting. Disabling shadows is easy, but these objects always seem to affect the indirect lighting in the scene.

Ideas?

EDIT: it's easy to get an object to not reflect light (a transparent shader that returns (0,0,0,0) seems to work)... But I'm specifically having a hard time preventing an object from blocking indirect light. No matter what shader or material configuration I use, it seems that my objects are always blocking indirect light.

 

Hmm... I remember there was a bug listed somewhere that objects would still block indirect light, even when "Cast Shadows" is set to "off". I guess this is likely the cause of the problems I'm having... Too bad transparent objects also seem block indirect light.

Please let me know if you figure out a way to get around this bug/limitation...

 

If you have a transparent material you should create a new set of lightmap parameters and set in that lightmap parameters the opon for transparent. Then asine the transparent mesh that lightmap parameters and its working fine. That would work too for stuff that should not influence the scene.