Prepass DR bucket "lag" problem

[king_max]

Hi. I'm having this strange issue in the latest build of vray. When rendering an image using DR, 90% of the prepass phase is done in let's say 10 minutes, then the last buckets from the render nodes take another 10 minutes to finish, and the very last bucket takes even 20 minutes to render?!?
It's insane because if I rendered the image through backburner (using DR again) it would render in 15 minutes.
Does it have anything to do with the LC retrace option? Or could it be influenced by the "low thread priority" option?

[vlado]

Is this for V-Ray 2.0 or 1.5? Also, are there other programs running on the machine which is rendering those buckets? Is there anything different in those buckets than the rest of the image (e.g. objects with more glossy reflections, stuff like that)?

Best regards,
Vlado

[king_max]

This is for V-Ray 2.0. The machines are running only vrayspawner as a service. It's difficult to say if those buckets hits any particular surfaces. My guess is that they "stuck" on some more machine intensive zones. (e.g. glossy object, plant leaves, small detail geometry). The general rule is that the last bucket/s takes ages to finish.
I can't recall if it happened on V-ray 1.5

As I wrote this post I've noticed that on low (preview) settings it doesn't occure.

[vlado]

If you reverse the regions sequence, do you still get the same buckets to stick?

With V-Ray 1.5 there was an issue where the last bucket would not finish at all.

Best regards,
Vlado

[king_max]

I'll give it a try right now.

[king_max]

I've attached a screenshot. Clearly those are "tricky" zones to render, but if you look at the image, the same machines have already rendered all the other buckets that are close to the ones missing and those had the same amount of glossyness and details. Now it hangs like this for 10-15 minutes slowly completing each missing bucket and the final will take "forever". Is there a workaround for this? Decreasing the bucket size perhaps?
I'm just doing a quality check of the frames in the animation, but can't afford to lose 1 hour each time. As an example, this scene prepass will be rendered through backburner and it will render in app 1 hour and it will take 20ish minutes per frame for the final renders on dual xeon 8-cores machines. (the same machines used in DR in the first place)

[vlado]

Hm, you can try disabling the 3ds Max bitmap pager and/or reducing the bucket size. Are there any V-Ray proxy objects, or displacement in the scene? But in any case, it would be good if you can send me the scene to vlado@chaosgroup.com for investigation.

Best regards,
Vlado

[king_max]

No proxies nor displacement. I'll send you the scene as soon as I get some free time. I need to finish this job asap. Deadline knocking on the door as usual.
By the way. A non related question. If I pre-render the passes using the LC retrace option and than send the files to a V-ray 1.5. render farm, will it render correctly? Does the retrace occure during the final calculation, or is stored directly in the LC?

[vlado]

If I pre-render the passes using the LC retrace option and than send the files to a V-ray 1.5. render farm, will it render correctly?

It should render correctly, yes.

Best regards,
Vlado