Black Dots in Interior Render

[iDon23]

Hi Fellows.
I am working on an interior scene and get wild black spots spread across the entire image, but also gathered around specific spots.

Using Keyshot 8 Pro
Lighting = Interior Mode
Shadow Quality = 3
Caustics = Off
Rendering to Max Samples = 450

I have a spot light over the fire place and a total of three more IES lights in the scene.
I tried removing the glass at the bottom right to see if that might be the cause of the issue, and indeed, the heavy black spot gatherings gone for the region at least. There are some fabric and translucent fabrics materials applied. I would also be happy to hear about some tips on how to reduce the render time as it took 24h for a 3840 x 2817 image with 300dpi.

[KristofDeHulsters]

If you share the package, I can have a look if it still brings it up in K10. I've had some materials in earlier version of Keyshot that completely crapped out but were fixed in the new updates. I would have said it's caustics but it more looks like a bug than anything else. In regards to your rendering time, I 100% prefer rendering on GPU which started coming along in K9. It makes rendering interiors much faster. You could possibly also render some parts of your images that don't need high samples separate using the region render tool and then compile them in Photoshop. It's a work around but it has saved me quite a bit of time before.

[Eric Summers]

I would have said it's caustics but it more looks like a bug than anything else.

I've actually had some really crazy caustic issues and black dots like this have happened to me before. I've even had some blue and magenta blobs in the past.
This could also be a physical light issue; I believe I have seen similar posts on the forum in the past like this. Try turning off the IES lights and spotlight one at a time to see if one of them is the problem.

[iDon23]

Thanks for the hint. I relocated the glass and the dots were gone. Also, Kristof checked, that indeed for KS9 and KS10 the issue does not occur in the same scene.