What In The World Is Causing This?

[Michael J. Brown]

I have tried everything I know to elliminate these "noise" artifacts, but no dice. Here's my basic set-up.

 

Max 2008

Mental Ray

(2) Area Lights with Area shadows (sphere light-area shadows)

Photographic Exposure Control

Daylight System (originating from behind camera)

A&D (metal) materials

 

How can I get rid of these artifacts?

 

Thanks.

[mesht]

i get a lot of those effects in my renders too, esp when using metals and matte plastic mat. i'm not sure what's the cause, could be due to the Fast Interpolation settings?

[SandmanNinja]

In my experiments, I've found that a high value (greater than 2.5) of Initial Final Gather Density will increase your detail while introducing noise (I think it's trying to increase the detail in the surface of the texture and gets carried away).

I usually use a value of 3.

 

Use a bit of Interpolation to reduce any noise (Interpolate Over Num Final Gather Points). Higher values of Interpolate Over Num Final Gather Points do not add a lot of overhead to your render times and it tends to smooth out noise. Downside: it removes local detail.

1=very blotchy; 30= pretty good; 200=Very Smooth

 

Hope this helps.

I usually use 30 for test renders and 100 for renders towards the end of the project.

[Dave Buckley]

maybe increasing the glossy samples of the a&d material that gives you the problem would eliminate it, although this will increase your render times.

 

also if you are using max 08/09 which i believe you are if you are using p/graphic exposure, replace your area lights with sky portals, assign a blackbody shader to each sky portal and then they become area lights with kelvin temperature controls. from my experience the sky portals are a lot less noisy than standard area lights.

 

hope some of this helps or maybe i have misunderstood

[Justin Hunt]

Could be a few things

 

1) low glossie samples on the metal

2) Low samples on the area lights

3) Low image sampling

 

For each ofthose increase the samples. Also play with the fast interpolate settings. try increasing the neighbouhoor samples. Higher numbers produce soft/blurrier results, too high can cause blockyness.

 

Agree with the use of portal lights instead of area light, as they give more realistic reflections. Although with higher shadow samples can cause slower renders. Worth it though

 

Nice models by the way

 

jhv

[SandmanNinja]

Dave - good tip about the blackbody shader. I'll have to play with that sometime.

[Dave Buckley]

sandman: the blackbody shader is really useful when you want to eliminate that blue tint your interiors are given from a daylight/sky portal combination

 

set the scene up the same as you would normally for an interior with daylight and portal, then assign the b.body shader to the portal and change the kelvin to the same value that you have set for your white balance in your exposure control and voila you have a white room rather than and blue tinted one, or just play with the kelvin temp to get different coloured tints, comes in very handy when customers don't like the 'real world' blue tint that you get as standard.

 

(thanks to jeff.p for letting me see the light with that one)

[Michael J. Brown]

Thanks to everyone for the recommendations. I will try increasing area light and image samples first (tried increasing glossiness samples before, but did not eliminate all noise). I'm ust a bit hesitant to replace my area lights with sky portals, as the finished scene will be a brew/pub with exposed can lights doing 90% of the illumination.

 

Of course, if these other mods don't do the trick, I'll have to give it a try.

 

Thanks.

[kbotnen]

Can you post a wire? It might have something to do with to small faces? Not enough to sample from? Just something I vaguely remember from someone else.

 

-K-

[cferman]

Try turning off your physical sky and then matte the two images together. Having physical sky on in the environment usually always gives me spikes like that somewhere...

[Michael J. Brown]

... assign a blackbody shader to each sky portal and then they become area lights with kelvin temperature controls...

 

 

How do I get/find the blackbody shader? I did a search and found a tip on Autodesk's AREA site saying it is native to 3dsMax and directing me to the base.mi file to remove its "hidden" status by placing a # in front of the "hidden" within that file. But following those directions didn't change anything. The blackbody shader is still not available to me.

 

How can I access it?

 

Thanks.

[Michael J. Brown]

Try turning off your physical sky and then matte the two images together. Having physical sky on in the environment usually always gives me spikes like that somewhere...

 

 

I've tried deleting all lights (including daylight system) and still get artifacts. I've even saved all my objects to a new file - to completely bypass any side-effects of having had a daylight system in the scene, and still get the artifacts.

[Michael J. Brown]

Okay, by turning on Fast Interpolate for my materials I've been able to achieve the following result. Not 100% free of artifacts, but a heck of a lot better than before. Glossiness samples still set to default (8). I tried much higher (36), but didn't see any difference. Still using area lights with area shadows (couldn't assign blackbody shader to light portal). and have illiminated the Daylight.

[pixelperfectg]

Glossiness samples still set to default (8). I tried much higher (36), but didn't see any difference.

Hehehe, you think 36 samples is high? That can be a drop in the bucket when speaking of clean/glossy reflections.

 

I posted some info on A&D samples in my blog last year that you may find helpful:

http://jeffpatton.cgsociety.org/blog/archive/2007/4/

But it's mostly the same thing that's already been discussed here..except it has some pretty pictures with it..lol.

 

Something that hasn't been mentioned yet (that I saw) is the mia_envblur shader. If your objects are reflecting an HDR environment (kinda looks like may be), then you may want to see this post on Zap's blog:

http://mentalraytips.blogspot.com/2007/11/more-hidden-gems-miaenvblur-gloss.html

[Justin Hunt]

Just thought of something, are you using the brushed metal preset? If so remove the bump map or swap it out for something else.

 

jhv

[Michael J. Brown]

Hehehe, you think 36 samples is high? That can be a drop in the bucket when speaking of clean/glossy reflections.

 

Well, actually I did try 200, but the render time was too ridiculous for me to even continue the experiment.

 

 

I posted some info on A&D samples in my blog last year that you may find helpful:

http://jeffpatton.cgsociety.org/blog/archive/2007/4/

 

 

You mentioned using Interpolation to "balance the smoothness and render time". Which Interpolation were you refering to? The interpolation within the materials, the F.G. interpolation, or perhaps some other interpolation value?

 

-ALSO- Can someone please help me access this "blackbody" shader for use with the light portal?

 

Thanks.

[pixelperfectg]

Which Interpolation were you refering to? The interpolation within the materials, the F.G. interpolation, or perhaps some other interpolation value?

The A&D reflection interpolation option. BTW, you can click on those small thumbnail images for the larger image that shows the settings I'm referring to.

 

-ALSO- Can someone please help me access this "blackbody" shader for use with the light portal?

Oct. 20, 2007 blog entry:

http://jeffpatton.cgsociety.org/blog/archive/2007/10/

and

Dec. 24, 2007 blog entry:

http://jeffpatton.cgsociety.org/blog/archive/2007

[Michael J. Brown]

Thanks Jeff. But I'm still getting the same results, even with the same settings you're showing. There must be other variables at play here.

Edited May 7, 2008 by renderhaus

[Michael J. Brown]

Okay... One more question.

 

I've managed to get the blackbody shader applied to my light portal (which I am using as a single light source from my ceiling). But now Everything above the portals elevation is completely black. So instead of being able to see the corrugated metal deck above my steel joists, all I see is blackness. What gives? What do I need to adjust on the light portal allow the camera to see beyond it?

[Michael J. Brown]

3rd time's a charm...

 

I changed my areas to points and took the mr Physical Sky out of use in the background Environment Map (left over after Daylight deleted).

[SandmanNinja]

VERY NICE!

 

Glad you got the noise sorted - nice image.

[Michael J. Brown]

Thanks, Sandman. Unfortunately this particular piece of brew equipment won't even be seen in the final render - that is unless I can convince the developer to pay me for a second shot from the opposite end of the pub. But this let me perfect the material for application to the other brew equipment closer to the foreground of the final shot.

[shaneis]

...I changed my areas to points and took the mr Physical Sky out of use in the background Environment Map (left over after Daylight deleted).

 

Then Spock-logic suggests the only possible cause is your area lights. Sorry to chime in late, but your problem is most probably because you were using spherical area lights. They "dilute" the samples around the whole scene but by replacing them with disc area lights and setting your high/low samples just right, you're aiming all that sampling info where you want it - on the subject. I often find with problematic area lights that a low sample value of half the high sample value will fix the problems (for eg, try highSamples=64, lowSamples=16/24/32 until your specular smoothes). Not sure about Max options, but in Maya the area light has theses sample channels, highSamples, highSampleLimit, lowSamples. If the highSampleLimit=1, then once the light has "hit" once, it will revert to the lowSamples value, so increasing the lowSample value will retain the quality. On a similar note, if you're using a procedural map for the A&D's reflectivity to generate the brushed effect, filtering the map can also help as the map is what's providing the info that governs how the area light will reflect back to the camera (ie specular info).

 

S.

Edited May 8, 2008 by shaneis