Version Machinima 2021.1.1 - RealTime And Path Traced TEST - Water Effect Artifact in Path Traced

Dear friends, I have been doing more render tests.
The RTX real-time render is fine and has almost no image artifacts.
@pekka.varis as experimented and I agree that rendering with dlss and some parameters improves rendering in realtime.The realtime rendering is instantaneous and fast.

In my case, the RTX path-trace mode creates image artifacts that look like a basin of water, especially bounces and light reflections. I have gotten to raise the samples to 10 and the subframes to 100 and the effect does not disappear. There is hardly any difference even if the quality is better.

I don’t understand this annoying water effect.
By doing tests I have deduced that the culprit is “denoising”.
By having the denosing turned off or at its maximum value “1”, the treble effect disappears, but logically the scene is filled with noise.Let’s say that denoising creates a kind of blend.

I have rendered renders with denoising values ​​of 0,0.12,0.25,0,50 and 1. Less noise more water. More noise less water.

My conclusion is that I do not understand why it happens. Any ideas? Can you incorporate future changes to eliminate this water effect?

I incorporate an example video.
Note: Some image jumps are due to premiere. They do not exist in final machinima renders.

Thank you!

En Español:

Queridos amigos, he estado haciendo mas pruebas de render.
El render RTX real-time esta bien y no tiene casi artefactos de imagen.
@pekka.varis ha experimentado y coincido con el que el render con dlss y algunos parametros mejora el render en realtime.
El render realtime es instantaneo y rapido. En mi caso el modo RTX path-trace me crea unos artefactos de imagen que parecen baalsa de agua, sobre todo los rebotes y reflejos de luz.

He llegado a subir los samples a 10 y los subframes a 100 y el efecto no desaparece. Apenas hay diferencia aunque la calidad sea mejor.

No entiendo este efecto de agua tan molesto. Haciendo pruebas he deducido que el culpable es el “denoising”.

Al tener el denosing apagado o en su valor maximo “1”, el efecto de aguda desaparece, pero logicamente la escena se llena de ruido. Digamos que el denoising crea una especie de blend.

He realizado renders con valores de denoising a 0,0.12,0.25,0,50 y 1. Menos ruido mas agua. Mas ruido menos agua.

Mi conclusion es que no entiendo por que sucede. Alguna idea? Podeis incorporar cambios futuros para eliminar este efecto de agua?

Incorporo un video de ejemplo.
Nota: Algunos saltos de imagen, son debidos a premiere. No existen en los renders finales de machinima.



Thanks Antoni for these testings. What a laboratory!

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Hi Antoni, a quick update that we are looking into this - thank you for providing the great data and video!


P.S. I really enjoyed watching your film, Ma Belle!

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Hi @Edmar, thank you very much for your answer. And I’m happy that you liked Ma Belle !!
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A hug!


Hi Antoni,

thank you for this test. When you say water effect, do you mean the flickering in path traced mode? Could you send us this scene? There may be some settings that need to be tweaked a little to diminish that.


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Hi @slapere

Here you have the scene, with the props and materials.

I think flickering is the water effect. It’s the constant flickering and movement of the textures. With denosing at 1 or deactivated, the artifact is not seen, but logically it is all full of noise. Let’s see if it can be solved with some good parameters.

Thanks for the scene, I will investigate it.


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I tried a few things in your scene. Can you try these steps:

  • untick Enable Many-Light Sampling in Render Settings → Path Tracing → Sampling & Caching
  • set the Denoiser Blend Factor to 0.0 (equivalent to 100% denoising)

Please let me know if that improves the water effect issue.


hi @slapere

Here you have the render. It does not matter. The same effect of water or a kind of blur or watercolor movement. I don’t know how to define this artifact. You see it? You know what I mean?

With the scene I sent you this afternoon, can you create a render with the best possible quality, so that I can see the difference?

Hi Antoni,

I understand better now. This scene generates a lot of fireflies (very bright pixels) because of the semi-glossy floor and ceiling reflecting light paths. The artefacts you see are due to the denoiser trying to reconstruct a clean image from a noisy image containing many bright pixels. To reduce those artefacts, you will need to increase the number of samples per pixel per subframe.

I have rendered an animation of you scene with the following settings:

  • render preset: RTX path-traced
  • path trace samples per pixel (per subframe): 200
  • subframes per frame: 20
  • frame shutter open: -0.5
  • frame shutter close: 0.5
  • Optix denoiser blend factor at 0.0 (equals setting the denoiser at full strength)
  • I left many light sampling enabled to preserve the highlights

With these settings, most artefacts are gone.


I do not know is the floor meant to be semi-glossy, like water on the floor…
But now It looks really good to my eye! It looks like a parking lot that has been washed 10 min ago… Still some water left on floor.

But these kinda setings samples per pixel 200, gonna end up pretty slow rendering :/

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Hi pekka,

One thing we noticed is that this scene uses lots of small sphere lights, which may cause fireflies. I suggest to replace them with Rect Lights, it will remove a lot of fireflies a lot and as a result reduce the number of samples you need to get a noise-free render.

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Thanks @slapere for taking your time and sending me this test … The test is excellent and shows that with the right settings it is possible to eliminate strange defects.

The counterpart is as @pekka.varis says that the render is very slow. 100 frames (4 Seconds) has taken me 14 hours with my 2070 rtx. It is a long time. As you have indicated, I am going to test what happens without so many reflections and I will change the Rect lights to see if I can lower the render time.

Another idea is to render at 1280x720 to lower the time and then with AI programs like “Topaz Video Enhance AI” to scale to HD or 4K.

I continue with the tests and report.

Here you have an almost perfect render in real-time, which is very close to Path-traced.
I have touched all the real-time settings and have made the shadows, reflections etc look very good and that there are no strange artifacts. The best: Speed-Quality in one. It’s in HD, now I’m going to try scalar with topaz.
Here you have the settings file in case you want to import and test it.

File Settings;
RTX_Realtime_Scene_Settings.settings.usda (1.6 KB)

Load Settings:

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Thanks Antoni!

I tried these with the scene I am currently studying with.
Antoni RTX RTX Real-Time settings
0.60 sec. / frm render time

Default RTX Real-Time settings
0.14 sec. / frm render time

Your settings have brighter overall look, even the ambien light intensity was 0 - compared to the default 0.22 - Do you know what makes it brighter?

I think there is somehow sharper feel with your settings…

Hi Antoni,

Looks great! Glad to see you were able to get close to PT quality in real-time mode. Increasing the AO ray length and adding some indirect diffuse GI (and disabling ambient lighting) really helps to increase realism.

Looking forward to more of your renders!


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You can increase the brightness with tone mapping and color correction in the Post Processing settings (under the Render Settings tab).

There are a ton of post processing options to experiment with: for example you can add bloom, chromatic aberration and vignetting (under TV Noise & Film Grain) which helps to convey a more cinematic look.