OK, next question. I've been reading and experimenting and learning how to use IDL for indoor scenes and have picked up a fair bit. I have run across a problem that I cannot figure out and have not been able to glean a solution from the threads I've already looked at, so... more questions.

Here's the scene with the light level that is ballpark to what I want;

now pretty much everything in view renders nicely except for the horrible splotchy walls facing the camera. I have tried everything I can think of to get rid of them, but that's difficult if I don't know why those materials and none of the others.

The lighting is 2 lights, one an infinite for the sun at around 800% and the other is a 'fill' point light in the middle of the room at 18% with shadows off. The light bloom on the wall between couches and TV is light leakage around the wall. I reduced the IDL IC to 20 but have kept the main IC between 50 and 90. IDL quality is maxed. I have tried changing the balance between the two lights but no real difference. IC adjustments gave the biggest improvements but not enough. In a fit of desperation I tried using box primitives to mask that wall and it has succeeeded in reducing both the bloom and the marks (see next) but not completely, and it seems a bit of a dodgy solution...

...so can anyone tell me what is really causing those marks? It's like the infinite light is 'burning through' the walls! BTW, I'm using Poser 2012.

Are you using a linear workflow (GC on)? Do you use the D3D script for setting up your render?

See where I have Irradiance Cache set to 20? It needs to be more like 75 or 80 for a scene like this, or indeed turned off by unchecking 'irradiance cache' or setting the value to 100.

It will significantly increase your render time.

Cheers, cspear. I am using D3D and linear workflow (or trying to). I had IC set at 90 or 95 for the raytrace bit but never went above 50 for the IDL range as on a previous thread I was told not to as it led to light leakage and artifacts (the same problem I'm trying to fix). I'll have a crack with both maxed and see what happens. It might take a while!

Usng more IC ok, but you have to play with bounces too.

Hi Anthanasius. I should have posted a screen cap of the D3D render settings. I'll do that for the following renders as they come out (taking hours, as expected). Both of the images above were with 6 bounces in IDL and 2 in raytracing.

I've noticed this problem affects mainly smooth, uniform surfaces. I find that using the noise node to drive some bump - make the surface less even - can help.

The last-ditch cheat I use is to make the ambient color similar to diffuse, and set the amount very low: 0.01 - 0.025. In a normally lit scene it doesn't look at all odd, and can save having to crank render quality up.