Noise in render from cards

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Old 07 July 2013   #1
Noise in render from cards

Hi all, I'm not really too sure as to why this happens but I get noise all over this geometry when I render. I know for a fact it's caused by these cards I have in my scene that I'm using for certain reflections and specs. This happens to all objects that have a bump..
Attached Images
File Type: jpg Render.jpg (83.3 KB, 28 views)

Last edited by Argiri : 07 July 2013 at 08:06 PM.
Old 07 July 2013   #2
there is a number of things that could be causing that. may need more info from you though.
are these bounce cards? or are they geometry for like, playing cards?

if the bump is off does the noise disappear?
what kind of lights are you using?
are there low glossiness values in the shaders for those objects?
are you using final gather/global illumination?

different shapes and patterns of noise can be distinguished visually to determine the source of the problem. so it is hard to tell what is wrong by simply saying "noise"

too noisey of a bump channel causes noise, shadow samples being low causes noise, low FG or GI accuracy causes noise, low glossy samples cause noise. :P
Old 07 July 2013   #3

I have uploaded a couple of images, I took out the cards that are giving the jar the main highlight ( yes the cards are being used for bounce lights), but I still have two more cards ( you can see them in the reflection of the jar). The render settings are also there. I had a similar issue on the seed but somehow it magically resolved itself when I reopened the file.
Thank you
Attached Images
File Type: jpg Render_Settings_2.jpg (81.7 KB, 6 views)
File Type: jpg Glass_wo_cards.jpg (78.7 KB, 17 views)
File Type: jpg Render_hd.jpg (86.9 KB, 20 views)

Last edited by Argiri : 07 July 2013 at 08:04 PM.
Old 07 July 2013   #4
This looks like the same effect when you overdrive an area lights' visibility. My guess would be that your bounce cards are... too bright? Are they emitting light as well as reflecting it?
Commodore 64 @ 1MHz
1541 Floppy Drive

"Like stone we battle the wind... Beat down and strangle the rains..."
Old 07 July 2013   #5
Infernal, yeah they would be emitting light since FG is on.

and now that i see the render and recognize it. hello! I know you. :P

looking at the the image the two things that come to mind are multipixel filtering artifacts and glossy artifacts.

what are the samples on the glass jar set to for it's glossiness?

make sure the gauss filter values are set to default not 2.33

if that doesnt work.. what you might try to do is slap a simple camera lens on to the render cam and set the gamma to 1. it tends to avoid highlight burns like that. though it is kind of a forceful thing.
Old 07 July 2013   #6
This is a known issue that has been around for ages, there may be 2 solution:

-Try to simply add a mia_photographic lens shader (with a 2.2 gamma), this might clamp the super bright grainy artifacts (try both in render view and 32 bit batch render).

-Lower all the light sources intensities (specially your cards) and compensate with the lens ISO knob.
Old 07 July 2013   #7
I actually had this come up on some wood cabinetry in a recent kitchen scene. I was using mental ray Area Lights as light cards, with a shape intensity at 5. Once I turned off the visibility and used background image-textured planes, the issue disappeared entirely. So I think it has to do directly with a light being overdriven, breaking the (so-called) physical accuracy of the shader.

Given recent physics news dethroning Maxwell and co., you just have to get a kick out of the standard lighting model altogether. It's no wonder that the people who program the rendering engines have a rough time, but that's another story entirely!
Commodore 64 @ 1MHz
1541 Floppy Drive

"Like stone we battle the wind... Beat down and strangle the rains..."
Old 07 July 2013   #8
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