Fireflies issue with 3.20.01 nightly

[Julio_Cayetano]

Hi, my name is Julio and I´m currently using RT GPU (and Octane) for my production rendering.

For testing purposes, I´ve just re-rendered a project with the latest nightly for 3DsMax 2014 I´ve found, 3.20.01. It was originally rendered a couple of weeks ago, with 3.10.03 I think.
The overall noise is handled better I think, and the "Max. noise" param. seems to be working properly now. So I was able to render it faster, but I´ve found a new issue that wasn´t there before. Lot of fireflies that seems to be coming from the Dome Light. The scene is lit by that DomeLight (hdri) and a couple of flashes (simple area lights).

I´m attaching crops so you can compare before/after results with same (or very similar) settings. Is this a bug? Any suggestions about how to solve this?

I will try to test other scenes to check this issue.

Thank you very much in advance

Julio

[vlado]

Looks like a bug to me. I would very much like to take a look at that scene (you can strip it down, I just need to be able to reproduce the fireflies). You can send it to vlado@chaosgroup.com. Thanks!

Best regards,
Vlado

[Julio_Cayetano]

Simplified scene sent.

Thanks a lot for the fast support.

Julio

[3LP]

I had the same issue few days ago when I rendered the simple shader ball of GW.
If needed, I can try to dig it up to send it as well.

Cheers
Stan

[Julio_Cayetano]

Hi Stan,

I can reproduce it in Grant´s shader ball scene too, with various metals and glossy materials.

Looks like a bug indeed. I just hope it will be easy to fix....

Best

Julio

[vlado]

Yes, it's easy to fix... thanks a lot for the pointer!

Best regards,
Vlado

[Julio_Cayetano]

My pleasure, Vlado.

I´m glad to hear that It isn´t too complex to fix.

Best

Julio

[vlado]

No problem. I see that you are using the "Coherent tracing" checkbox. Have you found it useful? I did it as an experiment, and it does trace a bit faster but I wasn't sure if people will like it.

Best regards,
Vlado

[Julio_Cayetano]

Good question, let me give my point of view here:

I was testing it too, and I´m not really sure if It was better or not. For the first interiors I rendered with "Coherent tracing" ON I realised that I was gaining some speed in tracing (maybe around 10%) but I was getting a dirtier result for the same amount of rays. Maybe It´s just because I was stopping renders too soon. So I wasn´t really sure if I would keep using it.
In the last nightly, only a couple of tests done, I think I can´t see that "dirtyness"... does it make sense? maybe I should do more tests. In Octane (It has a "Coherent ratio"), I usually render with that option ON and I can´t see relevant drawbacks (only the speed boost).

Best

Julio

[vlado]

Ok, thanks. I'm not really sure if does the same thing as Octane though - I haven't really played with it. In any case, if you feel like experimenting, any feedback is welcome.

I found the problem, and the fix will go into the 3.20 builds next week.

Best regards,
Vlado

[3LP]

Great news

Stan