Now that i've spent some time looking through the code and playing around with the light layers in Blendigo I must say that the idea behind its implementation is rather clever. It just leaves to be desired for certain light sources HDRI (Hemi) IES and Sun light sources.
What I mean with clever requires of course some explanation.
Lets assume we have a scene with several light sources somewhat coarsely defined in Blender/Blendigo but definitely in need of tuning. Once the render button is clicked the export starts and Indigo begins to render. The user determines quickly that this lighting setup does not work. The render is stopped, Indigo closed and gain is adjusted in Blendigo. Another render is started.....and on...and on....
That is a somewhat tedious workflow and unacceptable for more complex scenes with more "stuff" to export.
But of course Indigo offers adjustability of the light layers in its own UI. So the user decides to forego the back-and-forth between Blender und Indigo and comfortably adjusts the light layer gain to his satisfaction in Indigo.
IIRC, increasing the light layer gain does not increase/decrease the output power of a light source. As such when the gain of a previously dim light source ( which due its lower light output was not sampled so often by Indigo ) is increased, the noise that is still present in that light layer is equally amplified.
In order to achieve a more noise free rendering a user now has to manually calculate/scale the output power of all the light sources in the scene proportionally to the light layer gain settings in Indigo. That is an equally tedious undertaking and can be a real PITA if the individual light layers contain more than one light source.
This is where Bendigo's implementation of light layer gain comes in extremely handy!
As was explained earlier in this thread Blendigo manipulates the output power of the light sources directly according to the layer gain setting in Blendigo. Once the light layer gain is adjusted in Indigo, all a user has to do now is transfer the gain values from Indigo to the Blendigo light layer gain setting and voilà on export Blendigo scales all the light source output power settings according to the light layer settings.
The "Merge Light Layers" check box also on export actually moves all the correctly scaled light sources to the default layer 0 . The original settings in Blendigo are not manipulated.
The idea behind this is obvious, Blendigo and Indigo are to be understood as complimentary tools. That allows for a very nice workflow to quickly get to a final render! Ingenious!
This could be made much better integrated if Indigo could render interactively in Blenders viewport but for now - and of course with the exception of the previously named light sources Hemi, IES and Sun - I find that the way it is currently implemented should possibly be left untouched or perhaps it can be extended for Emission Scale.
Also what is thinkable is to treat these three special light sources well, special in the sense that only these would receive the "normal" indigo light layer treatment.
Please provide feedback if all this makes sense
