All renders have slight graininess (both Eevee and Cycles) #113719

New Issue

TomSpicer · 2023-10-14T14:34:48+02:00

TomSpicer commented

2023-10-14 14:34:48 +02:00

System Information
Tested on Asus Rog G752VS
Operating system: Linux Mint 21.2
Graphics card: NVIDIA Corporation GP104BM [GeForce GTX 1070 Mobile]

Blender Version
Broken: 3.6.4 (2023-09-25 13:24), Blender 4.1.0 - Alpha ( October 13, 16:03:29 , 4050b0d6df )

Any render has graininess (high frequency inconsistent pixel brightness), also with Eeevee, even rendering just a background or an emissive plane with no lights in the scene.

Exact steps for others to reproduce the error

With a default startup, change the background color to something like (0,1,0) to make the graininess clearer when enhancing the rendered image in an image editor.

Problem seems absent when using "AgX" for "Viewport transform" in Blender 4.1.0 - Alpha ( October 13, 16:03:29 , 4050b0d6df ) but present for other modes and all modes from older Blender versions.

To see the graininess with a naked eye, you'll need to enhance the image, like in GIMP as illustrated.

**System Information** Tested on Asus Rog G752VS Operating system: Linux Mint 21.2 Graphics card: NVIDIA Corporation GP104BM [GeForce GTX 1070 Mobile] **Blender Version** Broken: 3.6.4 (2023-09-25 13:24), Blender 4.1.0 - Alpha ( October 13, 16:03:29 , 4050b0d6dfdb ) Any render has graininess (high frequency inconsistent pixel brightness), also with Eeevee, even rendering just a background or an emissive plane with no lights in the scene. **Exact steps for others to reproduce the error** With a default startup, change the background color to something like (0,1,0) to make the graininess clearer when enhancing the rendered image in an image editor. Problem seems absent when using "AgX" for "Viewport transform" in Blender 4.1.0 - Alpha ( October 13, 16:03:29 , 4050b0d6dfdb ) but present for other modes and all modes from older Blender versions. To see the graininess with a naked eye, you'll need to enhance the image, like in GIMP as illustrated.

render - emissive plane - enhancing in gimp 2.png

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render - background.png

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render - background - enhancing in gimp.png

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render - emissive plane.png

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test.blend

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render - emissive plane - enhancing in gimp 1.png

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render - emissive plane - enhancing in gimp 2.png

render - background - enhancing in gimp.png

render - emissive plane - enhancing in gimp 1.png

TomSpicer added the

labels 2023-10-14 14:34:49 +02:00

Alaska commented

2023-10-14 15:41:56 +02:00

Blender applies dithering to the imageby default to reduce banding. This may be the issue you're experiencing.

To turn off dithering:

Open the Properties Editor.
Go to the Output tab.
In the Post Processing tab, turn dithering down to 0.

Does this help/resolve your issue?

Blender applies dithering to the imageby default to reduce banding. This may be the issue you're experiencing. To turn off dithering: 1. Open the Properties Editor. 2. Go to the `Output` tab. 3. In the `Post Processing` tab, turn dithering down to 0. Does this help/resolve your issue?

Alaska added

Status

Needs Information from User

and removed

Status

Needs Triage

labels 2023-10-14 15:42:06 +02:00

TomSpicer commented

2023-10-14 15:51:16 +02:00

Blender applies dithering to the imageby default to reduce banding. This may be the issue you're experiencing.

To turn off dithering:

Open the Properties Editor.

Go to the Output tab.

In the Post Processing tab, turn dithering down to 0.

Does this help/resolve your issue?

Why yes, you seem to have found the feature which causes the issue: setting dithering to 0 does seem to eliminate the graininess. However, I don't think this should be happening even with having default dithering. Dithering shouldn't impact flat colors. For example if only a single color background is rendered, or a flat plane with a single color emissive material like here, there's no two or more distinct colored pixels involved which a dithering filter would convert to a grainy noise for banding removal purposes.
So it seems to me like dithering filter code has a bug or limitation to properly deal with flat shaded features in the render: one may want to have dithering On for it to be applied to any gradients in the render, while also needing to have flat shaded features in the render, without one impacting the quality of the other.

As a reference, I'm providing all the dithering methods the image editor GIMP has. Out of all the options, only "Random" seems to add random graininess to flat colored features. Maybe Blender is using a similar algorithm, but I'm not sure why, something like Floyd-Steinberg or Blue Noise seems to make more sense.

> Blender applies dithering to the imageby default to reduce banding. This may be the issue you're experiencing. > > To turn off dithering: > 1. Open the Properties Editor. > 2. Go to the `Output` tab. > 3. In the `Post Processing` tab, turn dithering down to 0. > > Does this help/resolve your issue? Why yes, you seem to have found the feature which causes the issue: setting dithering to 0 does seem to eliminate the graininess. However, I don't think this should be happening even with having default dithering. Dithering shouldn't impact flat colors. For example if only a single color background is rendered, or a flat plane with a single color emissive material like here, there's no two or more distinct colored pixels involved which a dithering filter would convert to a grainy noise for banding removal purposes. So it seems to me like dithering filter code has a bug or limitation to properly deal with flat shaded features in the render: one may want to have dithering On for it to be applied to any gradients in the render, while also needing to have flat shaded features in the render, without one impacting the quality of the other. As a reference, I'm providing all the dithering methods the image editor GIMP has. Out of all the options, only "Random" seems to add random graininess to flat colored features. Maybe Blender is using a similar algorithm, but I'm not sure why, something like Floyd-Steinberg or Blue Noise seems to make more sense.

dithered - bayer.png

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dithered - random.png

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gimp dither settings.png

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original.png

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dithered - blue noise.png

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dithered - floyd steinberg.png

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dithered - arithmetic add.png

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dithered - arithmetic xor.png

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ugorek commented

2023-10-14 19:21:27 +02:00

I also noticed this strange pattern in my renders and had no idea where it came from or how to get rid of it. Turns out it was render.dither_intensity, thanks.

I also noticed this strange pattern in my renders and had no idea where it came from or how to get rid of it. Turns out it was `render.dither_intensity`, thanks. ![1.gif](/attachments/c72a3655-f09b-4ef9-9628-839184a82e76)

1.gif

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TomSpicer commented

2023-10-14 19:28:56 +02:00

I also noticed this strange pattern in my renders and had no idea where it came from or how to get rid of it. Turns out it was render.dither_intensity, thanks.

Sounds like a relatively new feature that has been aded and enabled silently , I don't remember this artifact before.

> I also noticed this strange pattern in my renders and had no idea where it came from or how to get rid of it. Turns out it was `render.dither_intensity`, thanks. > ![1.gif](/attachments/c72a3655-f09b-4ef9-9628-839184a82e76) Sounds like a relatively new feature that has been aded and enabled silently , I don't remember this artifact before.

Alaska added

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All renders have slight graininess (both Eevee and Cycles) #113719