Strange noise in render element

[mattmarshall]

Hi Forum,

 

Im getting noise in my shadow and reflection render elements. Wondering if anyone knows how to fix it?

 

Ive attached the RGB, RawReflect and an ID pass to try and show whats going on.

 

Standard box mapping on all objects. Using dome with HDRI, GI settings are high and no noise on RawGI passes etc. Light subdivs are high. Material subdivs are high.

 

Help,

 

Thanks

[laurynasdvareckas]

I would get similar results if there are duplicate polygons.

[mattmarshall]

I would get similar results if there are duplicate polygons.

 

Thats a good idea but just checked and its not the case unfortuantly

 

Thanks

[Larissa Holderness]

I get these same issues as well. Even in remodeled glass. No idea why.

[Chris MacDonald]

Your RGB is more or less noise free. Don't sweat the noise in the passes - it is like that because VRay spends less time sampling areas that it deems "clean enough" - which, if you look at the RGB pass, they are. If it were to sample those areas as much as it samples the "clean" areas, your render times would be through the roof.

 

If you look at the base of your column where that noise is - there are almost ZERO reflections in the RGB pass - so VRay has decided that there is no point in further taking samples at that point. If you made that column more reflective then you would notice that the noise in the reflection pass would decrease as the reflections are more visible.

 

"V-Ray is an adaptive sampling engine. This means that whenever V-Ray needs to compute a value, like the color of a pixel, or the light reflected from a surface, V-Ray will take a varying number of samples for that value, depending on the context. The adaptive algorithm that V-Ray uses is very straightforward: for any effect that requires several samples, V-Ray first computes a small amount of samples, and then, if the variance of the samples is too big, it continues to take more samples until the result is good enough.

 

The samples that V-Ray needs to compute can be broadly classified as image samples and shading samples. Image samples are those directly related to pixel values that compose the final image, including depth of field and motion blur effects. Shading samples are those taken to compute effects like glossy reflections, global illumination, area lights etc. V-Ray employs adaptive sampling in both of these cases."

[mattmarshall]

Your RGB is more or less noise free. Don't sweat the noise in the passes - it is like that because VRay spends less time sampling areas that it deems "clean enough" - which, if you look at the RGB pass, they are. If it were to sample those areas as much as it samples the "clean" areas, your render times would be through the roof.

 

If you look at the base of your column where that noise is - there are almost ZERO reflections in the RGB pass - so VRay has decided that there is no point in further taking samples at that point. If you made that column more reflective then you would notice that the noise in the reflection pass would decrease as the reflections are more visible.

 

Hi Chris,

 

Thanks for your reply, that makes sense.

 

I really need my reflection pass for a complex backplate that im going to be using in PS. Render times are already up there so I guess il have to suck it up and find a different way.

 

Thanks

[Chris MacDonald]

You can force VRay to sample this more by lowering the noise threshold in the Global DMC rollout. (I think) and/or increasing the minimum samples in the DMC.

[Tom Sproule]

There are two options you have.

 

You can raise the samples of the HDRI through Vray Light Lister. I know the lighting samples are supposed to be controlled by the 'Bucket image sampler' rollout and/or 'Global DMC' rollout, with the Noise threshold amounts. However, HDRIs for some reason also need the subdivs raised independently. If you don't you can get noise as well as splotches in your render.

 

Second you can go to the 'Image Sampler (Anti Aliasing)' and raise the 'min shading rate' and that should also reduce noise - try 32 or 64 or whatever you like.

 

Those are the two solutions I can think of. Hope they help.

[h3d]

Matt

 

Would love to know if either Chris or Toms suggestions worked for you. Hope one of them did!

[Francisco Penaloza]

To me that's the reflection of the same object on it self, so VRay is trying to sample that reflection and that need more samples or lower noise threshold.

As mentioned by Chris it should not affect your comp as long your beauty pass looks clean, if you are trying to increase the reflection on that column then you need to lower you noise threshold or increase the samples of that object on the VRay object properties. This multiplier works with the general Min Shading rate so you need to adjust accordingly.

If your scene has mostly simple flat object ( not grass type of object) then you can increase your minimum shade rate at the same time you increase your over all Antialising and lower your noise threshold.

[stannickkhon]

Hi

[mattcooper]

I'm pretty sure that your Reflection Pass will be clean, Raw passes are usually noisy, and in Comp you'd need to multiply the RawReflection by the Reflection to get the final Pass so it should all be fine and clean. Have you done this?