Noise in Raytrace Glass

Development Rendering
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1

Hello, Im doing a Scene with in Unreal 5 with Lumen for production, I want to render 4K BG for my VFX. But all the glass materials in scene are making a lot of noise.

If i use TAA as Anti-Aliasing, the noise dissapears, but because im rendering in 4K i have to activate the HIGH RESOLUTION option to split the image so my GPU doesnt crash, but doing this disables TAA and uses “none” as Anti-aliasing.

I tried changing the samples of the lights, in temporal sample count, in the PostprocessVolume but the noise doenst change at all

At first I thought that my glass material was wrong, so I downloaded the Archvis Project to test it there and still have the noise in the glass

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when i change the anti-aliasing looks perfect. There is a way how to render this without the noise?

2

With renderers in general. More rays = less noise.
You can probably change the render settings to have more rays.
But it sounds like you need a more powerful rig to computer the end result.

3

Im using a RTX 2060. I increased the samples in a lot of places, my elements looks better but everything that goes though glass is still noisy. With 1 or 64 samples in the lights still doesnt make any difference

Even I increased the setting in my Cnematic Camera to the top and still get a ton of grain in the refractions

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and increasing the temporal sample in the rendered option doesnt solve my problem

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4

In that scene i noticed, with regular raytracing, the one thing, that caused a lot of noise for me, was using “area shadows” in the Translucency tab. Using “hard shadows” for translucent objects got rid of all noise (reflections used area shadows). Raising the samples number there did nothing with area shadows, not sure why.

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Especially those images in the bottom right corner show a big difference, but it´s still noticeable on the glass bottle (mostly on it´s right side).

Other than that, maybe try the pathtracer with the denoiser, and in the motion render queue, try the spatial samples instead of temporal samples.

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5

… if you have time, try the nvidia branches that specifically deal with glass.
Maybe they got it right…

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6

Thanks for the information, in your scene you’re using NONE as your anti-alias?
If I use TAA the problem is fixed but I cant render 4K in TAA

I increased Spatial samples and there isn’t too much difference, i checked what you said about the type of shadow, and in Hard shadow I’m getting a black glass in my scene, but if i deactivate the shadows there is less noise. Give me the impression that even when i increase the whole scene the sampling, inside the refraction the scene has a sampling of 1.

Sadly in my scene I have a ton of decals for details and Pathtracer doesn’t render them

EDIT:

I turn off a lot of elements in my scene to find what is messing my scene. I foudn that one of my elements that uses emission is making a ton of noise in the glass

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for now i unchecked the Cast Shadow on that element and my glass is looking clean, i will keep reactivating my elements

7

Maybe this video here helps you with the pathtracer:

One importand node for glass is not in the video displayed (it was integrated later): the Absorption Node (for pathtracer only)
Here is the link to the manual for the Pathtracer, there you can find infos for the Absorption node too, f.e. for how to set it up.

Also, decals are not supported by the Pathtracer, but they will be supported with UE 5.1, according to the roadmap.

https://portal.productboard.com/epicgames/1-unreal-engine-public-roadmap/c/846-path-tracing-improvements

The Path Tracer continues to add support for more engine features, including:

Exponential Height Fog and Sky Atmosphere Fog

Decals

Single Layer Water

Per-instance custom data

Light functions

Multi-GPU rendering

In addition, we’re adding a new mode for more accurate motion blur in Movie Render Queue.

8

In 5.1 the path-tracer supports decals. Not sure if it’s worth pulling down an engine build, but it’s always an option.

And I know that issue, i was doing fidelity tests with 5.0 EA over a year ago, I ended up just turning decals into transparent quads and going from there.

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