White dots on glossy glass + HDR

[vicnaum]

There are bright dots on glass with 0.6 reflection glossy. The dots only appear if I enable refraction.

The scene is a simple sphere on black plane + HDR.



20 minutes, 200+ passes, the dots don't disappear.

Here you can download the scene (or create one yourself):
https://www.dropbox.com/s/sblsxb55azz219z/refraction_dots.max?dl=0

Here is a HDRi:
https://www.dropbox.com/s/113sm77dh9asya2/04-28_Night_C1.hdr?dl=0

The build is latest 21 Dec, the settings are all Default.

Am I doing something wrong?

[borisquezadaa]

I can reproduce your issue. Here is clean at 300 passes no alteration done to your file. And i have no brigth dots.

[vicnaum]

Yeah, I believe the noise will disappear sooner or later. But that's surprising that the simple 2-object scene is rendering so long.

But... Here is >1000 passes, and still dots:

[borisquezadaa]

I would like to notice that in Corona A7.2 (no daily) the noise clean way faster and dissapears completely after 300 passes more or less, so there is something fishy going on here.

[vicnaum]

Here I did a comparison of A7.2 and the latest Daily 19.01.2014 (look at the gif in attachment)

The A7.2 doesn't have GGX, thus there is a visual difference with the daily. But anyways - daily reflections look far too more noisy, and take longer time for the same amount of passes.


Here is also the PSD for those who want to examine it closely: https://www.dropbox.com/s/748tpwj3limydh1/a7.2_19.01_comparison.psd

[Ondra]

it looks fine, more noise is just consequence of the GGX lobe being wider. It is the cost for more realistic materials.

[vicnaum]

Yes, the lobes are different. But I'm more concerned about next things:
1) Individual dots still present on 500 passes, and a couple of ones on 1000 passes
2) 30% slower time for same passes count (but don't know about this - maybe current passes are "cleaner"?)
3) Do we really need 1000 passes to get a clean glossy without dots?
4) Even on 1000 passes it's still noisy: http://www.naumik.com/temp/scr5/20150120-3in-34kb.jpg

UPD: to make it fair - I did the same test with non-GGX legacy mode on latest 19.01 build - yes, it looks the same now, just 20% longer. And glossy value 0.6 -> became 0.73 to look similar:
https://www.dropbox.com/s/egdeb3a6nvkk962/daily_19.01_nonggx.psd?dl=0