Hair artefacts when rendering with MRQ

Development Rendering
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Hello there :slight_smile:

I have an issue with artefacts (only) when rendering with the movie render queue:

The flicker is mostly visible in the tail area. I have debugged for a long while but I just can’t find the problem. It doesn’t seem to be related to DOF, or the lights, or the HDRIBackdrop I’m using. This is using lumen but I get this also without.
I played with the AA settins without avail and I tried what’s suggested here without luck:

The weird thing is that I don’t get these artefacts when playing this in realtime, only when rendering a movie.

I’m not an unreal expert and maybe I missed something super obvious. I’m be super grateful for any hints you might have! :slight_smile:

Thanks in advance!!

seb

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What’s your current AA setup?

The real-time viewport uses Epic’s Temporal Super Resolution (TSR), which you can think of like FSR2 or DLSS. It’s an upscaler and denoiser that handles many kinds of game phenomenon quite well, and it’s relatively good at dealing with hair and fur imo. If the viewport has no issues but the MRQ does, perhaps MSR is just doing a very good job denoising the hair aliasing, but is disabled for the MRQ?

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Hi!

Thanks a lot for the reply!

I was actually overriding it to None and increased spacial samples because I saw in some tutorials that this would give the best results…

I have now tried to set it to TSR as you suggested but that sadly does not give the same result as the viewport.

I’ve attached a capture of the viewport here:

There is still some slight flickering noticable but it’s still much better than in the queue render.

I’ve tried to increase spacial and temporal samples with TSR but that also didn’t change anything :confused:

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@jblackwell It was DOF after all… The root of the artefacts seem to be thin darker hairs over the bright ground, getting blurred.
I can alleviate the problem by making the hairs a bit thicker or bringing them more into focus (or making them brighter :smiling_face_with_tear:).
I’m still confused by the discrepancy between MRQ and realtime. I thought it might be the fps (rendering at 24 fps vs 90fps in the viewport) but it doesn’t seem to make a difference.

Out of interest, if I don’t override anything with a MRQ AA setting really all values are kept the same or are there differences that inherently apply when rendering with MRQ?

Thanks for your insight!

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Honestly the DOF+hairs make a lot of sense. I’m not going to pretend to understand fully how UE’s transparency system works, but I understand experimentally that mixing DOF+translucency+anything subpixel (like hair) generally leads to a bad time. I have no idea what the viewport vs. MRQ cause could be as well, but if you have the juice, you could probably use the path-tracer with simulated DOF to alleviate the issue entirely. Happy to help :slight_smile:

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