Interior rendering problems

[ingoerik]

Hi everyone,

i have a problem getting a clean interior rendering with VRay. Attached is a Diffuse Direct Light channel that shows the problem, lots of grain in the shadows; strange enough nothing on the floor. Its obviously not that much in the rendering, but since i add contrast to the rendering its still visible. The grain comes from the hdri that is attached to a dome light, rendering is IC/LC with adaptive sampling, threshold is already at 0,002. Rendertime is 9 hours on my computer, Modos renderer delivers a clean picture in 3 hours, just as a comparison. I also tested different scenes and different hdris, but its all the same.

I can make the subdivision setting for the dome light higher to get a clean rendering, but than the rendertime gets insane; the same happens when i use the hdri in a modo environment and use the EIS settings. Rendering brute force makes things a bit better, but rendertime gets slower too.

Sooo, any tips for getting a clean rendering are welcome.

[ingoerik]

Here is the rendering :

[ingoerik]

to avoid misunderstandings, its not the overall noise but its the biten edges i like to smooth out. Attached is again a diffuse direct light channel, this time its at print resolution.

[Muhammed_Hamed]

rendering is IC/LC with adaptive sampling

Is this a typo or are you actually using LC as primary GI solution??

I can make the subdivision setting for the dome light higher to get a clean rendering

Does this mean you have local subdivs on in your render settings?

If the answer is yes, This is not really how you are supposed to use Vray. Reset you settings to defaults first, then try these settings(very important to reset)
Sampler type, adaptive(bucket)
min subdivs=1
max subdivs=32
min shading rate=16
noise threshold=.008
Then change LC samples to 2000 (default settings should be BF+LC don't use Irradiance map)
And dynamic memory limit to 0 which should be the default setting I think.
Now add sample rate render element and hit render. Let me know what kind of render time you are getting and screenshot your sample rate pass here

Never use LC as primary GI.. It is not meant to be used as a primary GI solution.
Never check use local samples in your render settings. Vray is smart enough to determine the best amount of samples for your lights/materials..etc and sampling in Vray has been all about ease of use.
Another note is that you need to use portal lights to guide GI through your windows. This will speed up things at least 4 times, and you will get more illumination in your interior.

[ingoerik]

Thanks for your tips.

Well, i wrote that i use IC for Primary and LC for secondary rays, so nothing special. Brute force smoothes this edges a bit but i get a much higher rendertime (to clean the noise) and have to be more careful with bump mapping since it gets more visible with BF.

Yes, i used local subdivs since Vray is not smart enough to deliver a good result ... or better said the overall result is good but not these special parts on the walls. And i would like to know why its only so noisy on the walls, i tried the floor texture on the walls but it gives me the same amount of noise. Since this is only because of the hdris i tried to work locally only on the hdris instead of finetuning other parameters that affect everything else in the scene too.

I will try your settings but so far i haven't found "dynamic memory limit" nor a "sample rate render element", do you use a newer version ?

[Muhammed_Hamed]

Check out my screenshot for sample rate and dynamic memory limit.

Yes, i used local subdivs since Vray is not smart enough to deliver a good result

This is not true... Pls use my settings, then we can compare render time and quality of shadows..etc
I've probably done more sampling tests in Vray more than 99% of users.. You really shouldn't use local subdivs
Using my settings with BF will be faster than what you are currently using. Upload your results here so we can compare

Brute force smoothes this edges a bit but i get a much higher rendertime

No, it doesn't

And by the way, use my settings for all your scenes.. they will work perfectly fine and you will only need to use noise threshold to control render time/quality .. aka if you have noise with .008, you can try .005 and you don't have to change anything else.

[ingoerik]

Thanks for your help so far, i am still working on it. I rendered over the weekend a test with BruteForce and your settings, and Threshold at 0.002 which looks okay but took 17 hours to render.

Since the file is a bit older i go now through all the render and light settings and change them to default, next i use a default grey material for all but the glass and render it. That way i am sure that any old weird textures are not the problem, i'll post it tomorrow.

[boyan]

Hey, all,

Thanks for the posts. ingoerik I think the portals might be a reason for this noise level, try to replace them with Area Lights. My best advice is to render the final image as Muhammed suggested to you and also to enable the V-Ray denoiser, which will clean the noise at the Final Image (RGB). As for the other render elements, the best way is to clean them in PS with post-production denoiser. In the future when V-Ray Next for Modo come this will be avoided because denoiser will work for the rest render elements, too. You might try also to use and really lower threshold 0.001 with Progressive but the render time will increase.

[ingoerik]

Thanks Boyan. I have no Portals or Area Lights in the windows, just the HDRI map on a DomeLight (so no Modo Environment too). I guess progressive wont work on a render farm, i send the finals usually to GarageFarmNet since my computer is to slow.

I think some of the noise comes from the green stuff outside, the replicated grass and hedges and the trees.

[Muhammed_Hamed]

Another note is that you need to use portal lights to guide GI through your windows. This will speed up things at least 4 times, and you will get more illumination in your interior.

This is from my first reply(pls follow my settings to the letter, this will help you solve your issue faster). You really cannot use an HDRI for interior lighting without portals.
The sample rate render element will show this as most of your GI will be all red.. I need to see your sample rate render element.
Using area lights will help as well, but judging from the screenshots above, you have big windows and portals should do a good job
If you cannot get a clean render with .008 noise threshold and the settings I posted above, you probably have something wrong in your setup
Portals will give you more illumination in your interior and it will be 4 times faster in rendering.

[ingoerik]

Okay, now the pics direct out of VRay with Muhammeds settings, one with portals one without. The difference in rendertime and quality is not that much.

[Muhammed_Hamed]

Thanks for sharing!
sample rate RE really shows what is going on.
You can see in areas of shadows, Vray is having a lot of trouble without portals(green noise in sample rate pass) and the render with portals is much cleaner(even if render times are not that different) and your interior is way brighter.. your shadows are softer and much more realistic as if you were using BF+BF with high GI bounces.
This will make a huge difference for calculating samples of the materials as well.
I would recommend you exculde all windows glass from the GI calculations of the dome light and portal lights(If you cannot exculde the environment, make a dome light and apply your HDRI to it, it will give you the exact same result)
What noise threshold are you using?
Are you using Bucket samler(progressive will be slower for this kind of scene)
Now you can render your final images and let us know what kind of render times you get
Also compare closely your beauty base from your LC+LC rendering to my settings. I do know that the difference is massive and it should be(LC is not accurate at all as a primary GI solution, BF is miles ahead in quality). let us know

[Muhammed_Hamed]

and quality is not that much

use the AB comparison feature from the history panel in the VFB and zoom in with your scroll wheel in areas of contrast. Do you see any difference in noise pattern? what about shadows?
The difference is massive. The high frequency noise will be huge issue for Vray for final rendering. Check out the GI Render element and maybe the diffuse direct light RE that you used in the first post.

[ingoerik]

Hi Muhammed, thanks again for your comments. Window glass is already excluded from GI and lighting is by a hdri on a domelight, no Modo environment. Noise threshold of the adaptive sampler is on 0.007. I guess the only way to get it cleaner is lowering the noise threshold, i dont know if adding an additional light inside gives a better GI solution since the noise problem is only on the ceiling and the two walls, the rest of the picture has a very good GI quality.

Now i have to work on the textures, because when i switch them on i get a lot of additional grain.

[boyan]

Hey, ingoerik

Replace the portals with Area Lights, Enable Environment Map and add an HDRI texture map to it next disable Indirect Light option from the properties menu, change the Light intensity of Area Light and let's try how clean render will be.

Cheers,