Render artefacts

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Old 01 January 2013   #1
Render artefacts

I've been following a modeling tutorial (Swiss knife modeling). Did a final render. And got some strange artefacts (see them outlined). Can anyone tell me how can I get rid of those? (My render settings are quite high; including antialiasing and things).

Thank you in advance.

"Open image in a new Tab/Window" to see the full-size image (I guess):

 
Old 01 January 2013   #2
Could you be a bit more specific about your render settings?
 
Old 01 January 2013   #3
Try playing with the filters in the AA settings, or dropping the threshold.

cheers
brasc
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Old 01 January 2013   #4
Could also be reflections from the saw blade.
If you red dot the render for that blade it may clear that up
as the rest of the reflections look uniform.

HTH
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Old 01 January 2013   #5
Im mostly certain you would need to lower the AA threshold. Lower it from 10 down to 5% and see if that helps.

Also on a physical note, the fingernail tab on the large blade looks a bit small to be able to pull the blade out.
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Old 01 January 2013   #6
Ok, my AA threshold really was at 10. Now it's 5. Same result:



Threshold = 5


Threshold = 1


What else could it be?

P.S.: thank you for the physical note. Will tweak it.

Last edited by Bhangra : 01 January 2013 at 07:34 PM.
 
Old 01 January 2013   #7
If not reflections ... perhaps your geometry for that blade ?
-check poly direction, etc.
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iMac 3.06 ghz Intel Core 2 Duo / 16 GB / OS 10.9.5 / C4D StudioR12 / CS6

R.I.P. 11.02.11 ... my dear friend .
 
Old 01 January 2013   #8
Try reducing the Reflection/Ray Depth it looks like it's bouncing around a lot in metal areas.
If not try some AA filters as I mentioned above.

cheers
brasc
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Old 01 January 2013   #9
Quote:
Originally Posted by vid2k2
If not reflections ... perhaps your geometry for that blade ?
-check poly direction, etc.


Geometry is seemingly ok. An now... same problem different place:

 
Old 01 January 2013   #10
Quote:
Originally Posted by brasco
Try reducing the Reflection/Ray Depth it looks like it's bouncing around a lot in metal areas.
If not try some AA filters as I mentioned above.

cheers
brasc


Reducing R+R Depth kinda works, thank you. (The result is far from being "tasty" anyway.):

Big image opens in a new window:


And here are the settings:
 
Old 01 January 2013   #11
seems to me the 1% while still problematic shows several areas much better than the 5% so I would go back to that. Second, 1x1, 4x4 is low, very low so threshold wasn't even the biggest concern you'll need to go higher.

Try turning on the clip negative component although not really an issue with cubic, but cubic may be part of the problem, try sinc or Mitchel
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Old 01 January 2013   #12
I think that is the magnifying glass in the reflection, the surround color { of the glass } is just to close to that, in the reflection.


Try adding a different material, say green to the white surround, then see if your artifact is now green.
 
Old 01 January 2013   #13
you should read the manual, this exact problem is there described under min/max/hreshold.
the threshold defines the tolerance in color/brightness variation before a new subsampling
level is applied. when these problems occur - very small jagged lines (1-5 pixel width) it
basically means your maximum stepszize is to low. these problems oftens occur for highly
reflective or refractive surfaces on areas with very sharp eges (drastic changes of the
surface normal).

for such areas raising the threshold won't help, as the sampling is already at max level at
these points (areas of very high contrast, the brightness almost jumps from 0 to 100 with
one pixel. there are not enough subsamples to solve the incoming samples there. lowering
the threshold beyond 5% does only make sense when you have very subtle brightness
changes in you image and you want to sharpen them. a chorme reflection is the opposite
of that.

for a perfect render you would have to go for something like min 4* max16 @ 10-20% i
guess. but i personally would prefer to fix those edges in ps rather than spending 50%
to 200% more render time for such small areas.

happy rendering,
ferdinand
 
Old 01 January 2013   #14
Quote:
Originally Posted by Little_Devil
for a perfect render you would have to go for something like min 4* max16 @ 10-20% i
guess. but i personally would prefer to fix those edges in ps rather than spending 50%
to 200% more render time for such small areas.


You should almost never raise the minimum AA size past the default of 1x1. Always go for lowering the threshold first (Dont go much past 3%) the maximum AA second (8x8 should be fine for any scene) and as an absolute last resort the minimum AA last. Ive never come across any scene; mine or someone else's that im fixing; that needs more than 1x1 minimum.
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www.3dfluff.com
 
Old 01 January 2013   #15
Thank you all guys. Here is the final render:

No artefacts here
 
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