why does Maya hang when finishing a render?

[Richard7666]

Some scenes it seems to be worse than others. I often find V-ray will hang (worst case: freeze Maya entirely) for several minutes after a render finishes or is cancelled.

[2013/Aug/23|13:01:19] V-Ray: Number of raycasts: 111992098
[2013/Aug/23|13:01:19] V-Ray: Camera rays: 3406989
[2013/Aug/23|13:01:19] V-Ray: Shadow rays: 96317222
[2013/Aug/23|13:01:19] V-Ray: GI rays: 11934188
[2013/Aug/23|13:01:19] V-Ray: Reflection rays: 4610351
[2013/Aug/23|13:01:19] V-Ray: Refraction rays: 2623773
[2013/Aug/23|13:01:19] V-Ray: Unshaded rays: 0

^I get that, then it all just freezes up. Maya 2013, V-ray 2.30.01
Does anyone have any ideas?

[tashko.zashev]

Hi,

Could you please provide more detail about this issue.
Do you render locally?
Do you have many textures in this scene?
Is it scene dependent?
Could you open the Task manager and check the CPU and Memory usage when Maya hangs?

[CAPTURE_MM]

Does this happen if you render batch or in vray framebuffer?
If it happens while using the framebuffer maybe u should mark "Don´t save image (ignored in batch mode)" in the vray Common tab under Image File Output.
Saving the image and all it´s render elements can take quite some time.
Even if you are rendering previews the image and selected render elements get written to the tmp folder of your output directory.

[Richard7666]

VFB, rendered locally, maybe 40 different textures ( including reflection, bump etc). Some scenes are worse than others.

I do have a lot of render elements and am rendering to exr...

I'll try the above suggestions

[Richard7666]

Hmm, none of that seems to have helped. Looking at Windows' task manager, I see my RAM usage dropping down over the course of several minutes before Maya unfreezes, as though V-ray is unloading everything (textures?) from RAM or something.

Doing test renders is currently a nightmare

[yolov]

Have you experienced this behavior with other V-Ray versions?
At the end of a render, V-Ray will unload all assets (textures included) from RAM, which can take a while if you have gigabytes worth of assets.
Additionally, if you're rendering at high resolutions (e.g. 3-4-5K by 3-4-5K or more) AND have lots of render elements, V-Ray will have to write out all this information to file. So the more textures + the more render elements + the higher the resolution, the longer it will take to finish the frame. We've done some optimizations over time to improve this, but in cases such as this it will always take some time to finish up the render.

What you can do to compare is disable the render elements, render a layer override with no textures or disable the file output. Of course, a sample scene will always be useful to check if there's something wrong.
You could also try the nightly builds, there is a chance that some optimizations (not deemed stable enough) haven't made to the stable release.

[brainspoon]

Hi,

I just encountered the same problem. During batch rendering it hangs before saving the first file. This is the last output I get.

[2014/Mar/10|12:30:07] V-Ray: Number of raycasts: 592525955
[2014/Mar/10|12:30:07] V-Ray: Camera rays: 10414319
[2014/Mar/10|12:30:07] V-Ray: Shadow rays: 77289736
[2014/Mar/10|12:30:07] V-Ray: GI rays: 405070216
[2014/Mar/10|12:30:07] V-Ray: Reflection rays: 0
[2014/Mar/10|12:30:07] V-Ray: Refraction rays: 0
[2014/Mar/10|12:30:07] V-Ray: Unshaded rays: 100505294

[svetlozar.draganov]

As Alex pointed out above the most likely reason for the hand/slowdown is assets-unloading. Vray needs some time to free the memory occupied during the rendering and this process is not instant especially for very heavy scenes. However it would be a good idea to update to the most recent official release or to the latest Nightly build since there were some improvements on that matter.
You could also send the scene along with all external assets for investigation. FTP could be provided if needed.

[Neilg]

Watch the folder you're saving files to - if it's saving 20 50mb exr's, that's why it's busy.

[Rens]

I've always noticed this when rendering with Maya compared to with Max. In Maya it takes much longer to unload when you have lots of textures and displacement.

Just out of curiosity, why does it need to be unloaded like this, would it be also be possible to 'kill' it and free it quicker, or would that be too messy or not possible?

[vlado]

V-Ray 3.0 for Maya has an option to not unload textures. In that case it does complete the render a lot faster.

Best regards,
Vlado

[Rens]

Very nice!

[Richard7666]

out of interest, what are the downsides to not "unloading" it?

[yolov]

it keeps the textures in the RAM in the meantime