Interior/HDRI Visible Behind Glass - Major Noise Issue

[dj_buckley]

So I'm rendering an interior - I have it setup with 2 dome lights both have HDRI's loaded via a VRayHDRI Map - 1st dome is invisible, and just contributing to the diffuse and shadows, the 2nd dome is visible and affecting specular and reflections only. The 2nd dome contains a different HDRI with a significantly lower Overall Multipler in the VRayHDRI Map. I do this so I can control reflections/specular independently of the lighting.

However, if I leave the 2nd dome visible so that I can see it in the render, the glass panes become incredibly noisy in the rawreflection pass, unusable in fact. Everything else in the raw reflection is noise free. If I make the dome invisible - the raw reflection pass is super clean. This is happening on any transparent objects that the HDRI is visible behind.

Just wondering what the issue is here as I'd like to be able to render with the 2nd Dome/HDRI visible in the render behind the glass but currently I can't due to the effect it has on the raw reflection pass.

Anyone any ideas?

[tashko.zashev]

Hi,

From what I can see in the screenshot attached, most probably the issue here is that the image sampler works with respect to the beauty pass and thus can decide to put less or more samples in a specific render area. Usually the image sampler casts more rays on darker areas which automatically makes the Raw reflection pass better.
Are you able to get clean raw reflection by adding more sampling ? Lower Noise threshold, Min/Max subdivs 4/24 for an example.
Furthermore you can try to add in the render elements list a V-Ray SampleRate element and see how many samples are used in both cases.

You can also send your scene file for inspection to support@chaosgroup.com so we can take a look at the render settings and render results.

[dj_buckley]

Thanks for the response. What I don't understand is why it's only happening on the transparent objects? It's a reflection issue rather than a refraction issue, and is only happening to the objects with 100% reflection. I'll send the scene to the email address you provided. My settings are pretty high already, as I say the rest of the scene is super clean, you just need to look at the window mullion to see that. All this is telling me at the minute is I can't render an interior scene with an HDRI visible out of the window.

[tashko.zashev]

Yes, please send us the scene file so we can take a look and provide more precise solution for this problem.