Noisy interior

[Specto3d]

Hi guys!

I've been using Corona for a while now, and must say I've been pretty satisfied so far.
Until I worked on last project which took 5 hrs rendertime on my i7-3930k + 2×i7 4790k slaves with 1920/1200 resolution.
That was quite unpleasant surprise, since it needed to be finished quick, and noise free, but I got stuck with rendering.
Scene have hdr in environment, portals properly mounted on windows, I've checked albedo.
I've noticed direct lighting gave me noise in some shadow areas, but indirect pass was totally clear, so I decided to raise LSM to 32, and leave GI/AA to16.
That gave me equal amount of noise for direct and indirect passes on start of render, and shorter rendertime in general, but still too lonf.
Did I miss some setting? Could anybody help to get rendertime shorter or determine problem, so it could be avoided in future?

[hrvojezg00]

from my experience, most noise came from IES lighting, check if that is the problem. if it is, try changing shape from disk to sphere or rectangular, worked for me.

[maru]

Hi Specto, it would really help if you could post some renders, viewport screenshots, or at least describe the scene in detail - what kinds of lights are you using? What kinds of materials? Are there some "non-standard" objects or textures - for example coming from 3rd party plugins? Are you using standard camera or maybe Vray camera? How is HDRI loaded?

[Specto3d]

@hrvojezg00: I've used hdr in vrayHDRI map, with one coronaPlane light behind camera position, one coronaPlane light above sofa, and one sphere light in a bedroom lamp (IES is by default on, but there's no map-could that be a problem?).
Here's re-rendered scene with i7-3930k with critical beauty, direct and indirect pass crop. There's no reflection, or bump map or anything similar on white wall material, it's plane white diffuse material.
Most complex material could be basin material which is a blend material with coronaAO and falloff maps. Multi-texture map is used for wood floor, and that's only plugin used.
There's a corona light background cylinder to fake outdoors.
There is a coronaProxy carpet object which has 3M polygons originally.

It wouldn't be that much of a problem if I wouldn't use Photoshop plugins for contrast and a bit of sharpening, that's when noise pops out.

[romullus]

IES is by default on, but there's no map-could that be a problem?

No. That checkbox doesn't matter as long as you didn't assign ies file to light.

There's a corona light background cylinder to fake outdoors.

That could be a problem if you didn't take care to assign proper material to it. Take a look here how to do it properly: https://coronarenderer.freshdesk.com/support/solutions/articles/5000515605

[Specto3d]

Background cylinder without base and top has CoronaLight with emit light option turned off.
Here's same scene rendered without this background object, and without floor material, as I suspected it could be choking render, but rendertime is similar to previous.

What could be expected rendertime for 1920/1080 resolution render?
Maybe this is normal for interior renders?

[PROH]

Hi. Have you tried removing/disabling all AO maps? In my experience AO maps often results in a low pass number combined with very high ray numbers - just like your numbers.

Besides that, there isn't much light coming into your apartment. Maybe you should try to turn on the light in the kitchen?

[Specto3d]

TRied to turn kitchen light on, but client requested to remove it.
Will try AO though! Thanks

[Specto3d]

I finally got it. The problem was in scene geometry: it needed too many bounces because kitchen is rather far from window, which is only lighting source.
Solution is either in turning interior lights on to get more direct light samples, or introducing more samples from HDR from outside which results in longer rendertime.

thanks PROH!

[Ludvik Koutny]

Actually, these are the thing that could be going in your scene:

I would check brightness of colors on your materials. Especially kitchen furniture white seems to almost glow. Corona as well as other PBR path tracers does not deal well with super bright colors, so you should never go over RGB220 white. Even if you checked albedo, i would double check that kitchen furniture.

You have large deep window with small opening through which light enters. You should put portal in there. Just create a plane to cover window opening, and assign CoronaPortalMTL over there. Set LSM back to 2-4. 32 is extremely high and inefficient value.

The background cylinder should have CoronaMTL with 0 diffuse and image plugged into self illumination slot. This CoronaMTL is then fed into direct, reflection and refraction slot of CoronaRayswitchMTL, which is assigned to the cylinder. Global Illumination slot of the RayswitchMTL remains empty.

This should make your interior render fast.