Building acceleration structure - what does it depend on?

[pokoy]

Corona 1.4, max 2016

I have a slightly complicated CAD scene where the 'Building acceleration structure' takes anywhere between 3 to 50 seconds. After observing this random behavior I played around a bit and found that these things may make a difference in scene parsing time:

- changing point of view (orbiting around the model, the whole model is visible always but for some reason parsing time will change)
- changing a certain material's reflection glossiness value from 0.25 to 0.15 will increase scene prep time... I don't understand why but this is what happens here.

Is this supposed to happen? I imagine that reflection glossiness may result in a different ray distribution but haven't observed this before... Any pointers what else to check?

[Ondra]

changing point of view can make a difference if the geometry is view-dependent - body object in 3dsmax, or displacement. Reflection glossiness should have no effect at all, it is probably a random variation

[pokoy]

It's all mesh geometry, no dynamic tesselation, no displacement either... changing reflection glossiness adds 40 seconds, but changing it back doesn't change anything anymore. What's strange is that it didn't happen yesterday but was quite obvious today. Will give it another go with a fresh max session then.

[Ondra]

most obvious asnwer would be memory space fragmentation or exhaustion... how is your RAM? Can you screenshot the performance->memory tab of task manager during the long parsing?

[pokoy]

Plenty of RAM available. It happens now during IR with a very simple single object and it takes 40 seconds to update, it's totally random.

Nothing changed from yesterday, only a minor Win update with new defender definitions.

[pokoy]

I have disabled Windows defender but it didn't help...
RAM usage stays stable, no peaks. CPU usage is around 95-100% in IR mode but will go all the way up to 100% when the issue starts and it stops responding unless it's done with whatever it does.

How can this be so erratic? I was working with the whole model in IR mode yesterday, tweaking shaders and whatnot with no problems at all, and now it's crawling and taking long breaks every second change of a material or a map... Feels like I'm on a really unstable daily build, not sure what to do.

[pokoy]

Just tried the latest daily build and, unfortunately, I'm getting the same problem there, too.

I guess it must be something with my system (could a Windows update really screw this up?) or it's a problem with the scene... which was not present yesterday.

It's not only IR mode, Max freezes when I open the material editor for the first time, on scene prep, or when I cancel a render where it takes 2 minutes to response again, or when changing material properties.

[pokoy]

Sorry for the wall of text, here's an update.
I restarted the PC and Windows had some updates to install (I guess they were released today) and it seems to work fine now... Fingers crossed.