Proxies disappearing on old CPUs after the first frame

[DanGrover]

Hi Guys,

Quite a weird one here, but I'll keep it short. Max 2021, VRay 5.2. If the following conditions are all met, a bit of geo disappears from the render without any error.

1) The CPU in the machine rendering the frame is an old one - based on my limited information, one's that the Vrayinfo.cpu metadata embedded into the .EXRs refers to as `INTEL/Model:12,Family:6,Stepping:2,Cache:0` cause problems (it's an old Xeon X5660 from ~2010)
2) It's *not* the first frame that machine has rendered since loading Max.
3) The Proxy in question has a modifier on top of it.

(Yes, yes, yes, I know, we shouldn't be putting modifiers on top of Proxies, but sometimes it's preferable to suck off the loss in efficiency for the sake of a quick tweak.)

One interesting thing to note is that the 'primitives' count in the same EXR metadata window shows the exact same number whether it's a successfully rendered frame (on an `INTEL/Model:15` machine) or one with the missing geo, which leads me to think that it's either present but in the wrong place or otherwise transparent for whatever reason.

There are lots and lots of workarounds - re-export the proxies with the modifier applied, export as .vrscene and render it standalone so the mesh gets crunched down, force the machines rendering to restart Max on each frame etc - but I'm curious as to why this might be happening. Given it appears to relate both toe geometry and to CPU type, my Spidey senses are telling me that it's perhaps an Embree thing, where it's able to load it initially but then refreshing the scene data for a new frame causes it to go AWOL for some reason? Just a guess.

Any ideas?

Thanks!
Dan

[^Lele^]

(Yes, yes, yes, I know, we shouldn't be putting modifiers on top of Proxies, but sometimes it's preferable to suck off the loss in efficiency for the sake of a quick tweak

That's not been a problem for a long time, per se'.

It would be best to send us a scene which you are sure suffers from that behaviour with that CPU, so we can investigate it.
It could well be acceleration structures, but it could also be due to Max (and some bug in the specific modifier/scene setup).

[DanGrover]

That's not been a problem for a long time, per se'.

Ah, really? It was the first thing I checked, and sure enough the Vray 5 docs do still state that "When a modifier is added, the proxy loses its memory-saving properties and is regarded as just a regular mesh in the scene."

It would be best to send us a scene which you are sure suffers from that behaviour with that CPU, so we can investigate it.
It could well be acceleration structures, but it could also be due to Max (and some bug in the specific modifier/scene setup).

Sure thing, I'll try and get as small-a scene as possible and post back when I have it.

[^Lele^]

Ah, really? It was the first thing I checked, and sure enough the Vray 5 docs do still state that "When a modifier is added, the proxy loses its memory-saving properties and is regarded as just a regular mesh in the scene."

I wasn't very clear, apologies.
I was referring to the fact that adding a modifier to a proxy would return a mesh composed of the vertices/triangles visible at the time the modifier was added, so the stack, and renderer, would use the triangle skipping Preview, f.e.
Now, the switch to full mesh, and hence ofc loss of dynamic loading/unloading, is done automatically for the renderer.

Sure thing, I'll try and get as small-a scene as possible and post back when I have it.

Many thanks!