AuthorTopic: Preventing banding while shading  (Read 3517 times)

Offline CytricAcid

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Preventing banding while shading

on: July 27, 2013, 10:45:47 pm
hello hello! i apologize if this is in the wrong forum. As I'm not really looking for critique on my own art other than general technique, and the fact I'd also like to discuss banding and shading in general, I felt it was best to put it here instead.
One of the problems i have as an artist, within pixel art and out, is cel shading, or at the very least, shading without using soft gradients or any kind of blending. As you can see, this also applies to pixel art as you're working with limited colors. I can shade things with maybe 1 shade and 1 highlight, but past that I find myself getting into banding territory. How do I shade complex objects like torsos and arms without banding, especially in pixel art? what about other complex forms?
I made a quick demonstration on a dragon guy i drew up. I tried to shade him with 4 shades as to test out my own ability. as you can see, there are issues with banding on his leg and tail, along with weird shading on his torso and arm.
I honestly don't know how to go about this. The more shades I add, the easier it is to band my shading. Even when working in higher resolution digital art, I still have problems displaying soft changes in value with a limited palette as to create an illusion of a rounded surface. I want to be able to define my art with more than one shade. How do you guys tackle this?

Offline Pix3M

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Re: Preventing banding while shading

Reply #1 on: July 27, 2013, 11:23:52 pm
I've written something silly addressing this and posted it over at deviantART once.

https://dl.dropboxusercontent.com/u/83822168/web/G/bands.png

(It's an image large enough so I'm posting it as a link and not as an image)

Also, banding is less of a problem if the banding colors have a lower contrast. If the contrast is low enough, my eyes at least won't focus on the band and just look at it as if the colors blend into each other.
« Last Edit: July 27, 2013, 11:26:56 pm by Pix3M »

Offline CytricAcid

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Re: Preventing banding while shading

Reply #2 on: July 28, 2013, 04:25:40 pm
I've written something silly addressing this and posted it over at deviantART once.

https://dl.dropboxusercontent.com/u/83822168/web/G/bands.png

(It's an image large enough so I'm posting it as a link and not as an image)

Also, banding is less of a problem if the banding colors have a lower contrast. If the contrast is low enough, my eyes at least won't focus on the band and just look at it as if the colors blend into each other.
Wow, that's actually really useful! I tried it out on a few other quick line experiments as I didn't feel like cleaning it up much.

it seems that there still seems to be issues with banding at times, especially on the hair of the first one. I also ask the question of using even more shades in order to define high contrast areas and to pull back objects. How does that work, and how does one prevent the pillow shading look when doing so?

Offline Facet

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Re: Preventing banding while shading

Reply #3 on: July 28, 2013, 05:34:35 pm
From a previous thread, excuse the sloppy diagram.

Offline Jeremy

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Re: Preventing banding while shading

Reply #4 on: July 29, 2013, 07:42:37 am
I think the trick is to avoid having a solid band of colour between two different shades (sounds obvious :ouch:)

What I find I end up doing is making sure different tones have quite different "outlines", so my darker colour and lighter colour end up almost touching at a couple of points while the midtone acts kind of like large-scale AA on the sides. I'm sure I've explained that poorly, so here's an example:

(banded version exaggerated)

see how the shape of the red-orage blob is different from the mid orange blob is different from the yellow orange blob:
« Last Edit: July 29, 2013, 08:11:28 am by Jeremy »

Offline questseeker

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Re: Preventing banding while shading

Reply #5 on: July 29, 2013, 10:56:38 am
I think the trick is to avoid having a solid band of colour between two different shades (sounds obvious :ouch:)

What I find I end up doing is making sure different tones have quite different "outlines", so my darker colour and lighter colour end up almost touching at a couple of points while the midtone acts kind of like large-scale AA on the sides. I'm sure I've explained that poorly, so here's an example:

(banded version exaggerated)

see how the shape of the red-orage blob is different from the mid orange blob is different from the yellow orange blob:


The principle of avoiding band shapes is promising in the abstract, but the arm example demonstrates that defining shapes with correct lighting is vastly more important than banding and banding avoidance.
The "banded" version has a more rounded and better looking shoulder, a pillowshaded but reasonably shaped biceps, and a strangely lit but rounded forearm, while the "better" version has stronger and harsher lights (due to the lightest orange clusters being much larger with the darkest orange clusters remaining about the same), abnormally flat biceps and forearm (as if pressed against glass), and the same incoherent light sources.

When the size of banding-related clusters is comparable to the size of the depicted objects, they simply cannot be altered in such arbitrary ways: working at the single pixel level is required to reduce banding without butchering shapes.

Offline Facet

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Re: Preventing banding while shading

Reply #6 on: July 29, 2013, 04:48:18 pm
Yeah, changing the shape of the bands is changing the form; the larger the midtone buffer between light and shade, the more rounded the form. It is something I make a compromise with as well though.

I made another diagram here for one of Charlieton's pieces with the idea of minimising unnecessary/confusing shading by laying down light as simply as possible (light/dark) and adding shades only as needed to round out lights or carve in darks. 



Edit: actually, more to the point are you thinking about edges much? maybe the issue is that you're just adding shades because they're available and not to better describe the form.
« Last Edit: July 29, 2013, 05:06:37 pm by Facet »

Offline CytricAcid

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Re: Preventing banding while shading

Reply #7 on: July 29, 2013, 07:24:50 pm
I've been trying to think in more of putting down absolutes then adding midtones, yes. I find it rather hard to do though when working with animals than with humans, and since I like to draw dragons, I'm often stuck on adding shades to my drawing to portray a rounded form without it banding, especially on head shapes and the body.
that being said, i'm a bit confused on thinking of edges. What do you mean? I do agree that i try to add shades just because they're there, but I feel that when I don't, my shading often looks rather flat.

Offline Facet

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Re: Preventing banding while shading

Reply #8 on: July 29, 2013, 09:39:10 pm
If the lighting is accurate it should feel dimensional with the minimum of shades, severely limited palletes are a great way to practice.
 
By edges I just mean the abruptness of the transition from one colour to another; it's an important part of painting and there's tons of stuff to read on this if you search for it. Harder being less transition, softer more.
 
The most fundamental consideration is the curvature of form though; how abrupt is the plane change = how abrupt your edge should be; sounds self evident but it's easy enough to default to rendering everything alike if not kept in mind. By extension the edges of cast shadows are usually harder (because they're flat) but soften with distance from source.

Probably the simplest way to avoid obvious bands is just to vary the spacing of your values (giving them irregular range) and/or shading; notice I used a wider band in my corner examples in place of more shades like a sort of 'low poly' curve interpretation, not sure why this wasn't mentioned last time actually :lol:.



Edit: that right-hand bit of the diagram/bumf wasn't very clear. fixt better
« Last Edit: July 31, 2013, 10:52:25 pm by Facet »

Offline PixelPiledriver

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Re: Preventing banding while shading

Reply #9 on: July 30, 2013, 12:34:07 am
You're using mostly overlapping shapes.
Try interlocking shapes and opposing directions.







« Last Edit: July 30, 2013, 05:42:26 am by PixelPiledriver »
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