Lots of speckle in vray2 scenes

[squeakybadger]

Hi all,

We are using our standard material/modelling process that has worked fine in vray 1.5, but on the switch to 2.0, we are noticing a lot more white speckling on the materials.

Tried all the usual tricks of invisible lights/more subdivs/sub-pixel mapping, but nothing seems to shift them any more.

Anyone seen anything like this or know how to fix it. Attached a quick render with the problem areas.

Cheers for any help.

[vlado]

Do you have the "clamp output" option in the color mapping section enabled? If yes, then this is probably why. You can either disable it, or else email me to vlado@chaosgroup.com for the fix (it will also go into the next official update somewhere at the start of February).

Best regards,
Vlado

[squeakybadger]

Hi Vlado,

Disabling the clamp didn't seem to do anything.

I have sent you an email about getting the fix if we can try it.

Thanks!

Jaime

[vlado]

Hm, thanks for the scene, but I get the exact same result with V-Ray 1.5 SP5, see the attachments.

Best regards,
Vlado

[tricky]

I am getting speckle on some of my materials, though I don't really know if it is down to vray2 alone. We used to get these problems very occasionally with 1.5 too. Basically, if you tell the vraysun to be invisible, the speckles go away. The problem is that I really want the sun to be visible as it affects the quality of my textures generally from certain camera angles (i.e. getting a nice specular reflection of the sun is a good thing) - I just don't want the 'pixel speckles'. How do I resolve this?

[vlado]

It really depends on what causes the speckles. Usually they are generated by reflections of reflections of the sun (or reflections of the highlights from the sun) and if this is the case, it may be hard to get rid of them. You may be able to use a VRayOverrideMtl material to use a slightly more diffuse version of a material for reflections (not the material on which the speckles are visible, but the material that causes the sun to reflect and cause the speckles).

Best regards,
Vlado

[Morbid Angel]

it looks to me like its not a speckle but rather a really glossy reflection with not enough samples. What would happen if you give the shader 64 samples in the reflection and improve your dmc sampler quality?

[vlado]

More samples will certainly fix it, but of course, for higher render times...

Best regards,
Vlado

[tricky]

it looks to me like its not a speckle but rather a really glossy reflection with not enough samples. What would happen if you give the shader 64 samples in the reflection and improve your dmc sampler quality?

I will give this a try, but it is only certain materials that are affected, so it would be frustrating to improve the DMC sampler quality. This is a HD animation, so render times are even more critical.

[tricky]

It really depends on what causes the speckles. Usually they are generated by reflections of reflections of the sun (or reflections of the highlights from the sun) and if this is the case, it may be hard to get rid of them. You may be able to use a VRayOverrideMtl material to use a slightly more diffuse version of a material for reflections (not the material on which the speckles are visible, but the material that causes the sun to reflect and cause the speckles).

Best regards,
Vlado

So it could be, for example, my window glass reflecting reflections of the sun onto my paving material (where the speckles are)? Can I tell just the glass of the windows not to reflect the sun in that case?

[tricky]

I seem to have pinned the problem down to the reflectivity of the glass in my scene.

If I set reflection of the glass to black, I get no speckles (but then the glass has no reflection so it looks rubbish).
If I set the reflection of the glass to near white (240,240,240), I get speckles.

How do I solve this?

[pixela]

Can you use VrayOverride material?
So the reflecting material will have very little reflection or black reflection value.
Then the reflection of reflection will not be visible on the speckled area.

[tricky]

Can you use VrayOverride material?
So the reflecting material will have very little reflection or black reflection value.
Then the reflection of reflection will not be visible on the speckled area.

I could give that a try. Will report back.

[tricky]

That seems to have done the trick. Thanks pixela.

It would be good if there was a more general solution to this problem though. Sometimes it is difficult to know which is the problematic material, and sometimes you might actually want it to reflect the sun onto other objects. I'm not using any GI in this scene - just the vray sky, sun and a vrayambient light.

[pixela]

Yes I agree.
I am not sure but I think these kind of problems mostly appear because the reflecting reflection has a very high float number. There are anti-aliasing issues with DMC Sampler in the very bright areas in my renders and sometimes problem continues even with the clamp output and sub-pixel mapping. I think this is a similar case for reflection of reflections too.

I also wish that there is another solution for such problems.