Strange behavior when rendering interactively

[CASA_MT]

hey guys,

I am writing regarding a strange issue we came across during the last two productions, both times we encountered the same behaviour.

The situation:
In our studio, we do ArchViz (using 3ds max) and use a lot of High Poly props (Some scenes have around 15,000,000 polys in just one room).
So far, Corona could handle even this amount of polies even in interactive mode (and sometimes even with Hair and Fur enabled). Of course it took a while to get an image, but it was okay working this way and of course it is much better compared to Vray (we did not even bother using RT there, it was just too slow).

In the last production, I had to visualize a room with a lot of clothing. After merging a certain type of 3d-model from our stock (some T-shirts), I could not use Interactive mode anymore. Well, I could still press "Interactive" and Corona tried to start it, but no image came up. I looked at the task-manager and noticed a strange bahaviour (you can see a screenshot attached). Basically the processing power and the RAM go up and down, but the CPU never reaches a constant high, like when it is rendering. At the time I blamed the 16 GB of RAM and simplified the scene until I got it working again (that was not very fun, I had to check every prop, until I found out that the T-shirts were causing the trouble). The strange thing is, that the T-shirt material seemed to have caused this, although it was not very complex. I created a new one from scratch and this one worked again.

Anyways, yesterday we got an upgrade from 16GB RAM to 48 GB RAM and I was eager to see if I could get this scene working now. But still, it was the same issue, just without the Corona-warning, that I am running out of RAM. My collegue also encountered the same behaviour in another project which was completely unrelated to mine. If this problem was just on my machine, I would have blamed it on the file, but in this case, I am starting to get a little nervous. Is this something, anyone has come across so far?

We are using 3ds max 2017, newest SP and newest Corona Daily Build.
I also checked the file in 3ds max 2016, Corona 1.4, same problem...

[maru]

It looks a bit like IR is restarting infinitely. Does it eventually start or not?

What kind of model was the tshirt which caused the problems? Also wat kind of material was that?

Is there a chance you could send us a problematic scene like that, or a part of it which is causing the problem?

[CASA_MT]

Maybe eventually IR will start showing a picture, I waited around a minute or so and often decided to abort it, often times even crashing 3ds max.

The t-shirts were models which we bought some time ago from http://www.viz-people.com/
They seem to be simulated meshes, but they are heavily optimized before export, so that they do not contain any really heavy geometry.
My collegue did not use any models from this collection, when he encountered this problem, so this collection is not even something I could point my finger on. It is all very strange.

The material itself is really simple, just a Falloff in the diffuse-slot and a little bit of reflection (not even bump).

Maru, I sent you a PN with a download-link for the problematic scene. The shelf-system has been removed, as it was the product of our client, the problem is still persistent. I am really corsious, if you encounter the same issue.