Rad/GI probs?

[Slick Systems]

Well we've all seen it before haven't we?

You get the scene how you want - then you spend ages getting it just right - then you hit that nasty problem that just wont go away!! :-(

Blobbies!!!!

Check out the attached file - I'm struggling to eliminate the lighter circular blobs on the end of the seat, I'm not sure what's causing it. Can't seem to get the edges smooth either - AA is on 4 at the mo.

I also seem to be suffering from some other blobbiness on the top of the seat but I'm hoping that sorting these out will cure the top as well.

Any help would be greatly appreciated as we all know these things are a nuisance to remove and can take ages to fiddle them out. I have tried playing around a bit but with no success. Strangely I turned off the behind test and they went away but brought out huge glare artefacts at the base of the seat legs where they touch the floor. (so no good there then.)

Here's the settings:

GI Final Gather Interpolated
Blur BK checked
Behind Test on
Intensity 550
Indirect Rays 7
RPE 550
SBR 20
AT 24.9
MPS 1 and 100%
Multiplier 100%

AA - 4
AS on
Thres .01
OS .2

Ray Recursion 12
Ray precision 6
Ray Cutoff .01


Regards LD.

[Tobian]

2 things I would suggest:

1) Use interpolated Montecarlo, with the same settings. The render time will be a little more, but it's better at not making such noise.

2) what is your lighting setup: Is that a large environment shining through windows above, with a light/sun coming down too? You might want to look at using Pom's 'exit portal' light for your windows, which should mean more photons get to where they should be in the scene.

I am guessing you're using 9.5.x, from the settings...

[Slick Systems]

Hi Tobian,

Very simple setup for this:

Area light,
Sunspot modifier.
No environment.

LW UB 9.5.1 1511Build

Will check out Pom's exit portal and try your suggestion about Monte.

BTW: love the surfacing tips on Meshpigs' thread - spatula was cool. If only I had that knowlegde :-).

Regards
LD.

[Tobian]

Haha, I am only slightly ahead of the curve, and I had to experiment myself to get it right too :D

Good luck with those settings. I just read that recently a lot of people were having issues with blotchies in internal scenes, with FG, so people suggested MC instead.

[Slick Systems]

Here's a new render with Monte on, still hasn't removed them.

I'm almost thinking this could be a surfacing problem? What do you think?

Have attached surface for endcap Node tree - trying to get a thick plastic look I'm probably using the wrong shader but it seemed to suggest that it would work for this type of surface, its the type of plastic thats slightly reflective, shiny, but has a kind of translucency to it which differs according to the thickness of the material - eg thinner lets more light show through.

As you can see I'm not good at description :-) hopefully you get the idea.

Regards
LD.

[Tobian]

Hmm yeah those circles are way too neat for radiosity blotchies, it's likelly to be transmitted light, through the material.

Firstly try it without, see if that solves your issues, if it does you at least know what's causing it.

I would say you're using the right shader, but you might want to try one of the new SSS shaders in diffuse first, as I know those have a pre-pass to speed up rendering, then build up your plastic reflections and stuff from there. Problem with testing such materials is they eat render time!

[Slick Systems]

The render time on this shot was fairly quick luckily, 'bout 5 mins - the scene set is kindly borrowed from excepts website the simple rad room which looked nice. I just tarted it up a bit with a few texture maps for the floor.

Then I boosted the GI settings slightly to give a better look to the seat, since this is my first attempt at SSS surfacing (of any kind) I thought I'd just keep it simple. Since Except know their stuff I assumed that the scene would be honed to some degree for speed - which it is.

And it's producing a nice pleasing image - if I could just eliminate those blobs and smooth out the edges a bit more.

Will test your thoughts though.
Regards
LD.