Forums

Sega Master System / Mark III / Game Gear
SG-1000 / SC-3000 / SF-7000 / OMV
Home - Forums - Games - Scans - Maps - Cheats - Credits
Music - Videos - Development - Hacks - Translations - Homebrew

View topic - Dithering on SMS

Reply to topic
Author Message
  • Joined: 11 Jul 2022
  • Posts: 9
  • Location: Sligo Ireland (and Wales)
Reply with quote
Dithering on SMS
Post Posted: Sun Mar 12, 2023 12:24 am
Last edited by mark_eire on Sun Mar 12, 2023 11:00 pm; edited 1 time in total
In appreciation of dithering effects on SMS I wanted to note a list of some SMS games which make use of this effect.
Online discourse primarily notes use on the Megadrive, but SMS appears to use dithering quite extensively too!

Please post with other game examples below. As I've struggled to find a list elsewhere I figured why not start here.

Noted examples simplified into; "Blending" to create the appearance of additional colours, and "Transparency".

Some SMS games with Dithering (example usually the first found in game but not necessarily the only or best one):
  • Alex Kidd in Miracle World - Blending for bushes in 2nd level
  • Alex Kidd: The Lost Stars - Blending in background sky 1st level
  • Golden Axe Warrior - Blending in trees in overworld
  • GP Rider - Blending in skyline in races
  • KLAX - Blending in lighting of background car park
  • Lemmings - Blending in title of title screen
  • Phantasy Star - Blending in fantastic intro screens
  • [NEW]Shinobi - "Weird luma-chroma crosstalk effect" in stage 2 ("File No. 4523 BLACK TURTLE")
  • Sonic The Hedgehog - Transparency underwater in 2nd level
  • Sonic The Hedgehog 2 - Transparency underwater in Aqua Lake Zone
  • The Ninja - Transparency behind trees in 1st level
  • Wonder Boy III: The Dragon's Trap - Blending for blue colours on "New Game" title screen
  • Ultima IV: Quest of the Avatar - Blending of grass around stone circle in intro


Notes on observing various dithering effects:
  • Varies substantially depending on video output. From RF > Composite > RGB
  • Can vary between TVs.


Additional notes:
  • Wonder Boy in Monster Land has a curious example of a checkerboard pattern which is perhaps not intended for dithering. Via RF on SMSII, the black/white pattern on the table top seen for example in the very first shop does not appear to blend. Perhaps due to being black and white as opposed to other colours? I have no idea, but found the oddity worth mentioning.
  • Composite output of SMS games via Wii VC does not appear to blend at all in any examples I've tested



As I only have an RF SMSII, I'm curious if others find Composite direct from SMS1 has the "blend" effect, or if the visible "checkerboard" appearance remains. The effect appears almost certainly lost in RGB.
Is the Composite output of a modded SMSII the same as an SMS1 taken directly from the video port?


Thanks for reading.
  View user's profile Send private message
  • Joined: 24 Mar 2021
  • Posts: 120
Reply with quote
Post Posted: Sun Mar 12, 2023 12:42 am
On NTSC, the vertical purple and black lines in Shinobi stage 2 ("File No. 4523 BLACK TURTLE") do weird luma-chroma crosstalk effects.
  View user's profile Send private message
  • Joined: 05 Mar 2022
  • Posts: 129
  • Location: Seabrook, New Hampshire
Reply with quote
dithering
Post Posted: Sun Mar 12, 2023 7:13 am
Just an example of dithering with 16 out of 64 colors at 256x192. That's probably at or near the best of what the SMS could display.

  View user's profile Send private message
  • Site Admin
  • Joined: 19 Oct 1999
  • Posts: 14683
  • Location: London
Reply with quote
Post Posted: Sun Mar 12, 2023 7:44 am
Except for the tile count. Random dithering sometimes looks worse on SMS than ordered.
  View user's profile Send private message Visit poster's website
  • Joined: 11 Jul 2022
  • Posts: 9
  • Location: Sligo Ireland (and Wales)
Reply with quote
Post Posted: Sun Mar 12, 2023 11:21 pm
Last edited by mark_eire on Thu Mar 16, 2023 7:01 pm; edited 1 time in total
lidnariq wrote
On NTSC, the vertical purple and black lines in Shinobi stage 2 ("File No. 4523 BLACK TURTLE") do weird luma-chroma crosstalk effects.


That's a fantastic example of a complex video effect! Well beyond my simplistic categorisation of blending dot patterns and transparency.
Do you know how Shinobi is intended to look?
Did you understand this effect to be NTSC only, or had you just not seen PAL? I tested PAL RF SMSII today out of curiosity, while stationary I had rows of alternating Purple and a "new" lighter shade of purple between. Sort of "flickers" when I scroll the screen. Fascinating!

maxxoccupancy wrote
Just an example of dithering with 16 out of 64 colors at 256x192. That's probably at or near the best of what the SMS could display.


That's an impressive looking image, but as Maxim noted I don't think I could tile that up for SMS! Viewing on PC I can't even make sense of what all the dithering on the rear white panels is intended to do. Maximum dither image right there.

Maxim wrote
Random dithering sometimes looks worse on SMS than ordered.


Do you mind explaining the difference there? Is that between clearly defined grids and more scattered patterns (sorta random) to blend colours? Like the difference between the dithering pattern in the sky and letters in the Lemmings title screen?

Noticed in a thread from 2018 Flygon also made a note that "vertical dithering looks terrible on SMS Composite". I'd no appreciation the vertical and horizontal were handled so differently.... Complex topic.
(S) Lemmings.png (19.17 KB)
(S) Lemmings.png

  View user's profile Send private message
  • Site Admin
  • Joined: 19 Oct 1999
  • Posts: 14683
  • Location: London
Reply with quote
Post Posted: Mon Mar 13, 2023 7:53 am
There are a lot of articles about dithering but I suggest to play with http://www.haroldo-ok.com/RgbQuant-SMS.js/RgbQuant-SMS.js/demo/index.html to try out lots of different algorithm options - although it seems to be down now.

Shinobi is likely supposed to look like the arcade game played on an arcade monitor with RGB, ie no artifacts. It seems the lines in question were subtle dark greys in the original, purple on black being an adaptation to the SMS palette.

By their nature, video signals “blur” horizontally but not vertically. Hence the use of vertical lines to get dither/transparency in some systems, but this seems to work better on 320px wide video than 256px.
  View user's profile Send private message Visit poster's website
  • Joined: 05 Sep 2013
  • Posts: 3757
  • Location: Stockholm, Sweden
Reply with quote
Post Posted: Mon Mar 13, 2023 8:42 am
The new URL is https://haroldo-ok.github.io/RgbQuant-SMS.js/RgbQuant-SMS.js/demo/index.html
  View user's profile Send private message Visit poster's website
  • Joined: 24 Mar 2021
  • Posts: 120
Reply with quote
Post Posted: Mon Mar 13, 2023 6:01 pm
mark_eire wrote
Quote
On NTSC, the vertical purple and black lines in Shinobi stage 2 ("File No. 4523 BLACK TURTLE") do weird luma-chroma crosstalk effects.
That's a fantastic example of a complex video effect! Well beyond my simplistic categorisation of blending dot patterns and transparency.
Do you know how Shinobi is intended to look?
I don't know how it's intended to look. On NTSC there's a ... uh, a beat pattern? where we end up with vertical cords that move across the screen much faster than the background itself scrolls. Given that they're "just" houses, it feels to me like that's not intended.

Quote
Did you understand this effect to be NTSC only, or had you just not seen PAL? I tested PAL RF SMSII today out of curiosity, while stationary I had rows of alternating Purple and a "new" lighter shade of purple between. Sort of "flickers" when I scroll the screen. Fascinating!
I hadn't seen PAL at all. A picture or very short video of the behavior on PAL would be awesome, if you would be willing.
  View user's profile Send private message
  • Joined: 11 Jul 2022
  • Posts: 9
  • Location: Sligo Ireland (and Wales)
Reply with quote
Post Posted: Tue Mar 14, 2023 10:31 pm
Thanks very much Maxim, and sverx for the updated link. That website looks great, I think I saw it some time ago regarding tiles but had completely missed the dithering options.

I'm hoping my idea on what counts as random vs ordered dithering as illustrated by the Lemmings screen is sort of right then. If I ever get further along trying to make SMS art myself these are definitely aspects I'd like to play around with.

I do wonder what the intentional look for Shinobi was. I couldn't find the clearest images of the arcade version, but I take your point Maxim, maybe it was a palette limitation. The PAL image does seem to create new colours to my eye.

lidnariq; I tried but failed miserably to record video from the CRT that was in any way legible via digital camera or smartphone. Got a picture though and I can explain how PAL Shinobi looked in motion.

Stationary, you've got a repeating pattern of:
Black line; light Purple; Brigher Purple; light Purple again; Black line. There is a very subtle thinner vertical black line between the purple shades.
Looking closely in motion, the vertical bars are actually fairly stable, but the visible lines all become the lighter purple shade. The Black lines become more defined and the previously barely noticeable line between shades of purple look the same thickness as all the other lines. Any sign of the periodic pattern is completely gone in motion, just repeating black, purple, black, etc.

I wondered if there is any periodicity to the underlying image. Tried to look on Emulicious with PAL and 1:1 Pixel Aspect ratio. At first I thought perhaps, but I think it was more of an optical illusion! Maybe....
IMG_9514.JPG (3.59 MB)
IMG_9514.JPG

  View user's profile Send private message
  • Joined: 05 Mar 2022
  • Posts: 129
  • Location: Seabrook, New Hampshire
Reply with quote
dithering
Post Posted: Thu Mar 16, 2023 12:52 am
Even reducing the tiles to the SMS's 448 maximum (16KB RAM minus the sprite table itself), we would still get some pretty impressive images.

Remember that this image only uses up 56 kilobits (7KB) out of a typical 2,048 kilobit (256KB) ROM cart for the SMS. Even using another 2KB of additional tiles for the car for color blending (like the Sherlock Holmes and other FMV games), we still have ample room left over and enough CPU power to generate somewhat realistic sound for an opening.

There are plenty of nay sayers on this forum, but the SMS was capable of far more than what we saw back in the day.

  View user's profile Send private message
  • Joined: 05 Jun 2010
  • Posts: 757
  • Location: Pennsylvania, USA
Reply with quote
Post Posted: Thu Mar 16, 2023 3:44 am
maxxoccupancy wrote
Even reducing the tiles to the SMS's 448 maximum (16KB RAM minus the sprite table itself), we would still get some pretty impressive images.

Remember that this image only uses up 56 kilobits (7KB) out of a typical 2,048 kilobit (256KB) ROM cart for the SMS. Even using another 2KB of additional tiles for the car for color blending (like the Sherlock Holmes and other FMV games), we still have ample room left over and enough CPU power to generate somewhat realistic sound for an opening.

There are plenty of nay sayers on this forum, but the SMS was capable of far more than what we saw back in the day.


How's that custom FP and VDP hacking going for you?
  View user's profile Send private message Visit poster's website
  • Joined: 05 Sep 2013
  • Posts: 3757
  • Location: Stockholm, Sweden
Reply with quote
Post Posted: Thu Mar 16, 2023 2:03 pm
maxxoccupancy wrote
There are plenty of nay sayers on this forum, but the SMS was capable of far more than what we saw back in the day.


We have no nay sayers that said the full power of the SMS has been already unleashed back in the day. We're already seeing amazing things now and we're going to see more.
  View user's profile Send private message Visit poster's website
  • Joined: 05 Mar 2022
  • Posts: 129
  • Location: Seabrook, New Hampshire
Reply with quote
Post Posted: Thu Mar 16, 2023 3:40 pm
sverx wrote
maxxoccupancy wrote
There are plenty of nay sayers on this forum, but the SMS was capable of far more than what we saw back in the day.


We have no nay sayers that said the full power of the SMS has been already unleashed back in the day. We're already seeing amazing things now and we're going to see more.


The very post above yours. I keep trying to get onto the Genesis/Megadrive fora, but the admins are not responding to new requests.

I may just have to create a new one.

Bottom line is that the SMS was capable of digitized images and much better audio and 3D than we saw.
  View user's profile Send private message
  • Joined: 01 Feb 2014
  • Posts: 844
Reply with quote
Post Posted: Fri Mar 17, 2023 12:30 pm
sverx wrote
We're already seeing amazing things now and we're going to see more.

Indeed, and we’ll see them on actual hardware, not on a fantasy world version of it that only exists in someone’s head.
  View user's profile Send private message
  • Joined: 16 Aug 2018
  • Posts: 5
Reply with quote
Post Posted: Sat Apr 08, 2023 12:40 am
Rainbow banding as caused by the shinobi level is owed to the way color is encoded into the NTSC standard. The long short of it is that the NTSC color standard is basically a forwards compatible hack of the black and white 60hz standard that existed before it. It's forwards compatible, in that it's built ontop of the black and white standard before it, with information that can be ignored to return to the original black and white image. Long story short, the color information is encoded into the original black and white signal and must be separated using fourier transformations to extract the color resolution image inside. The real secret is that luminescence and chrominance share a carrier wave in NTSC. Separating them is a lossy process, and the rainbow artifact is produced due to noise in the signal.

Any color space standard that separates luminescence and chrominance will not yield the rainbow effect. So, the same stage in Shinobi, when viewed with an RGB cable, will not exhibit the rainbow pattern. This also goes for the S-Video standard, and SECAM.
  View user's profile Send private message
Reply to topic



Back to the top of this page

Back to SMS Power!