Cleanup noise in Elements: Reflection and Shadow - Also LOOONG render times

[CEDRIC_JACCHERI]

ok thanks for your response

[zeronove]

Hi Svetlozar,

finally I've converted your scene for my 2011, but now I've a lot of questions for you ...actually about IM/LC that is my usual

workflow ...so, lets move on, following the tabs order:

IMAGE SAMPLER

min/max values are clear, what about subpixel mapping and LWF checkbox?

- I know that subpixel mapping is faster but someway wrong because it returns often darken images and it kills highlights; as first

choice I usually go without it but I admit it's not so clear in my mind.

- I never use the lwf checkbox; in my understanding is a sort of fast way to convert a no-lwf scene to lwf; I could imagine you use it only to avoid

manual materialcolor adjustment, correct?

IRRADIANCE MAP

- Pretty high and sensitive custom settings for that resolution, any comments about it? Usually my settings are lower than these, could it be this one a reason of my

difficulties to solve noise without high AA and mtl/lights subds?

LIGHT CACHE

- I've never thought to unchecked "store direct light" when LC is use as secondary engine; is this specific to this sample scene or is

it recommended even in a real scene that usually comes out with a lot of lights?

- Filter settings to none: is this recommended? I remember from helpfile that it's only for testing purpose, am I wrong?

DMC

- What's the purpose of the increased value for the min samples?

MATERIALS

-I admit I've never understood well how material interpolation works; I see that values are equal to IM except for normals, is this

the raccomended way to go? Maybe, on the basis of yours fast rendertimes, could be better for me to look at this old feature very closely.

LIGHTS

- What's the purpose of the ambient light? I've never thought about this kind of "hybrid" use; what's the general idea behind it?

ELEMENTS

- I see you use both normal elements than raw elements, I know the difference for compositing but what about checking noise?

- Please, look at the samplerate element attached, could it be considered a good sampling?


PS sorry Morne, if you feel I'm hijacking your thread, I can open a new one, just let me know.

[Morne]

PS sorry Morne, if you fell I'm hijacking your thread, I can open a new one, just let me know.

No It's fine. Your questions are also valid and related to this thread. I think it will be good to keep it all in 1 place.

[svetlozar.draganov]

First of all I want to inform you that the settings in my scene are not perfect - the main work I did is to clear the noise - not to test what is best for the scene.
Now I'll try to make some fast test on some settings and to answer you what works better !

1.Subpixel Mapping - if this parameter is ON it creates more sharp transition between dark/bright pixels - in this situation it works better if it is OFF the transition between walls and the background is smoother.

2.LWF and Gamma - (this is usually very LONG theme) - the best way to work with LWF at the moment is to use Linear Workflow ON and Gamma - 2.2 from Vray Color Mapping Rollout and to disable 3DSMax Gamma. Most of the users are using 3DSMax Gamma but there is one great disadvantage to that - the colors in viewport, material editor and rendered image do not match - no matter if you set "Affect Color Selectors / Material Editor" the problem is still there. Vray Gamma doesn't have that issue - it is just better.
One questions is always asked when I talk about this setup - Why in the help file is written that this workflow is not correct - it is just because there is a tiny difference between Gamma and sRGB curve. Vray Gamma Setup and the 3DSMax Gamma setup are not 100% correct LWF just because Gamma curve is different that sRGB curve - the difference is very very small. At the end Vray and 3DSMax LWF setups will produce the same result - but with Vray setup it would be easier to work with!

3.Irradiance Map - I set this settings a little bit high because the lighting in this scene is a bit difficult to calculate. In general I usually set higher settings for indoor renderings especially when there is not much openings. This will guarantee that GI will be smoother and it will bring light to difficult areas. In this scene I think it would work fine and with default High Preset. I don't know what settings are you using - but Irradiance Map lower settings usually produce splotches not noise.

4.Light Cache - Store Direct Light - in this scene it should be better to be turned ON - it should produce smoother lighting and it would save some time. I did some tests but don't see any difference. I usually turn OFF this parameter if I work with a couple of lights in the scene - and turn it ON if I have many lights.

5.Light Cache - Filter Settings - In my personal opinion when Irradiance Map is used with good settings like High Preset - it is better to turn off any filter in LC. By default LC produce very smooth lighting and a lot of details and edges are lost and when filtering is ON they are blurred even more. When IM is your primary bounce LC is baked into it and IM works as a filter for LC.

6.Image Sampler Min Subdivisions - in some noisier scenes which noise is difficult to remove leaving Min Subdivision to 1 doesn't work well for me. Sometimes I decrease Color Threshold a lot but for some reason Image Sampler doesn't place more samples on some areas with noise - because of this I prefer to force manually Image Sampler to use Min Subdivision to 2 or 3 and to keep Color Threshold not very low.

7. Material Interpolation - this is one of my favorite features in Vray - especially for Glossy Reflections with value below 0.75. I have always use it if I have large elements in my scene like walls/floors/ceilings etc with lower glossiness- it will speed up your rendering a LOT and it will clear the noise very well - it works fantastic. The downside of this as every interpolation in Vray is it could not be used in animations - but for stills is just the best. This is actually Irradiance Map Interpolation and the settings are just the same as Irradiance Map Settings.
In Reflection Interpolation Settings there are - Min/Max Rate , Interp.Samples , Color and Normal Threshold - what is missing here is Hemispherical Subdivisions and this parameter is Refl.Subdivisions.
Tweaking this parameters is just like tweaking Irradiance Map but one general rule is important: Don't enter Min/Max rates in Interpolation lower/higher than Min/Max Rate in Irradiance Map.

In other words let say you have IM with Min rate = -3 Max rate = 0 for Reflection Interpolation don't enter values below -3 for Min rate and above 0 for Max rate - otherwise when you hit render IM will calculate extra passes. For example if IM Min rate = -1 and Max rate = 0 - you will expect to calculate two passes - but if you have materials with Min rate -3 Max rate 0 - then the passes will be four. Try to fit Interpolation rates into IM rates!
When I tweak Interpolations I usually start with default values - if the result is too smooth or floating I increase Max Rate and decreate Min rate and increase Hemispherical Subdivision which here is Reflection Subdivisions.

8.Lights - Ambient Light - the reason for this light to be there is because difficult lighting. I don't really like the lighting in this scene at the beginning. At the area of the opening everything was just burned out on the other side the flash light was too strong too - and in the middle of the hall it was dark. What I wanted is to create smoother lighting in the whole room - from one side to the other without burned areas and dark effect in the middle. I created Light Portal in the opening but it still didn't get me the smoothness I wanted- it was still dark in the middle and when I increased the flash light and the camera exposure in the middle was fine but in the ends was too strong. That's why I decided to add minimum lighting to all objects in the scene with ambient light and this helped me to create better lighting - this also helped to Global Illumination and noise solving.

9.Render Elements - Noise checking - The only reason to add Raw and not-Raw Render Element is just because the noise is more visible in Raw RE - and it is easy for me to notice the changes when I tweak some parameter - I also pay attention to not-Raw RE and Beauty-Pass. You should remember that it is a waste of time to try to clean perfectly Raw-RE, at some point this noise is not visible at all in Beauty Pass.

10. SampleRate Element - your SampleRate Element looks good and the noise levels are really low for this 16 min render time.Is this with Interpolation ON or OFF? SampleRate is just a feedback of how much adaptive is Adaptive DMC Sampler. Adaptive mean to have less samples in easier areas , and more samples in difficult areas of your render. If for example the whole SamleRate is red this means that Image Sampler use only Maximum Samples - in this situation is better to switch to Fixed Image Sampler - because Vray will automatically use the amount of samples you've set and it doesn't create calculations for - how much samples should I use.

Regards
Svetlozar Draganov

[cecofuli]

Ok, a lots of infos here, but with "morbid setting" or also US, there is a big problem: strong reflection on reflective material with Sub-pixel OFF - Clamp OFF - Don't affect color OFF. In my real project (you can see in attachment) for the little square region render, (LWF with 3ds max gamma 2.2 - Affect Color and Affect Material ON - Input Gamma 2.2 - Output Gamma 2.0 - Reinhard 1 - 0.3 - 2.2 - Buckets size 8px) with Sub pixel on the rendering time is 30 second. Ok, perfect! But, with sub-pixel OFF = 7 minutes! Yes! 7 minutes for 30 x 40 px region rendering!!! So, something is wrong in our methods...

[Morbid Angel]

did you use light cache for glossy rays?

[cecofuli]

Yes Morbid Angel! And we have a very, very high rendering time (>30 min for a single 32 bucket size) in the same file with a series of bottles of glass. You can see this models in the previous crop render (not very well ^__^ )

[svetlozar.draganov]

Could you please send us an example of this scene - and we will try to help you with this issue?

[cecofuli]

Ok, I clean up a little the files

[Morbid Angel]

Ok, I clean up a little the files

yeah i'd like to have a look also...

[vlado]

Me too

Best regards,
Vlado

[cecofuli]

Ok, here the files. Click render.
Very simple files =) And I had the same problem, to rendering a lot of bottles of glass, with this scene (US and sub-pixel OFF etc.. etc... ). Rendering time, over the glass, was very huge(hours for buckets)!
And the shaders are nothing to special...





EDI: I render the file in attachment, with the default settings and the cropped rendering area: 57 min with esacore I7 4.0 Ghz... Too much I think. Most of the time the buckets are on top of the big bottles of glass, glasses and crome chairs...

[cecofuli]

(*) I simplified the two big bottle (red and blue) shaders (Glass and the bung). But the buckets stay a lot of time on the left glasses. Now the render time 20-25 minutes.
(*) I remove the "Reflect on back side" for the glasses shader. Now the rendering time is 14-17 minutes. Here the new file.
(*) As we know, If I enable Sub-Pixel mapping, the rendering time is 1 minute. Yes, ONE minute. But, obviously, I want it OFF. In this scene we have x15 times. Mmm... Too much difference in rendering time/result.

[Morbid Angel]

well it seems that the ies lights is what creates such a long render time. I think the really long reflection/refraction time can be related to the ies also. Lastly I think the curtain as is also triples the render time, based on my simple test from 45 seconds without the curtain with grey override, to 3 minutes with the curtain (no ies lights).

[cecofuli]

So, for you Morbid, with the simplified Glass shader (glasses and bottles) and VRaylight plane instead IES lights, there are nothing to do? And, for the x15 with or without Sub-pixel? When the buckets are on the chrome chairs the rendering time is huge compared with Sub pixel ON (but not only with the chairs, in all the scene) . The curtain shader are very simple (VRay2Side with some little maps inside for Opacity, reflect etc...) So there nothing to optimize, I think.