A lot of noise when rendering with light portals

[martynaaas]

I'm trying to render an interior scene and testing a few settings with Vray rectangle light set as light portal. I got those nice shadows where objects meet ground, however it got way too noisy now. Does this noise come from low subdivs of rectangle light? Or any other settings?

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[valerostudio]

I stopped using light portals. The render times were isane and I did not find that added to the quality of the image, just use regular rectangular lights if you must.

[martynaaas]

@valerostudio said:

I stopped using light portals. The render times were isane and I did not find that added to the quality of the image, just use regular rectangular lights if you must.

It did increase render time indeed, although I was able to produce those sharp shadows on the ground. I guess it really depends on the quality of renders you're looking for. For this project, we are working on a high-end interior so producing qualitative renders is a must.

Going back to topic, I was able to reduce noise levels dramatically by checking Sub-pixel mapping option under Colour mapping menu. It's still a little bit noisy but not as much. Changing subdiv count under Vray Rectangle light options did not do too much (went from 8 to 64 and could barely notice a difference in noise levels but shadows got a little bit smoother).

[valerostudio]

You cant depend on solely exterior light to render an interior. You need to add lights, the same way you would need to light a space in real life. Sometimes I add a couple of planes just inside the windows to fake in some more light, but you definitely need more lights in your scene or you are going to get splotchy renders.

[martynaaas]

@valerostudio said:

You cant depend on solely exterior light to render an interior. You need to add lights, the same way you would need to light a space in real life. Sometimes I add a couple of planes just inside the windows to fake in some more light, but you definitely need more lights in your scene or you are going to get splotchy renders.

I have to disagree with you here. I use HDRI + VraySky most of the time which gives me more than enough lighting for any interior scene (considering that an interior has a right amount of openings). I guess your statement is more valid when doing night/evening renders.