Problem scene with big delay once render completes

[tricky]

We are resurrecting an old project to do some further work. Its a complex model of quite a detailed classical building. Whilst the test render completes quite quickly (a minute or so at 640x480), there is a huge delay for many many minutes where the CPU locks at 13% (one CPU core I guess) and the ram usage also remains fixed. Typically, we have to crash out of the scene.

The scene uses around 4GB to open, and when rendering it peaks at around 20GB.

No displacement.
VERY simple light setup.
No GI at the moment.
We have run a cleaner script and there are no note tracks.

What could cause these delays?

EDIT: With the light switched off (a simple HDRI) the scene renders (obviously dark) but recovers quite quickly.
With the HDR switched on (all default settings) the scene doesn't tend to recover.

[svetlozar.draganov]

It sounds like a bug.

What happens if you remove half of the geometry in the scene?
And what happens if you remove everything?

Any plugins used in the scene?

Can you send us a screenshot from the final render?

[tricky]

Its two XREF scenes into a master file. The master file has only the camera and light. I have tried deleting the HDR light and using a vray sun/sky. Without GI, the scene renders quickly and recovers quite quickly. With GI on (LC/IRmap at low settings) scene renders quickly but doesn't recover. I will try again and also try deleting chunks of the geometry.

[svetlozar.draganov]

Run two separate renders with IM only and LC only.
You may also run a test with BF as well.
Try to reset V-Ray settings also by changing the Renderer to Scanline and then back to V-Ray.

[tricky]

Run two separate renders with IM only and LC only.
You may also run a test with BF as well.
Try to reset V-Ray settings also by changing the Renderer to Scanline and then back to V-Ray.

This is a fresh scene so render settings are at their default. The GI solution (when GI is enabled) calculates quite quickly. It is at the render end that the problem occurs.

[svetlozar.draganov]

Have you tried that scene on another machine?
Are there any missing assets attached via network paths?
Where is output image saved? Are there any active render elements?

[tricky]

No render elements.

We have tried on 2x workstations: mine which is spec'd in my signiture and a colleagues whose spec is an i7 with 16GB Ram and a Geforce card.

No missing assets.

No save image option is enabled yet.

[Morbid Angel]

You tried collapsing modifier stacks and things like that?

[vlado]

I guess it would be best to get us a scene for this.

Best regards,
Vlado

[tricky]

You tried collapsing modifier stacks and things like that?

We have made some attempts to do this but it is such a huge file (400-odd MB) that was modelled by somebody else that we have had limited success. Its a mix of groups and objects with some instanced modifiers and suchlike.

I set one computer trying to collapse the whole thing into a mesh as I think Max handles fewer objects better. The computer went on for about 1 hour and RAM rose to 10+GB but my colleague needed to use his machine again so we had to cancel - unfortunately we had no way of telling how far it had got.

Its very frustrating.

I think we are making some progress at the moment. There were some keyframes on some of the geometry (no idea why!) which we have deleted. Also, the camera we had inherited had motion blur on it. The scene was also coming from a Max2011 release with much older releases of Vray etc.

Fingers crossed.............

[stevesideas]

Can you convert all xrefs etc to vraymeshes ? That's what I normally do if these kind of problems occur. Much more efficient way of dealing with scenes.

[tricky]

I could try that. We rarely use vrayproxies these days. Is it possible to convert an entire scene into a proxy at once, even if some of the objects in that scene are instances?

[stevesideas]

I think that is possible. You just need to make sure that the option to save individual proxies is checked. Instances will be fine. Just make sure any xrefs are merged first.

[tricky]

Well, that project came and went, but I must say that a delay on render end is getting quite common for us. I am working on a simple scene with a HDR and simple GI setup. The GI and render (720p) calculates very quickly (40 seconds) but on render end, the max session takes several seconds (17 seconds) before I can continue working. With quick renders (particularly small test region renders) this is very annoying.

My display is set to Nitrous. I have a Quadro4000 card.

Any tips to speed this up?

(actually, looking at my initial thread, this is a different issue - I will start a new thread)

[Morbid Angel]

We had a similar issue recently. It turned out to be paths to the old network location in the render elements (which were created by maxstart.max file). Clearing thous fixed that issue.