Banding with colour smudge brushes

Hi!

I thought it was about time I asked about this as it’s been bothering me for years! :kissing_smiling_eyes:

The behaviour of the colour smudge engine seems somewhat unpredictable or inconsistent. The main issue is the banding I get through a brush stroke. It seems to affect flatter brush tips more than round ones, and seems to get more pronounced as I reduce the brush size; This in turn seems to affect the opacity.

I’ve tried to isolate the cause, but not been able to narrow it down - it’s doesn’t seem to be related to pressure sensitivity for example.

Can anyone shed some light on this? - I couldn’t find any mention of it via search.

I’ve made a couple of example pages to demonstrate…

Cheers!

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Test to see if this same behavior occurs in both smearing and dulling mode for the smudge brush.

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I mostly use dulling, but I’ve tested and it happens with smearing too.

Something has just clicked though while I was testing - It’s mostly apparent with textured brushes, but I was just testing with solid brushes and was getting smooth lines until I overlapped the edges of the strokes. I was reading something about the way the colour smudge engine picks up colour in another thread and think that might well explain what’s happening here. :thinking:

It’s seems possible that the brush stroke is interacting with itself and interpreting the textured dab across the breadth of the stroke (from the centre outwards) - causing variable opacity.

I’ll mention it in the other thread and see what the dev thinks…

Hi, @Mythmaker!

Could you please tell me what presets show this problem? Are they present in default presets set or in Digital Atelier?

I’ve just checked Wet Textured Soft. Yes, if I enable a texture for it, then I can see the problem. But that is caused by “Dulling” mode. If I switch to “Smearing Mode” the problem goes away. Actually, there is a warning that this brush is “pierced” so “Dulling” mode is not recommended.

PS:
We don’t have a warning for Dulling Mode + “Pierced Texture”, which might be a problem though.

PPS:
Theoretically, the problem should be solved by activating Smudge Radius option, but it seems like there is a bug in “Smudge Radius” and it doesn’t work for brushes smaller than 100 pixels in size.

Hi, @Mythmaker!

There seem to be a big in Smudge Radius option, it doesn’t work for brushes smaller that 100px. Could you check this build with Dulling+Smudge Radius set to something like 60%?

The brushes will be much slower, but it should fix the problem. If the package does really fix the problem, we can try to fix that in a proper way without speed degradation.

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Hi @dkazakov!

Thanks for looking into this!

I was just doing some more experimentation, and found I couldn’t replicate the banding with smearing mode this time - so I might have made a mistake with my testing yesterday. :blush:

I don’t tend to use smearing because it has a kind of warping quality to it - which might be useful for things like swirling effects, but for a more natural creamy-oily stroke, dulling is much nicer.

I don’t have the atelier brushes - I mostly use my own presets, but the Wet Textured Soft you mentioned is one I keep to hand and relevant to this. I think some of my presets used that as a starting point.

I’m not sure what to do with the file you want me to test? - Is that a window’s installation - I’m on Linux using the 4.2.9 appimage. :innocent:

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I tried the dk1 build and tried using default brushes that involves dulling mode. The ‘Wet Textured Soft’ seemed to look fine, but another brush called ‘SquareSmudge’ seemed to produce banding, even more apparant with smudge radius set higher than the default. I attached an image below:

There seems to be no banding for smearing mode but when I use texture in that mode, the pattern will not be as apparent as dulling mode, it will look smeared, just like what @Mythmaker mentioned . I prefer dulling mode since it keeps the pattern somehow, save for the banding effect. Another imagecomparing the two modes:

I have not tested the Digital Atelier resources but I do have them, just not installed yet. Would it be better if I tested those as well?

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I think flatter tips tend to produce a more pronounced effect - especially textured ones. I favour flatter brushes because they are good for sculpting forms - it’s similar to using flats or filberts with natural media.

Sometimes with texture enabled, even rounder brush can experience banding. Increasing smudge radius may help in some cases, but then somehow it causes brushes to be more transparent.

Okay, I see we mentioned four problems now:

  1. Smudge Radius doesn’t work for brushes < 100px in size
  2. Bigger Smudge Radius makes brush more transparent
  3. Smearing mode with textured brushes smears the texture as well, which is not desired
  4. “Square Smudge” brush behaves weird even with radius option fixed.

Anything else?

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Well… my neighbours dog keeps barking - sometimes it can go on for ages incessantly. It really winds me up! :angry: If you can fix that I’d be eternally grateful! :grinning:

:innocent:

Seriously though - thanks for taking the time to look in to this! It can get frustrating when the brush doesn’t behave in an intuitive way; It’s the main reason I still keep Mypaint to hand - because the smudge brushes in that behave exactly like I expect. I know it’s not really a fair comparison as Krita is more complex - so I’d much prefer not to need Mypaint. I rarely use it now anyway as Krita has improved so much.

p.s. sorry if I’m not being much help at the moment!.. :sweat:

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I don’t think the smeared texture when using smearing mode is actually a problem, it may be useful for bristly effect for oil brush. I think other users like @RamonM, may prefer this effect instead. (I’d like to know what he thinks about this issue overall as well)
I’m just comparing the two modes in regards to the banding effect.

I’m pretty sure there are no more so far.

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Yeah - I think the smear probably behaves as expected. Whether or not I use it is irrelevant - it does what it’s supposed to do (not sure about the banding issue). I actually found it can look pretty cool with the impasto technique I posted - with the right settings it picks out the bristle strokes like raking through wet paint. In general painting it could be useful for things like chrome, marbling, or swirly magical effects - it definitely has it’s place.

Hi, @Mythmaker!

Please check this AppImage with nearest-neighbour algorithm for the texture: https://yadi.sk/d/4NbyB1x7-pCuUw

It is not switchable, just always-forced.

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Okay - I’ve downloaded it ready for testing later! :+1:

Is it safe to use on my main install - it won’t cause any issues with the resource folder etc?

Thanks! :slight_smile:

It should be safe, but better do a backup :slight_smile:

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Okay - I’ve spent a bit of time testing it, but struggling to get my head around it. :thinking:

I think there is a difference, but not sure it’s improving the banding issue. From what I can tell though - the banding might be confined to pierced brushes (and especially flat/chisel type). To be honest - I still don’t know what the definition of a pierced brush is? - I’ve assumed it’s to do with gaps in the tip?

So - I’m starting to wonder if I’m asking for something that’s contrary to how the brush works (as I don’t have any understanding of the underlying algorithms). Hmm… not sure I even understand what I just wrote! :sweat_smile:

Anyway - it’s late and my brain is shutting down! I’ve made a chart with some of the settings I tested. I removed my installed folders so I only had access to default brushes etc.

Oh! - I almost forgot! - One thing I noticed is if I use the line tool then the banding is very uniform (especially with pressure sensitivity off to minimise the variability). That’s not on the chart though…

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Hi, @Mythmaker!

The appimage did not have any banding fixes. It only deals with nearest neighbour option. Please check that, but not the banding.

PS:
I guess we should split the topic into a separate one. There is too much confusion.

Okay - sorry; I’m struggling to understand what you’re referring to! :confused:

I don’t know what nearest neighbour is for? I’ve only encountered that in reference to rescaling. You mentioned it’s for the texture - but is that the brush tip or the pattern (or both!)?! And what issue is it trying to address?

I suppose that could be the scaling of the brush tip? But I’m just guessing…

Well… At least we’ve established and agreed on one thing… It is confusing! :grin:

Okay, when you said about “my neighbours dog keeps barking” I thought you mean the “sharp texture scaling problem” that someone mentioned in a parallel thread. I proposed to solve that with “Nearest Neighbour” algorithm, built a package, but a person said he needs an AppImage. So now I built an AppImage. Now I need to find that person to hand him that AppImage…

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