Any way to stop/resume render maintaing consistency with Niagara and light effects?

[papillon68]

I have a quite long render, 8K@60fps and I’d like to stop the render and later resume from the last position.
The problem is that when resuming the render (so, next day I restart UE, load the render queue and set next frame batch), both Niagara particles systems and light functions will not get re-started from last “good” position and so there is no consistency between the last rendered frame and the new one. They basically get re-calculated from frame 0.
In Niagara systems I’m using the “deterministic” option enabled and a fixed seed, but that doesn’t seem to do the trick.
Any suggestion?

[comlys (Shaun Comly)]

You would want to cache as much as possible in Sequencer. Thats the only thing that is really guaranteed. If you don’t want to do that you can use warmup frames to get your effect back to that frame but really caching in Sequencer is your best bet.

[papillon68]

Thank you very much, really appreciated. I found some tutorials about caching Niagara systems in sequencer. How about caching a light function (driven from a 3D noise texture for example).
Is there a way to cache that too?

Just to clarify, in the material that is used for the light function, I’m using a parameter that is keyframed in the sequencer; so basically that parameter is 0 at frame 0, and 100 at the last frame.
That way, the “seed” for the panner time input is not random.
Unfortunately, it doesn’t work as expected: if I stop the render and later resume it from a certain point, the frames are not matching as expected. I can’t understand why.

[papillon68]

I found out that having automatic exposure on the camera enabled would actually cause not only different brightness calculations over time (which was kind of expected), but also interfere with how the light function material works. I’m not sure why that is but switching to manual exposure is now finally having light function working like I wanted.