various bugs with vrscene export

[frueter]

Hi,

I have been battling with exporting a vrscene file from Nuke to render standalone vid Deadline. After several hours of debugging I found the following and thought I'd share to save others the pain.
Note that this is with Nuke 10.5 and VRay 3.60.05, so some of this may already be fixed (waiting for a project that finally justified me upgrading).
When exporting a vrscene file:

1. ...VRayMtl2Sided nodes must have both "front" and "back" pipe connected, otherwise the resulting vrscene file might have some corrupt value for the input paramter causing the vrscene import to fail.
2. When using a VRayCamera's "read from nuke camera" option, the resulting vrscene will have the default values instead of those from the respective Nuke camera.
3. If a light's intensity or colour parameter is animated (even a single key frame), it will produce the wrong exposure in the vrscene file. Looks like the only workaround is to leave the light's exposure static and instead render a flicker texture to project.
4. Deadline issue: Deadline's path swapping does not affect texture paths in the vrscene file. Fair enough I gvuess, but I have logged a feature request to parse ascii vrscene files and save a temp version with the applied path swapping and pass that to VRay for a soncistent workflow. In the meantime I have set up Switch nodes in Nuke to switch between VRayTexBitmap nodes with the required file paths (one for interactive, one for rendering). I cloned the Switch node anywhere I use textures, then I added a pre-render callback to the VRayTranslator node that flicks the Switch node(s) to the render path input. Another post-render callback switches them back to the correct path for my interactive session (e.g.: nuke.toNode('FOR_VRSCENE_EXPORT')['which'].setValue(1) where "FOR_VRSCENE_EXPORT" is the cloned Switch node)

Cheers,
frank

[frueter]

egg on face:
The Deadline issue was user error as I was not aware that I had to enable path swapping for vrscene files in the plugin config. So ignore the last point.

[georgi.zhekov]

Hey Frank,

We have reproduced the problem with the 2Sided material, but the other two (the V-Ray camera and the light intensity) seem to be working fine here on a simple scene.
Can you send us some scenes so we can check what is going on?

Thanks!

[frueter]

Hm, interesting. Is this with the same old version I am using or the latest one? I am also hvaing issues with exporting an animated alembic from Modo which always ends up statis in the vrscene file. I have sent an example set to support but havern't heard back. I wonder if it's simply a version issue?!

[frueter]

Hi Georgi,

thanks for checking!
I can't produce the camera bug anymore either, but a keyframes light still does not produce the right exposure when exported to vrscene, at least not in my old version.
Attached is an example that fails for me (e.g. check frame 40).

Cheers,
frank

[georgi.zhekov]

Can't reproduce it in here I'm afraid, tested this with both V-Ray 3.7 (the one from here - https://download.chaosgroup.com/?lic...109&product=47) and V-Ray Next under Windows and Linux.
Works in both animation and single frame.

What I did was to open the scene, export the vrscene and render it through the Translator node. The result from Standalone matches the one in Nuke.
Could it be that you're using an old nightly build? Can you show us how it looks with some images?

Cheers!

[Christophe.Cot]

Hi Frank,
In the test setup, I notice you export one vrscene per frame. Nuke can be very tricky with all its internal hash-based node cashing and as a result would skip calling some essential setup in our code. This scheme is a pain to workaround.
Especially on this topic, I have personally never tested nor though of exporting an animated vrscene as individual vrscene using the frame specifier syntax, and somehow I would be surprised if it works fine.
Isn't it possible to export the scene as a single animated vrscene file instead ? If so, do you have the same problem is that case ?
Note that while usually it should not be required it is also possible you would need to check the Each Frame knob on the translator to prevent yet some other unexpected optimization of the Nuke DAG causing missing frame.

[frueter]

Thanks guys, I was on V-Ray 3.6. I have updated to use the link Georgie posted and when exporting a single vrscene file it seems to work now. Still seeing od behaviour when exporting a sequence, in fact when exporting frames 1-10 I only get frames 1-3 on disk for some reason.
I had to hack it with python to get the full sequence:

n = nuke.toNode('VRayTranslator1')
for f in xrange(1,11):
    print f
    nuke.execute(n, f, f, 1)

However, exporting to a single frame now work in 3.7 so I can use that.
Thanks guys!

frank