velocity pass with vraymesh (proxy) issue

[albertoluceno]

Hello,

We're trying to standardize the use of VRay's velocity pass together with Nuke's vectorBlur node for a current production and were encountering an issue.

Attached you will find three versions of frames 69, 70 and 71 of a shot we're working on:

- first is the beauty render of each frame
- next is the velocity pass of that same render
- finally, is the result of the vectorBlur

As you can see the behavior of the velocity element is strange in frame 70 (it changes dramatically from the others and has strange lines that don't seem to correspond to the geometry) and the result of the vectorBlur has artifacts.

This kind of problem repeats itself sporadically ruining the workflow.

We are hopping somebody might identify what is causing this and perhaps offer a solution since vectorBluring with the velocity pass would certainly be the most efficient workflow for us.

We think this has to do with the fact that our objects are proxies. But we have created the proxies exporting animation and don't know what else to do...

We would really appreciate any help on this one.

Cheers,

Alberto Luceño - El Ranchito Imagen Digital

[gardeler]

i have not seen that before, but a wild guess could be wrong frame rate in the proxy? I read in the manual that a proxy can store frame rate in it. Is there any similarity between the failing frames? (like 24 frames in between.) What is the motion of the palm tree in the shot?

[vlado]

Does it always happen on the same frame? Would it be possible to get us the relevant files to reproduce the problem to vraymaya@chaosgroup.com?

Best regards,
Vlado

[albertoluceno]

Bad news,

It seems to happen randomly. And what's worst: it isn't the same proxy that is giving the problems; sometimes it's one, sometimes it's another.

The vraymesh files are quite big, hundreds of mb, so it isn't going to be easy to send them to you.

Thanks for your help,

Alberto

[vlado]

Ok, if it's random then at least the right velocity information is in the file.

Can you tell me which V-Ray build you are using? Without the scenes is hard to figure out what is happening. We can get you our ftp info to upload an example scene if it is too big.

One more question; have you changed the playback speed for the proxy?

Best regards,
Vlado

[albertoluceno]

No, we're using a playback speed of 1. Although we are using the start offset.

We're using version 1.50 SP1

You can e-mail me the ftp details to alberto@elranchito.es if you want and I'll upload one of the proxies

Thanks again,

Alberto

[vlado]

Ok, I will get the support guys to send you the FTP infos.

Best regards,
Vlado

[Metzger]

Create an animation of the tree that is greater 1000 frames, then don't offset past 1000 or before 1. My guess is that the motion blur is jumping from the proxy cycle which is causing the artifacts.

No, we're using a playback speed of 1. Although we are using the start offset.

We're using version 1.50 SP1

You can e-mail me the ftp details to alberto@elranchito.es if you want and I'll upload one of the proxies

Thanks again,

Alberto

[vlado]

Hm, this should not be an issue; the velocity is baked when the proxy is exported, so it shouldn't matter if frames jump around.

Best regards,
Vlado