Hi Grant,
Many thanks for the suggestion ...
Yes, I did think of that - but :-
1. Turning ambient light off didn't change the rendering very much because its set to a very low 5%;
2. I'd expect the ambient light setting to have the same effect (more or less) regardless of which shader is used.
Another few clues ...
1. If I turn all off all the interior lights, then the view is the same whether the 'Limit Shader render mode to 8 lights' setting is on or off.
This is the expected behaviour.
2. With 'Limit Shader render mode to 8 lights' turned ON, successively enabling each interior light has almost no impact on ambient lighting.
You just get the tracing of the interior lights, occluded by walls etc.
Again, this is the expected behaviour.
This is what you see in image #1 above.
3. BUT - with the 'Limit Shader render mode to 8 lights' setting turned OFF, successively enabling each interior light progressively increases the ambient lighting.
You still get the tracing of the interior lights, occluded by walls etc, but the effect is swamped by the ambient lighting.
This is not the expected behaviour.
This is what you see in image #2 above.
4. This is the clincher !!
Next, I turned all the interior lights OFF, then added interior lights one at a time ...
Lighting was correct for the first 6 lights - that is, all the interior lighting was as expected, with traces to the outside occluded by walls - see image #1 below.
BUT - when I turn on the 7th light, the entire exterior lights up ! See image #2 below.
This always happens when the 7th light is turned on, regardless of which other lights are turned on, or the order in which they are enabled.
IMHO - this has to be a bug in the renderer and the 'Limit Shader render mode to 8 lights' setting ?!?!?