Noise issue with multiple layers of transparent materials

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Benjamin76
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I am having difficulty dealing with the issue of getting an extra amount of noise when the rendered view features multiple layers of glass. I tested with different glass materials, from 100% thin film to 100% gloss and to a mixture of both. Transparent gloss materials give slightly less noise but I would lose the effect of double reflection for interior views.

Both samples were rendered with Presto(MC) @ TD=15, SS=High, Termination=512. You can see two layers of glass give much more noise to the scene. I've applied all common measures to reduce noise including tweaking wall materials and optimizing light design, etc.
Noise Issue_Through Glass.jpg
rac-basic-sample_ET08_104m.jpg
Does anyone have any idea about how to solve the issue or just lessen the symptom? Thanks
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nigec
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there's a thread in the su section last week, two in fact about this kind of issue.. not that there was a definite answer.. I'd imagine 512 sp isn't enough
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george
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Have you tried turning off the Shadow Caster option for the window panels while keeping the Glossy material?
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Hieru
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nigec wrote:I'd imagine 512 sp isn't enough
That's my thinking.

Despite the difficult conditions the noise isn't too bad in these images. I would expect to use at least 2000 s/px for most interiors and 4000+ s/px for really difficult/complex scenes.

If you can't wait that long, render until most of the scene is clean and then region render the problem areas.
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george wrote:Have you tried turning off the Shadow Caster option for the window panels while keeping the Glossy material?
I tried. Somehow that even gives more noise.
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Benjamin76
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Hieru wrote:
nigec wrote:I'd imagine 512 sp isn't enough
That's my thinking.

Despite the difficult conditions the noise isn't too bad in these images. I would expect to use at least 2000 s/px for most interiors and 4000+ s/px for really difficult/complex scenes.

If you can't wait that long, render until most of the scene is clean and then region render the problem areas.
Other interior scenes are actually quite nice at 512. It is just this interior scene that allows you to see through two layers of window panes that have weird extra noise.
rac-basic-sample_IT03_107m.jpg
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Hieru
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That's because the caustics generated by the glass take a long time to resolve.
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george
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What happens if you render in clay mode? Do you still get noise?
As for the Glossy material, if you have shadow caster on, then caustics will be generated. It is a very difficult situation for Presto to solve.
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george
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I love your lighting by the way! :)
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Which windows have the double sheets of glass cause i dont see multple reflections?

Perhaps try to give the second sheet less IOR value? but this will mean less reflections strength
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