Grainy Shadows

[wr_uk]

I'm new to Vray making the jump from mental ray recently.

How do I increase the quality and get rid of the overall graininess especially in the shadows?

[yolov]

Hi wr_uk ,

What are your render settings and what's the vray version you're using? Ideally, you should just increase the image sampler settings and vray should take care of the rest. I'd go with disabling DMC Sampler > use local subdivs, and then just increasing the image sampler max subdivs, while keeping the min shading rate somewhere between 6 ans 12. It might depend on other more specific settings, which is hard to advise towards or aginst without a scene and more details.

[wr_uk]

Using maya 2018
Vray 3.60.04

here's the Vray settings I used.

I didnt have DMC Sampler use local sub divs enabled.

Project file attached

[wr_uk]

OK so I think I figured it out. I swapped sampler type to bucket from progressive set shading rate to 6. render look good now but they are taking ages. What values should I be looking at to bring the render time down?

[yolov]

Generally, settings are scene-dependent. You can try different settings until you see what gives you the best noise/speed ratio. You start by lowering the max subdivs of the image sampler.
You can also go with more noisy render settings (i.e. lower image sampler settings) and use the vrayDenoiser to remove the noise, but keep the render times fast. https://docs.chaosgroup.com/display/...rayRE_Denoiser

[Morbid Angel]

so a couple of things:
you have the lamps in the ceiling set to direct illumination + multipler of 3. What that does is traces direct light rays from the laps but its not the same as having a light there. However you also have a light on top of it as well? which makes the sampling especially long and defeats the purpose of direct illumination anyway. So, put the lamp geometry into vray object properties and make it generate gi off and turn off direct illumination and just have the vray lights there.
The way you modeled the walls is incorrect. You have to make them as if in real life - meaning the have to have proper thickness. Having gaps like that will make light leaks and bad gi and heavier sampling. Same goes for window blid door frame.
what I suggest you do is replace the window blind plane you put in to generate exterior lighting with vray area light (its always more efficient to sample area lights then direct gi objects)
lastly, rendering with bruteforce inside interior is not going to be fast. In mental ray there was no way to really render with true brute force (not that I remember) so using biased methods like irradiance map will greatly speed up the interior rendering. With that said here are some quick tips on how to work with the noise:
Add a sample rate element. Set your dmc sampler (bucket) to 1/24 and noise thresh to 0.05. When you render you will see the sample rate element mostly blue, which means the dmc sampler is not reaching its max samples and therefore there is noise. Slowly lowering the noise threshold to a much lower value will engage the dmc sampler max subdivs a lot more, making the image cleaner. You want to avoid the case where your dmc sampler is producing all red, which means everything is being sampled at the max subdiv.
You also want to check use local subdivs and raise the shader subdivs a bit, or subdivs multipler as it helps to cleanup the noise. Here is the image which I got fairly clean in about 3 minutes of render time.

[wr_uk]

Thanks Morbid Angel thats a huge help for me!

[Morbid Angel]

Thanks Morbid Angel thats a huge help for me!

Sure thing! there is also a render element called denoiser. I highly recommend you add that and what it will do is cleanup the noise in post effect. Its perfect for interiors like this where you have a lot of monochrome space and it does it at almost no time cost.