Thanks BB

He he.. I've already lost count of my coffee intake today... but the confusion is still there ;-)

Yup, as I say, when I render a more lightweight scene, or probably anything up to average... it seems to quite happily eat up around 650% to 700% of hyperthreads (of the 800% total)... for all three passes, IDL, SSS and final render pass.

So, the "problem" does seem only to present itself once a scene has gone beyond a certain level of complexity. I guess maybe in terms of figure count... or perhaps light count.

I never use a lot of lights... but for instance I'm doing a scene at the moment and this was, I recall now, rendering at full pelt when just IDL with envsphere (no lights).

So... thinking about it, it's only since adding some point lights and a couple of spots to it, that I've noticed the 25% constriction apparently manifest...

...thinking about it I have added about six points now... where the real lights are in the set I'm using...

...so that's interesting. I will experiment some more too I think...