Reproducibility of rendering results

[Holger Kr]

Hi,

I have a question. Is it somehow possible to get rendering results reproducible on different hardware (GPU/CPU)?

For example I have a scene being rendered on my notebook (with NVIDIA MX150 GPU). I take the same scene on the same version of UE 4 on my PC (GTX 1070, AMD Ryzen) and I see small differences. If I make a screenshot of both and put them into photoshop, digitally subtracting one from each other, I see a lot of minor differences.

Is it in any way (by modification of the project and engine settings, by omitting certain rendering effects, etc.) possible to achieve the same exact image?

Background is that I try to use these images to train neural networks and these differences may not be problematic for the eye but for the results of the network training it is.


Any feedback on that is appreciated!

Regards,
Holger

[Raildex_]

Disable Temporal AA. It is calculated over multiple frames and can have variations depending on the framerate

[darthviper107]

It also depends on what other things you're using, some things are always random (like particles)

[Holger Kr]

Disable Temporal AA. It is calculated over multiple frames and can have variations depending on the framerate

Thank you, that is a good hint.

[Holger Kr]

It also depends on what other things you're using, some things are always random (like particles)

Ok, sure I see the point. Are there other effects which use the basic principle of randomization? Particles is surely one of them but I try to track down every one of them.

Your feedback is welcome!

[Manoel.Neto]

A bunch of effects use randomized noise or jittering to work. Screen space reflections, screen space ambient occlusion, motion blur, DOF, and temporal AA, off the top of my head. There's also the obvious-named camera noise, which I don't remember if is enabled by default. Get into the post process volume and disable them all.

Keep in mind you can still get subtle changes imperceptible to naked eye across different GPU models. The only way to get a truly identical image would be using a software renderer, but I don't know if UE4 can be forced to use the Direct3D REF rasterizers or Windows 10's WARP rasterizer (but WARP may not be deterministic since it's designed for performance).