blotches and artifacts in final render

[philvanderloo]

I found that increasing subdivs in irradiance map minimizes blotches, (see left side of attachment), but still pretty blotchy.

Given I have all of my final render settings almost dialed in and the render is taking hours, I thought I would inquire as to whether I'm headed in the right direction by continuing to crank up subdivs or if there might be other approaches. Main problem I'm having in searching out the answer is that all of the tutorials and info I'm finding are in older versions of vray and the settings have changed so they aren't relative.

Also wondering what I might try to eliminate the artifacts on the ceiling by the pendant lights.

Thank You

[jasonstewart]

Can you post screenshots of all your vray/light settings. Without that its hard to see if something is off or if the scene just requires more subdivisions. The area on the left is definitely GI related. Is the only opening into the scene the window on the right of the frame? Trying to pack all the light through a small opening is tough and will require higher subdivisions to get smooth lighting.

 

What resolution are you rendering at?

 

Not sure what is causing those dots (I assume that is what you are talking about) above the pendants. Do you have render elements enabled? That would be the best way to track down where they are coming from.

[philvanderloo]

Thanks for taking a look Jason. I also have a sliding glass door to the left of the camera. I have vray plane lights in the windows on the right, and the glass door. Both with the same settings. (see attachments).

I'm rendering at 3000 x 2000 saving as 300 dpi tiff.

I'm not familiar with how render elements works but I'll research it.

[jasonstewart]

It seems like there is a vray sun also? What about your vray settings (sorry how I worded that before may have been confusing but all the tabs in the render setup would be helpful)? What method are you using to setup your scenes Vlado's Universal method or something like the Joconnell/Grant Warwick method? Or to put it more simply, are you trying to let the image sampler clean noise or eliminate noise at the source (lights, reflection, etc).

 

To add render elements just go to the render setup window and there is a render elements tab all the way at the right. Just go ahead add:

 

Alpha

Global Illumination

Lighting

Light select (This one you can make more than 1 and select different lights in each or a group of lights. It is very handy to tell what light is causing noise. I would add your vray sun to 1, your vray plane fill lights (windows and doors) to another, and the interior down lights to another)

Raw Global Illumination

Raw Reflection

Raw Shadow

Reflection

Sample Rate (this is a blue-red "heat map" to show how hard the AA sampler is working in different areas. Blue means that it is using your min and red is using the max, in between is in between)

Shadows

Zdepth (can be used later in PS to do DOF effect, set the distance to the distance between your camera and the farthest point it can see in scene).

 

I highly suggest watching these videos if you are interested in learning to balance your settings in order to decrease noise to get cleaner images in less time. Of course if you prefer to take a "Universal settings" approach that is ok too. The benefit to the universal approach is that you can spend less time messing with settings and optimizing your scene and let it render for longer knowing that you should get a usable result afterward.

 

http://vimeo.com/85982809

 

https://www.youtube.com/watch?v=pak8wx7KNEA

 

Both of those are good videos that show a new strategy that is becoming popular but they also explain very simply how vray uses samples and when to raise and lower them. Your image looks relatively clean but I just figure it would be helpful to you in the future and to possibly reduce render times.

 

To troubleshoot the GI I would hide the glass in the windows/doors and use an plain gray vraymaterial to ovverride all the materials in the scene. That will render much faster and you can slowly raise the subdivisions in your GI (IR+LC I assume) to remove the noise. Once that is done remove the override and it will render clean with your materials also. To figure out where those dots are coming from I would look through the render elements. It may be helpful to use some light select elements to see what light is causing it, it is possible that it is bouncing up off the pendant lights but its really hard to say. It could also be a strange artifact if there is a light that is intersecting geometry (they dont like that). Once you figure out where it is coming from it would be easy to remove it. You could of course remove it in PS fairly easily in post but it is always nice to have a clean raw beauty render.

[Zdravko Barisic]

Subs like 28 is too much, for Vray light, but that not point, just saying.

Post, please, render settings.

This kind of scene, should not be a problem for GI.

...

Also, you can upload clean scene, just lights and walls, no textures, somewhere on free server.

It should be like 5MB, no more. If someone has free time to check it.

Edited June 29, 2014 by okmijun

[RyderSK]

I would not suggest switching Workflow to above mentioned, i.e. Universal vs Grant/Akin. Those are great to use, if you're already perfectly comfortable and not beginner.

In Vray 3, it's best suggested to stay within "universal" means, because the parameter "Minimal Shading Rate" makes the same thing, just much faster, and easier.

The only pass which would show problem is "Global Illumination" but we can already see the problem from beauty render, the large walls have splotches due to inssuficiently allocated Irradiance map.

Rising the IR subdivs will not help the problem because even too many samples spread over flat surface will create artifacts. It's just shitty algorithm for complicated situations, that's all. But the subdivs are also governed by DMC sampler so make sure to user lower adaptivity, like 0.8, good noise threshold (0.002 for finals) and optimize your lighting. You can lower your subdivs, a to avoid artifacts in corners and get the detail back, you should instead use LightCache Retrace Threshold (will put more samples into corners) and Detail Enhancement in IR (which will use local brute force bounce inside corners and small proximity aread ).

You should be able to solve this sort of simple scene with IR, but if it cause much trouble, you can always switch to BruteForce in primary engine.

Edited June 29, 2014 by RyderSK

[philvanderloo]

Most of my settings in the final image posted were based on this tutorial

http://www.workshop.mintviz.com/tutorials/light-and-render-an-interior-day-and-night-scene-using-3ds-max-and-v-ray/

 

Some minor adjustments have been made since. The attachment shows where I am now. This is all great info. Thank You

Jason- I was capturing VrayextraTex and VrayWirecolor in emements to use in post but haven't gotten there yet.

[RyderSK]

Ok there are too many problems with the settings. What I really suggest, is not to use EXPERT/ADVANCED tabs at all and use Vray's help wizard to set everything for you. Use interior preset.

 

But anyway, the wrong stuff:

 

In GLOBAL DMC, you have GlobalSubdivMultiplier set to 0.1. It should be at 1. [Alternatively, it can be set to '0' to reset every scene subdiv if you use Universal approach,i.e. AA Min/Max 1/99 ]

 

You have Divide shading Subdiv checked ON,it's a feature that was created just to appease few users looking for linear way of adjusting Primary/Secondary samples without Vray compensating (dividing secondary samples by AA Max), it currently doesn't appear to work as expected maybe, and it definitely isn't feature to use unless you absolutely know what it does and why you want it.

 

Reflective GI caustics ON= in theory, this is the holy grail of realism, beautiful patterns of sun reflected on walls and ceiling from hitting reflective floor. In practice, it's close to un-renderable, in 99perc. of times, unless you perfectly know how to set-it up and have appropriate rendering capacity (10times bigger as without it) keep it OFF.

 

Huge ambient occlussion. There is almost no reason why to use AO directly as beauty pass overlay. It's ugly, but more so if you use huge radius like 10" and crazy amount of subdivs for rather crude effect.

 

Since you're already lighting your scene with VraySky, it makes little sense to keep AreaLights as additional light instead of keeping them as portal lights. I know the tutorial you followed has it set this way but it's different scenario and even then I would argue this is sub-optimal way how to things.

 

If you aren't exactly skilled compositor and don't know how to properly tonemap image in post-production, keep you Reinhard multiplier low, like 0.1. It will make everything easier for you, your scene will be brighter without overburns.

 

You have override depth set to 2. This is way too low number to use universally for whole scene. If you don't know when and why to set this lower for particular glossy materials, keep the number at 4. It's still low, but usable.

Edited June 29, 2014 by RyderSK

[philvanderloo]

Jason, Juraj and all. Hope you realize how much I appreciate you taking the time to help. Thank You and now I'll get to work on this advice.

[RyderSK]

At the moment, lot of people are still fighting on how to find the best settings, sweat spot, or ultimate holy gray within Vray. To be honest, even Vlado, main creator, is not really impressed with this endeavor, which is why they tried to simplify things in Vray3 as much as possible.

 

The setup wizard with preset sliders, and "Universal Settings" coupled now with feature "Minimal shading rate" (higher number means more secondary rays are cast, so more accurate glossy reflections, light shadows, depth of field effect,etc...). That's 3 buttons to touch to get where you want, without any hassle at all.

 

Anything else, is just looking for lot of uneccessary headache and trouble. Even after 3 years of using Vray day by day for 10 hours a day, I still battle ocassionally with balancing stuff. I can't imagine this to be worth for beginners. Just use the best of Vray3 for effortless work and then you can concentrate on the actual, creative part.

[jasonstewart]

I agree with Juraj to a point. The Universal Method is easy because you don't have to spend a whole lot of time chasing down one material or light that is causing you problems. I still think those videos are worth watching because it was an easy way for me to understand more about the inner workings of Vray. The problem with trying to fully tune a scene to render with as little AA as possible is that you may spend more time tweaking than you would have "wasted" as render time with universal settings. Your time is worth much more than your computers time so you have to realize that rendering overnight isn't a huge deal if when you wake up in the morning you have a usable image.

 

A lot of tutorials are really more harm than good. They usually don't explain WHY they are setting these settings the way they are. Without knowing why there is no way to tune. Every scene is different and I do think simplifying is best and slowly you will understand more and be able to fine tune different settings to get the results you want.

 

I know Vlado is unimpressed with the low AA method but you have to agree that it does work, its just trying to balance the time tuning vs. the time rendering. That is the key.

[RyderSK]

Well, I use the same method, even though I personally think that Connel's video is kind of fail...end he ultimately only ends up with ridicously high render time and odd choice of overall setup in first place ("complicated scenario" my ass...there's window taking 60perc. of image).

It also made a lot of sense in 2.4, because there was no way to balance primary vs secondary rays directly. But with minimal shading rate, that's exactly what's possible in 3.0.

 

But then there is real-life. I see so many rather let's say advanced users on Chaos, who just, completely fail to put the workflow correctly to practice, and then come crying back to Vlado for solution. And if that's the struggle pro-user have, what good does such advanced optimization brings to absolute beginner ? What does he gain outside of utter confusion ?

 

I just don't like giving advice without looking at concrete situation. Many people on this forum just go around with the "you should do it like we do" mantra, and force their latest discovery or some common knowledge. It's probably well-meant but it's misguided often.

 

Also, there's big hyperbolization being hinted towards that we're comparing "fast" optimized vs "overnight" universal. In conservative scenario, you can gain usually 30perc. of speed-up. It's not 1 hours vs 20 hours.

Edited June 30, 2014 by RyderSK