... at least one I'm willing to let loose. Uses some modest IDL and a quadratic falloff main light. Comments welcome.

Whichway

Well, if I could figure out how to attach it, it would be here.
Ah, needs to be dinky.

Here's the one I've been struggling to get out. The only illumination is a single, quadratic point light. There are grey fill cards off camera to left and top; IDL is bouncing off those to bring out the dark side of his face. There is a floor and concrete slab he is standing on. Otherwise, it is an empty scene.

I had originally set this up in Poser 7 for a challenge and used Gather nodes for the fill. The IDL does a very much better job on the skin amongst the gold around his neck.

If piz99 drops by, I'd appreciate a blotchiness evaluation. Looks pretty good to me, but probaably too simple to trigger those artifacts.

Comments requested.

Whichway

Since the pic is so small and the background is so close to black it's hard to say.  Although your composition is of the kind that is absolutely most favorable for avoiding most of the artifacts - apparently you're set to 1 bounce, which means almost all of the surfaces we see illuminated in the frame are getting direct light from your pointlight.  Where you'd see serious problems would be in the area behind his head, which is unfortunately completely black (0/0/0 RGB) - total black is something you pretty much should never see in a GI image, this means that no GI light actually got shed there.  If this was your intention, great, but it is not good behavior to get from a GI render. 

Fair enough, and thanks for the comments. This one was supposed to be quick since I'd already had it set up. I'll see if I can find something more ambitious.

Whichway

please try it with a corner prop background comprised of three coloured boxes normal to each other.  smoothing off, DM shadows, no ibl, no AO shader nodes.

Why would I want DM shadows? Ray tracing has to be on anyway for IDL to work. The Silver Guy post has no AO shaders and no IBL. I can change the color of the cards easily enough.

Whichway

have noticed some artifacts in IDL renders here, hence interested in checking as many variables as possible.  also, please post render settings if possible.

The places to pay most attention to are the areas that are only getting lit by bounced light, that's where the artifacts show up the worst - although they also show up in places that are getting direct light, it's just drastically worse on surfaces that are only getting bounce light.

Huh. I started a render of the Silver Guy with fully saturated, 100% Difuse colors on the backdrop and two "fill" cards. Before P8 vanished during the render (told you this one was a struggle) there was effectively no color apparent, i.e., no IDL! I wonder how what little light hits the right side of his face gets there?

Whichway