Red pixel errors in renders

Screenshots from Windows showing red pixel problem:
red pixels.jpg
zoomed.jpg
 

Axis3d

Lightwave User Since 1990
Right... Ive managed to whip together the scene with a simplified stand-in object that is producing the same red pixels.

Hopefully this attachment of the scene works....

The HDRI is too big to be included and will need to be grabbed from the Wetransfer link above

Screenshots of Mac vs Windows scene to follow soon.
I'm not seeing any red pixels in either the 2019 or 2020 render. When I loaded the scene into 2019, I had to manually set up the HDR image in the Textured Environment. I'm on a Mac also, if that rules out anything.
 

Attachments

  • LW_2019_01.jpg
    LW_2019_01.jpg
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  • LW_2020_01.jpg
    LW_2020_01.jpg
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slacer

Member
I'm not seeing any red pixels in either the 2019 or 2020 render. When I loaded the scene into 2019, I had to manually set up the HDR image in the Textured Environment. I'm on a Mac also, if that rules out anything.
I got the red pixels as well on my Windows machine.
 

slacer

Member
I'm not seeing any red pixels in either the 2019 or 2020 render. When I loaded the scene into 2019, I had to manually set up the HDR image in the Textured Environment. I'm on a Mac also, if that rules out anything.
You have white pixels in your 2019 image.
 

Attachments

  • white_dots.PNG
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@slacer thanks for running the tests - confirming you also got the red pixels out of a Windows render. Was that with 2020 Im assuming?

@Axis3d in 2019 you would have to manually "rebuild" the HDRI environment setup. I ended up with those same white noise specs when testing this in 2019.

Interesting that you also dont get the red pixels on your Mac 2020 render.
 

Axis3d

Lightwave User Since 1990
You have white pixels in your 2019 image.
I rendered the still with the original settings from Scott.

On this still, I checked "Enable Mipmapping" in the Render Properties.

I also noticed that the fins and body of the rocket had its Reflection Options set to Rayrace & Backdrop. I changed that to Raytrace only.

I also set the Reflection Samples to 4 in the Render Properties tab.


The white pixels were from the 'normal' specular noise workflow. But there were still no red pixels in the renders.
 

Attachments

  • LW_2019_02.jpg
    LW_2019_02.jpg
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Last edited:

Kryslin

Active member
It appears to be a camera / render settings issue.

Using the provided scene, I found the issue, the two red pixels.
I made it go away by setting the adaptive threshold to 0.05.

The default value of 0.01 is too low to have any benefit; It's usually a good idea to set it to between 0.05-0.10. I typically use 0.07.

Enabling despike and giving it a value of 0.2 also removes the problem.

Using GPU denoising makes it worse. I suspect you've got a pretty high dynamic range on your hdr lightprobe image.

It appears that the simplest solution would be to enable despike (found on the render properties -> Render tab) and give it a tolerance of 0.02.
 
It appears to be a camera / render settings issue.

Using the provided scene, I found the issue, the two red pixels.
I made it go away by setting the adaptive threshold to 0.05.

The default value of 0.01 is too low to have any benefit; It's usually a good idea to set it to between 0.05-0.10. I typically use 0.07.

Enabling despike and giving it a value of 0.2 also removes the problem.

Using GPU denoising makes it worse. I suspect you've got a pretty high dynamic range on your hdr lightprobe image.

It appears that the simplest solution would be to enable despike (found on the render properties -> Render tab, and give it a tolerance of 0.02.
Thanks Kryslin

Out of interest... have you rendered more than one frame or the entire sequence?

When I was tinkering with settings it would often look like I had solved the problem and the red dots had gone, but in reality they just werent visible on that particular frame anymore and had occured later in the sequence.

When I render out the full sequence and play it back, the red specks appear randomly and "sparkle" along the surface.

Just wondering if your fix has solved it completely or just in the frame you were looking at
 
Yes, this was tested with LW 2020.0.3
@slacer - thanks for this! I didnt even know 2020.0.3 was out... Im still on 2020.0.2

interesting that its still happening in .3 and only on Windows

...but definitely looking like its to do with the HDRI image which i created. I did all the test renders and setups on my Mac, and Ive only come across the issue now when doing final renders on my beefier Windows machine.
 

Sensei

TrueArt Support
I have pink color dots:
Grab 1.png

Clicked on pink dot and pressed LMB:
Grab 2.png


Red channel has 201 millions percent...

Changed Brightness of Environment to 1%. It revealed that there are at least two pixels with too large values:
Grab 3.png
 
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