Grainy Render - how to improve?

Started by CADCAM10, December 13, 2021, 08:17:03 AM

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Good morning. We're still struggling with interior renderings, but it's a learning process. I've attached a render we did in keyshot 10 at 600 samples, 300DPI, still incredibly grainy. I've tried the noise feature but it makes the image look very airbrushed and blurs things that should be sharp.

Lighting setup: I have 2 very bright area light panes hidden from view on either side of the cabin through the glass with a HRDI scene of the sky. The interior lights are IES profiles with good lumen output. Alternatively I also added a lighting pane just below the ceiling system but it casts shadows that I didn't like so you see a rim line around the room.

Do you have any input on how I could improve this and reduce the grain, do I just need to blow out the lighting more than I have? Or is the light coming through the glass problematic? Thanks for your help.

Anindo Ghosh

Reducing the Denoise Blend ratio might help arrive at a balance between noise reduction and loss of detail. Values between 0.5 and 0.8 work best for me, depending on lighting and image specifics.

Also, for an image like yours, I would use 1000 samples or more.


Thanks for the tips. I've never used the denoise feature in previous KS versions with similar interiors. I did usually put a fairly bright hidden ceiling plane area light to improve but never had issue with such grainy renders. Is there something I can do otherwise to improve this, or is it just a lack of good light inside? I see others on the forum get crystal clear interior renders that have much more realistic lighting.


Well I think there are several parameters to take into account, on the one hand the GPU vs CPU rendering mode, very often on complex interior scenes the GPU rendering mode generates more noise  than  CPU mode, on the other hand the selected rendering mode also plays an important role,  product mode or interior mode where interior mode often generates less noise too (imo) / other aspect is the scale of the scene that can also play an important role, changing the scale of the scene can allow in some cases to better control the noise; finaly of course lights (intensity , position) is also a key factor, denoise setting IMO is the last thing to activate & tune if you still have residual noise , but there is no miracle recipe either you have to experiment overall to find the settings that subjectively you will find the best one.


See attached render at 1000 samples, 0.5 Denoise, still very grainy. I've also attached a screenshot of some of the settings. The results aren't very impressive for nearly double the render time, and as indicated above I do too feel denoise or any post process should be a last resort. I never had to do this in previous versions and I used similar lighting strategies, albeit I never used IES lights before and would just use a handful of light planes interior/exterior.


It's not uncommon for interior scenes to have 2000-3000 or more samples.