Noise on particular areas

[joecharon]

Hi everyone, i am not able to identify source of strange noise in this scene.
I have tryed everything. No coplanar faces, removed all objects, changed
lights and materials subdivisions...
Notice that shadow is smooth on brick wall and on the pavement but grainy on white surfaces.
Rendered in VRay 2.50.01. I can send the scene to test.
Please help. It makes me mad as i can not produce final image.
Thanks!

Jozef

[joecharon]

Hi. Here is empty scene with passes.
The only light source is Vray Sun and Vray Sky.
Vray Sun has 16 shadow subdivisions. As you can see it works well on most surfaces exept white.
Global illumination pass is smooth. The noise is only in lighting pass and reflection pass.
SampleRate is OK too.
Now this is mystery to me...

Jozef

[Art48]

I dare to say that 16 subdivs is too low. Do you use a Gobo? What is your sampler clr thres. at?

Edit: And that SampleRate pass is definitely not okay. I really think that you either have a Gobo or some trees through which your light passes and casts soft shadows besides hard in the room. I'd raise the subdivs to 96 or 128 and see what happens.

[joecharon]

Thanks Art48. Yes there is 3d tree to cast shadow.
Here is image with 120 VraySun subdivisions + passes.
I have removed glass so that we can see objects behind it on the passes.
As you can see there is rough noise on bench even with so high settings...
Also sample rate pass has changed.

Jozef

[Art48]

1) Does your windows glass have some glossiness? 0.999 instead of 1.0? If so, 8 subdivs won't suffice.
2) Still, what is your clr threshold on the image sampler?. Best make a screenshot of your render settings. Also sample rate pass loks better now, although your floor doesnt have enough subdivs still.
3) Do you have any exposure corrections enabled int he VFB?
4) Try a clr threshold of 0.03 or lower and see if the problem persists.

[Macker]

the artifacts on the super-bright parts are caused by the antaliasing filter not being able to deal with such high numbers. If the pixel on the left has a value of say .8 and the pixel on the right has a value of 3, the average of those is still going to be 1.9, thus creating the sharp edges. Either use more subdivisions on the antialiasing filter OR clamp your output so that the highest value is 1

[Art48]

While you're generally right, I don't think its that issue in this case. Usually with straight lines the AA only produces regular jagged edges, and not "random sampling, sometimes top of the line, sometimes bottom of the line white dots" The jagged edges look totally like either very high color threshold or sick exposure correction int he VFB (since VRay samples less because its dark there for the renderer, but exposure cranked up in the VFB)

[vlado]

Would be best to get us a scene to support@chaosgroup.com - our support guys will be able to check what might be wrong.

Best regards,
Vlado

[joecharon]

Thanks guys, i use area AA filter and never had a problem with it. I don`t use exposure correction in VFB.
I will pack the scene and send it to support. Thanks Vlado.

Jozef

[Art48]

And by the way, if you really want help in the forum from other users you should at least answer all their questions

[joecharon]

Sorry for my impertinence. Had a realy hard day and was not able to answer all the questions.

[Art48]

No need to be sorry We all know how it is.