The picture I have in production is of someone looking out of a window. I have a backdrop outside and a IDL-Dome. The room is totally closed in. I use one point light outside, and it lights

the scene beautifully.

The lights in the scene (Using IDL) works a treat with amazing depth

I have had two problems, one of which I have solved:

1. almost clowdy, splotchy swhadows on the inside of the window, which is lit only by indirect light, reflecting from the room

2. a series of dark spots on the inside corner where the window and the frame meets. Much like if the frame was moldy

The picture illustrates the problem

I had an extended look at the r'osity fora, and found some nice explanation and settings from Bagginsbill (who's surprised?), which reduced, but did not remove the problem.

Then I actually had a thorough look through the manual (it's a stretch, I know...). There I found the recommendation to reduce the irradiance caching to zero and increasing the Indirect light quality to a correspondingly higher level.

I also reduced the min. shading level to 0.11 and increased the pixel samples to 6

This worked a treat, and I now got picture three.

First problem seems to be greatly reduced, but it is not quite gone.

And the second problem remains. It actually reminds me of something, which often happened when using AO. SO i attacked the texture first of all. Replaced the current texture, which is by Ajax, with a simple white. No change

Then I upped the shadow samples to 30 and reduced the bias to 0.1 for my light. No change

Then I tried to switch off smooth polygons, just in case. No change.

Finally I thought that the spots might be smaller at a larger scale. So I parented the whole show to the IDL-dome and resized that to 10000. No change.

I am not sure what to do now.

Would anyone have had the same problems and some brilliant solution?

If I'm not all mistaken, I think this was discussed a few times already, with the result, that there is no solution yet, for getting rid of these dark blotches (in combination with IDL enabled)

It gets even worse, when trying to illuminate a closed room with just light emitters ("glowing objects"). ... Well, on my end at least =)

Thanks Erick

Not much optimism, but there we are....

....unless something else emerges.

Try turning up IDL quality all the way to 100. And put the shading rate back to 0.2.

gray, try it with IDL IC = 100. in technical terms, this means that GIMaxError = 0 (no interpolation) in FFRender.  GIVariables are used in FFRender to calculate IDL bounces.  use d3d's Render Firefly script in scripts/partners menu.  there are two IC variables.  first: ordinary raytrace IC, which can be set as in above render settings screen.  second: IDL IC.  when IDL is enabled, raytrace IC value is ignored by FFRender.

blotchy artifacts may also be seen where transparent/refractive posersurface contacts another posersurface, e.g. windowpane touching frame.  bill discussed contact artifacts, along with corner blotches.  possible solution: micro-bevelled corner, in case anybody wants to modify one of these poser models.  nobody has tried it yet AFAIK, as they may feel it's too much work and they might lose the UVMapping.

Corner blotches happen on any surfaces touching at 90 degrees, not just transparent/refractive.

Thanks to all of you.

I have a render on the way on the lines of Miss Nancy's proposal. Very sloooow ;-)

BB - does that mean that it is, as ErickL88 says, unaqvoidable and to be dealt with only through postwork (as I have been used to do the the AO blotches)??

(and by the way thank you for the glass shader I am using, it is simple and brilliant!)

in re: "contact artifacts":  two surfaces are parallel, not orthogonal.  poser glass within some small distance from some opaque posersurface, close enough so that it appears to be touching.

p.s. stefan made the same suggestion as mine, but I crossposted.

My suggestion is not the same as Miss Nancy's. I'm suggesting to increase the IDL quality, not the irradiance caching. Cranking up irradiance caching will only shring the size of the splotches but not change their appearance.

OK here is the status:

I rendered the picture with the IDL irradiance cache of 75 as per Miss Nancys proposal. I tried 100, but that was painfully slow (maybe two lines of rendered buckets in an overnight render)

But the higher irradiance cache did quite a lot to remedy the problem.

I got a little clouding of the faces of the window frame, since the higher IC makes blotches more visible.

But I think this is a reasonable compromise

http://www.renderosity.com/mod/gallery/index.php?image_id=2318372

Thank you all for your swift and knowledgeable assistance!

Here's a cheat that will improve but not eliminate the problem:

In the material room, find the surfaces that exhibit the artifacts; plug the color map into the ambient color node (NB as well as, not instead of the diffuse node) and set the ambient color to white.

Make the Ambient Value very low - something like 0.02 for starters - and do a test. Raise / lower the ambient value until the artifacts are minimised but the wall (or whatever) doesn't look like it's glowing. It's a very fine balancing act, but it saves having to hike up the IDL quality and produce long render times.

does IDL bounce rays? 

maybe it's cuz the smaller object is bouncing to an object with more area to cover and therefore the rays can't give similar coverage to the larger object.  or does the outward traveling ray expand to proportionately larger area?

slopey pixels?

y=mx+b or (y2 - y1)/(x2 - x1)  ?   or maybe it's trying to divide by zero?   headscr'ch

yes, lara, FFRender calculates diffuse bounces, hence it takes time, as they tend to bounce an incoming ray in many directions, and they tend to lose intensity with each bounce.  anyway, that last render by gray looks pretty good.

Thank you again for your assistance, all of you.

I might try your cheat next time, cspear...

Thank you, Miss N for the comment on the picture.