New technique to denoise noisy Mandelbulb3d images

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Offline Fraktalist

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« on: January 24, 2018, 05:46:53 PM »
I just read this great discovery by Julius Horsthuis on Facebook, great Info, so I mirror it here for those who don't use Facebook:

JH:"Rendering an animation with these parameters, I accidentally rendered extra frames with no moving camera.
Stacking these (40) redundant frames together is the ultimate denoising algorithm, making the transparency effect very convincing."

Question:" Curious, when you say you stacked them, do you mean in something like photoshop? Did the grain vary on each frame so it kind of averages and fills things out?"

JH:"Horsthuis Yes, the noise is different in each frame, otherwise it wouldn't work.
It could probably be done in Photoshop, but I used After Effects. I used the Echo effect, with 'add' function. Then an exposure to adjust the brightness back to normal"

Attached is the image.

All credits go to Julius who keeps pushing the boundaries!
« Last Edit: January 24, 2018, 07:38:14 PM by Fraktalist »

Offline 1Maniac

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« Reply #1 on: January 24, 2018, 05:52:48 PM »
Tips from a Master!!!

Offline claude

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« Reply #2 on: January 24, 2018, 06:11:19 PM »
Fragmentarium has had progressive rendering with multiple subframes that are averaged together for years.  You still need to design your script to make use of the subframe index to get any benefit, but the bundled Progressive2D does this, presumably th e 3D ray tracers do it too.  Would be cool if this rediscovery would be ported to the software to make it better for everyone.

Offline Fraktalist

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« Reply #3 on: January 24, 2018, 07:37:49 PM »
damn. and I still haven't had a close look at fragmentarium. just too many good programs and stuff to do - and only so little time.

thanks for pointing that out!
the whole concept reminds me of the buddhabrot technique.

Offline WAUthethird

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« Reply #4 on: January 26, 2018, 05:29:31 AM »
Ahhh, yes! Thanks! And I thought I was going to have to render all my frames in Monte-Carlo mode... :))

Offline Bill Snowzell

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« Reply #5 on: February 16, 2018, 04:21:22 PM »
Since the onset of digital imaging the astronomy world has been stacking raw frames for a few years including noise free dark frame subtraction. There is free software out there though it tends to use "raw" format camera  images though other formats could be used. I used to use a program called astro stacker in my stargazing days.

Offline fractal aesthetics

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« Reply #6 on: June 18, 2018, 05:06:35 AM »
To do this in photoshop:
1. Add the (almost) identical renders to a single file on seperate layers
2. Select all layers and convert to a smart object
3. Layer > Smart Object > Stack Mode > Median

This is very useful for reflections as they are often messy. You will need around 5 renders to really see a significant increase in quality. I'm not sure if this is more time efficient than just lowering the raystep multiplier, perhaps I'll do some testing...

Offline kohlenstoff

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« Reply #7 on: April 22, 2019, 06:04:48 PM »
This is very useful for reflections as they are often messy. You will need around 5 renders to really see a significant increase in quality. I'm not sure if this is more time efficient than just lowering the raystep multiplier, perhaps I'll do some testing...

Two layers can be enough. This can be useful if rendering time or motivation doesn't allow too much frames and lowering the raymarching step does not result in a desired outcome (many cool fractals do just dissolve when the step gets shorter).

1. First you make the images for the 2 layers. To get a little difference in noise distribution, you should add 0.1 % deviation to the raymarch multiplier before making the second layer.
 
2. Open the 2 images as layers in gimp and combine them once with brighten only and once with darken only. The 2 resulting images should be saved temporarely.

3. Denoise these 2 brightened and darkened images just enough with filters to let the annoying noise disappear.

4. Now open the denoised 2 layers and the 2 first made layers together as 4 layers. Then use the median filter. The result will be much better than the bare denoised images because the sharp contrasts survives while the noise goes.

You can expand this by combining more layers to get even better result. But the work becomes more tedious. But considering the long rendering times it may be worth it.

Here is an example attached. This fractal dissolves if raymarching step is too low. So filtering is the only option.

On the far left of the image is the primary snowy result of mandelbulber.
Left of middle is a commonly denoised blurry section. Looks blurry and painted.
Right of the middle the combination of 2 images made by this method.
On the far right is the result of the step by step combination of 8 images made by this method.
You need to see the image on full zoom to see the ugly snow noise. Sections have a slightly different tone to show borders.
« Last Edit: April 24, 2019, 12:46:55 AM by kohlenstoff »

Offline 3DickUlus

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« Reply #8 on: April 22, 2019, 06:58:10 PM »
http://www.fractalforums.com/animations-showcase-(rate-my-short-animation)/testing-the-water/msg91099/#msg91099



Using mencoder's overcomplete wavelet filter (left side) works well too :D to enable this filter with mencoder use these settings...
Code: [Select]
-vf ow=6:3:3:unsharp=c3x3:0.5:l3x3:0.5
Resistance is fertile... you will be illuminated!

https://en.wikibooks.org/wiki/Fractals/fragmentarium

Offline 1bryan1

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« Reply #9 on: April 23, 2019, 12:40:55 AM »
Gosh, I didn't realize the noise was actually random.
Though I should have worked that out from the "First step random" option.
Stacking the images to identify and reduce noise is something to explore.


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