Why does the scene scrub when launching a DR render

[SonyBoy]

I'm pretty sure this wasn't the case a decade ago, but now when launching a batch render into the VFB, the scene scrubs all the way through the specified frame range.

I had previously thought this was related to GI, but I'm now doing some low quality renders without GI and noticing this still happens.

What is going on with this, why is it necessary, and is there a way to disable this behavior which can often take several minutes to complete.

My understanding of how DR works may be wrong, but I've always assumed the host machine is simply farming out buckets to other machines' CPUs to calculate, so it's a mystery to me why it should be necessary for the whole frame sequence to first scrub like this. There are no dynamics in my scene.

[hermit.crab]

Before "farming out" buckets to other machines, it writes a DR .vrscene file, then goes through the timeline and updates the frames so as to append them to the .vrscene. I guess the annoying part on your end is that it happens even without dynamics in the scene. But maybe there's something more to it. I'll contact the devs to get more info and write back.

[SonyBoy]

The point is that this timeline scrubbing only occurs with DR, so it's obviously related to that. But I can't see why the slave machines would need to know what's coming in the entire timeline before being able to assist in rendering the current frame. Perhaps there is a setting that can be toggled to stop this?

[hermit.crab]

Are you rendering animation? There's a "Run dynamics before animation start" that goes through the whole timeline prior to rendering. Maybe you have it on? Also, when rendering animation, V-Ray exports a .vrscene for the whole range to send to the slaves, otherwise, it would have to do it on every frame.

Just to be sure that we're talking about the same thing: Mind if you share a video of the timeline scrubbing?

[SonyBoy]

Yes, I'm rendering animation. There are no dynamics in the scene, as I stated, so even if Run Dynamics Before Animation Start is enabled, this shouldn't be affecting anything. In any case, that setting is not enabled. You seem to be going around in circles with my query, since the whole point of my confusion is that so far as I understand the slave machines should not even need the entire scene, let alone the entire timeline, to assist with rendering. And I'm sure this wasn't previously the case. The master machine simply sends buckets to the CPUs of the slave machines, which return the calculations to the main render process.

Perhaps that is simply not how it works?

[hermit.crab]

so far as I understand the slave machines should not even need the entire scene, let alone the entire timeline, to assist with rendering. And I'm sure this wasn't previously the case. The master machine simply sends buckets to the CPUs of the slave machines, which return the calculations to the main render process. Perhaps that is simply not how it works?

Of course they do. The master machine only assigns buckets (regions to render) to the slave machines. For the servers to be able to render them, they need the scene (in Maya - .vrscene; in 3ds Max - .max scene) and the assets (directly or via a common path). Afterward, the master machine combines the results to get the whole image. More info in the docs page here.

[SonyBoy]

OK, still doesn't explain why the timeline would need to scrub.

[hermit.crab]

Because the exporter goes through every frame so as to write them in the .vrscene (even if there are no dynamics or anything keyed). This happens when manually exporting an animated. vrscene (Export to a .vrscene checkbox), too, not only with DR. Happens in f.e. 3ds Max as well.

[SonyBoy]

As I have made very clear several times, that is simply not the case. This scrubbing occurs ONLY when using DR. When DR is turned off, the first frame of the sequence will start to render immediately. Thus, the scrubbing is being caused by utilizing DR.

[hermit.crab]

As I have made very clear several times, that is simply not the case. This scrubbing occurs ONLY when using DR. When DR is turned off, the first frame of the sequence will start to render immediately. Thus, the scrubbing is being caused by utilizing DR.

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[SonyBoy]

I don't know what this is.