VRay RT w/ custom lights

[jeremyp]

Is there a way to notify RT that a custom light has changed?

Our light rig uses all custom lights which are created in the post scene translate script. We would like to use RT much more than we currently do (hardly ever).

[yolov]

I don't think this is currently possible, the post-translate gets executed only once and changes there are not detected. It can turn out to be a very difficult thing to detect those changes and it will be prone to a lot of issues and crashes as I imagine it.

I suppose the problem is that on IPR start, the lights are there but the first change removes them from the render?
If yes, then you can do a vrscene export with your post-translated lights (and nothing else from the maya scene), import that as a vrayScene node and render like that. This will keep the lights in the scene.
Will that work for you?

[jeremyp]

No the problem is that they don't update.

I imagine a system where the in memory RT scene can be modified by python commands like vray.utils. Just need to know which node to update (eg findByName), and wouldn't need to create anything new just changing the params of nodes.

[yolov]

Just to make sure I understand you correctly - can you describe your workflow in a bit more detail, please?
You're adding lights with post-translate? Or modifying existing ones with post-translate?
What changes do you expect to make to the post-translate-created lights with IPR?

I think what I so far understand is that you're creating lights with post-translate, but you want to make changes to the post-translate script itself and you want *that* to be updated in IPR, am I correct?

[jeremyp]

Yes, the lights are generated at render time (via post translate) from a rig in Maya. So we want a way to update the IPR when changes to the light rig are made.

I didn't see this as re-running the PTS (though that may work) but a system where changes are communicated to the IPR. E.g. vray_ipr_set_param(vray_node, value)

[yolov]

I think it would require re-running the post-translate script. The problem right now would be that on the first start, the script is executed, then if you make changes to the scene in IPR, it would be as if the post-translate has never been executed after the first change. If you think that this would be better, I will pass it on to the devs as a request. This would make everything in the post-translate stay in the IPR session, but you won't be able to make changes to the script itself while IPR is running.
Also, keep in mind, that this sounds like something that's very prone to errors and might be very unstable, so we might decide to not do it for safety reasons.

[jeremyp]

I would think that the post translate script is only run when the scene is rebuilt. So we are only talking about modification of parameters of the existing scene which is currently in the IPR, say if I move a light or change it's color. It's something that would allow use to use IPR. Not sure why that would make it more unstable?

[yolov]

It would be (potentially) unstable as the changes to the scene progress - deleting objects in IPR etc.
I'll pass this on to the devs for consideration.

[t.petrov]

Currently this isn't possible and updating the V-Ray scene in IPR is tricky business. We could probably provide some way to update plugins created by post-translate scripts, but then you'll need to implement the change detection mechanism we're already implementing. And this is even more complex and error prone. The real question is why you need to create lights using post translate. Is there something we can do in the UI/node api which would make it possible to achieve the same thing using just nodes?

[jeremyp]

We have a light rig that abstracts the user from the creation of renderer specific lights. The renderer specific lights are generated at render time, in this instance via post translate but they could be generated into the vrscene outside of maya.

[yolov]

If you export the lights to a vrscene and bring it back as a VRayScene object inside maya - this will stay withing the IPR session, unlike the post-translate script.

[jeremyp]

If you export the lights to a vrscene and bring it back as a VRayScene object inside maya - this will stay withing the IPR session, unlike the post-translate script.

Yes interesting. Though are updates to the vrscene supported by IPR?

[yolov]

I forgot the 'changes to the light rig' bit.
Is the light rig changed outside the current Maya session? I.e. one artist loads the light rig and does changes to other parts of the scene excluding the light, but then another artist changes the light rig on his workstation and sends the update over?