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NoiseEHC
Registered: Feb 2005
Posts: 51 |
dithering question
Hi!
I have been just looking at recently released MULTI graphics, and what I noticed is that the majority of images use horizontal line dithering. For example:
Always Look at the Bright Side of Life
While in the past most images used checkerboard dithering, for example Hein's graphics in Dutch Breeze. But current example:
Birdman
(Note both images contain both type of dithering, just one is much more dominant.)
And very few use diffuse (random) dithering for some reason.
So what is the reason of this difference? Is it only the preference of the artist, or is there an advantage of horizontal line dithering on a TV? I do not have a real C64 anymore, so I cannot check it unfortunately.
Another question: why are there so few diffuse dithering out there? Is this because this is much harder to do, or is there some visible disadvantage?
Thanks |
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Krill
Registered: Apr 2002
Posts: 2980 |
Something something optional client-side PAL filter on CSDb screenshots... =) |
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NoiseEHC
Registered: Feb 2005
Posts: 51 |
Yeah, but with the above Always Look at the Bright Side of Life image, looking at it via VICE with PAL emulation, there is no color mixing.
Which is expected, as for example it uses black/blue, light-green/cyan. Hmm, maybe that picture was not the best example, I will look at some others... |
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chatGPZ
Registered: Dec 2001
Posts: 11386 |
Mermaid has a couple that exploit it wonderfully <3 |
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ChristopherJam
Registered: Aug 2004
Posts: 1409 |
One thing worth mentioning is that checkerboard dithering in hires is a definite no-no*. It's very close to the colour carrier in both NTSC and PAL (a touch higher than NTSC, a touch lower than PAL). Either way, if you view it using a composite video or RF cable you get spurious colour banding.
Sadly it's not an effect you can safely take advantage of, as the phase is random with every power cycle.
* it's fine in multicolour |
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NoiseEHC
Registered: Feb 2005
Posts: 51 |
Quote: Mermaid has a couple that exploit it wonderfully <3
Yeah, for example this:
No Returns No Refunds All Sales Final
It uses color mixing extensively. However there is very interesting that both the left of the backpack and both the top of the legs use the same dark blue / brown dithering, but the backpack looks greyish in PAL emulation while the legs look purplish. No matter if I resize the window.
https://i.ibb.co/vx3zBL3/pal-emu-differences.png
Is it the same how it looks on a real TV? Why? |
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Oswald
Registered: Apr 2002
Posts: 5094 |
this works because PAL TVs display an average of neighbouring "rasterlines" hue. its a long story, I believe this is done to address a shortcoming of NTSC that came before.
I think main thing not using floyd steinberg style dithering that its simply fugly with brick sized multicolor pixels, it only starts looking good around 320x20 and higher. also FS to work you need larger areas, while in pixeling you want to go from color A to color B usually in short distance. This alternating line dither style is quite recent.
the color mixing the guys are talking above only works for 7 specific color pairs, the colors of the c64 palette which have the same brightness, results are usually strange colors, not usable across wide ranges. |
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ChristopherJam
Registered: Aug 2004
Posts: 1409 |
Quoting NoiseEHCvery interesting that both the left of the backpack and both the top of the legs use the same dark blue / brown dithering, but the backpack looks greyish in PAL emulation while the legs look purplish. ... Why?
The hues for the odd line palette is slightly different to those for the even line palette - if you scroll the picture down a line (eg by writing 3c to $0904 in the viewer), those colours swap. |
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NoiseEHC
Registered: Feb 2005
Posts: 51 |
There is this page which talks about the chroma/luma signals lagging a little:
https://jamontoads.net/p/lumachroma.html
Is this the thing which causes color bleeding? If so then would not it make sense to use it for color transitions? Because it should naturally create a transitional hires pixel between two multi block pixels. Or is it already widely used in pixel graphics? If so why there is not a vertical alternating lines fill prevalent?
And it would be good to get some info from a graphician why prefer horizontal lines over checkerboard patterns in multi mode. Can any of you ping an artist, please?
The reason I ask these questions because I am working on an editor which is a plugin for GIMP. The plan is to draw pictures using my pen tablet, which are converted into 16 color dithered images in real-time. Controlling colors/sprites will be done using some extra layers in the source image. Obviously it will work only if the dithering is good in the first place. |
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Oswald
Registered: Apr 2002
Posts: 5094 |
thats a cool page, VICE should emulate that, totally looks like I remember the screens from back of the days.
Dont think it can be used in graphics much its a subtle subpixel effect. |
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chatGPZ
Registered: Dec 2001
Posts: 11386 |
Color bleeding happens horizontally, while the PAL mixing happens vertically.
And yes, VICE (and every other emu) should emulate it - however, this is something to be implemented in shaders, its way too costly to do in software (if you want to do it correctly) |
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